Notes on Iberian parasitic Plagiolepis Mayr 1861 ants, with the first Iberian records for Plagiolepis ampeloni (Faber, 1969) (Hymenoptera: Formicidae)
Notas sobre las hormigas Plagiolepis Mayr, 1861 parásitas en la península ibérica, las primeras citas ibéricas para Plagiolepis ampeloni (Faber, 1969) (Hymenoptera, Formicidae)
Fede García
Investigador independiente. C/ Blesa, 45, 08004, Barcelona
chousas2@gmail.com, https://orcid.org/0009-0007-5647-399X
Amonio David Cuesta-Segura
Investigador independiente. C/ Río Oca, 19, E-09240, Briviesca, Burgos, Spain
dcuesta.bugman@gmail.com, https://orcid.org/0000-0001-8868-4934
Xavier Espadaler
CREAF. Edificio C. Universidad Autónoma de Barcelona. 08193, Cerdanyola del Vallès, Barcelona
xavierespadaler@gmail.com, https://orcid.org/0000-0002-7681-5957
ABSTRACT
The ant genus Plagiolepis Mayr, 1861 includes five social parasites, with two of these species being known in Iberia so far, Plagiolepis grassei Le Masne, 1956 and Plagiolepis xene Stärcke, 1936, with a third parasitic species for the Peninsula, Plagiolepis ampeloni (Faber, 1969) being added in this work. The known distribution of the three parasitic Plagiolepis known to inhabit in the Iberian Peninsula is reviewed and new records are presented. The morphology of all species is discussed and a more precise description of all castes of P. grassei is presented, since a formal description of the species was never published.
Keywords: distribution, Formicidae, Hymenoptera, Plagiolepis, social parasite.
RESUMEN
El género de hormigas Plagiolepis Mayr, 1861 incluye cinco especies parásitas sociales. Dos de estas especies, Plagiolepis grassei Le Masne, 1956 y Plagiolepis xene Stärcke, 1936, ya se conocían en la península ibérica. En este trabajo se añade una tercera especie parásita, Plagiolepis ampeloni (Faber, 1969). Se revisa la distribución conocida de las tres especies parásitas de Plagiolepis que habitan en la península ibérica y se presentan citas nuevas. Se discute la morfología de todas las especies y se ofrece una descripción más precisa de todas las castas de P. grassei, dado que nunca se publicó una descripción formal de la especie.
Palabras clave: distribución, Formicidae, Hymenoptera, parásito social, Plagiolepis.
Received: 21-11-2025 / Accepted: 09-06-2026 / Published: 29-07-2026
Citation: García, F., Cuesta-Segura, A.D. & Espadaler, X. 2026. Notes on Iberian parasitic Plagiolepis Mayr 1861 ants, with the first Iberian record for Plagiolepis ampeloni (Faber, 1969) (Hymenoptera: Formicidae). Graellsia, 82 (1-2): e818. https://doi.org/10.3989/graellsia.2026.v82.818
Copyright: © 2026 SAM & CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License.
Supplementary information ↓
CONTENIDO
3.1. Plagiolepis ampeloni (Faber, 1969)
3.2. Plagiolepis xene Stärcke, 1936
3.3. Plagiolepis grassei (Le Masne, 1956)
1. INTRODUCTION
The ant genus Plagiolepis Mayr 1861 includes 67 extant species (Bolton, 2025Bolton, B., 2025. Antcat. Plagiolepis. Available ffom https://www.antcat.org/catalog/429205qq=Plagiolepis [accessed 22 May 2024].), characterized for their small size (Borowiec & Salata, 2022Borowiec, L. & Salata, S., 2022. A monographic review of ants of Greece (Hymenoptera: Formicidae). Vol. 1. Introduction and review of all subfamilies except the subfamily Myrmicinae. Part 1: text. Natural History Monographs of the Upper Silesian Museum. Bytom. 297 pp.). Five species distributed in Europe and Central Asia are inquiline social parasites (Buschinger, 2009Buschinger, A., 2009. Social parasitism among ants: a review. Myrmecological News, 12: 219-235. https://doi.org/10.25849/myrmecol.news_012:219), with some additional inquiline taxa remaining undescribed (Seifert, 2020Seifert, B., 2020. Revision of the Plagiolepis schmitzii group with description of Pl. invadens sp. nov. -a new invasive supercolonial species (Hymenoptera: Formicidae). Deutsche Entomologische Zeitschrift, 67 (2): 183-196. https://doi.org/10.3897/dez.67.53199). Phylogenetic evidence indicates that these inquilines do not form a monophyletic group, but rather originated through multiple independent speciation events, with each parasite being closely related to its free-living host species (Degueldre et al., 2021Degueldre, F., Mardulyn, P., Kuhn, A., Pinel, A., Karaman, C., Lebas, C., Schifani, E., Bračko, G., Wagner, H.C., Kiran, K., Borowiec, L., Passera, L., Abril, S., Espadaler, X. & Aron, S., 2021. Evolutionary history of inquiline social parasitism in Plagiolepis ants. Molecular Phylogenetics and Evolution, 155: 107016 https://doi.org/10.1016/j.ympev.2020.107016). These inquilines have small sexuates relative to the free-living Plagiolepis, and lack in most cases the worker caste.
Until now, two species of parasitic Plagiolepis were known from Iberia: Plagiolepis xene Stärcke, 1936 and Plagiolepis grassei Le Masne, 1956 (e.g., García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.). Both species are parasites of Plagiolepis pygmaea (Latreille, 1798) (Degueldre et al., 2021Degueldre, F., Mardulyn, P., Kuhn, A., Pinel, A., Karaman, C., Lebas, C., Schifani, E., Bračko, G., Wagner, H.C., Kiran, K., Borowiec, L., Passera, L., Abril, S., Espadaler, X. & Aron, S., 2021. Evolutionary history of inquiline social parasitism in Plagiolepis ants. Molecular Phylogenetics and Evolution, 155: 107016 https://doi.org/10.1016/j.ympev.2020.107016), although P. xene has also been reported associated with other host species (Tinaut et al., 2009Tinaut, A., Mira, O., Vidal, J.M. & Aguirre-Segura, A., 2009. Las hormigas de Cabo de Gata (Almería, España), aspectos faunísticos (Hymenoptera, Formicidae). Boletín de la Asociación Española de Entomología, 33 (1-2): 227-251.; Seifert, 2018Seifert, B., 2018. The Ants of Central and North Europe. Lutra Verlags, Tauer. 408 pp.). In addition, an undescribed species resembling P. grassei, whose records were published under this name, has also been mentioned in the literature (Catarineu et al., 2018Catarineu, C., Barberá, G.G. & Reyes-López, J.L., 2018. Zoogeography of the Ants (Hymenoptera: Formicidae) of the Segura River Basin. Sociobiology, 65: 383-396. https://doi.org/10.13102/sociobiology.v65i3.2822; García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.).
In this work, we report a third inquiline Plagiolepis for Iberia, which we attribute to Plagiolepis ampeloni (Faber, 1969Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100.). We also review and expand the known Iberian distribution of P. xene by providing new records. Finally, we provide photographs and comments about the morphology of the three castes of P. grassei, a species that remained largely without a precise morphological description (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].).
2. MATERIAL AND METHODS
The specimens studied in this work were collected in Spain. No specific methodology was followed for capturing Plagiolepis. The samplings were carried out along several years and places, involving different objectives and varied methodologies that doesn’t affect the faunistic records presented here. Specimens were captured mainly through direct sampling, by searching for ant nests, typically under stones. Some of the sexuates were found after drowning in small bodies of water (e.g., ponds). One gyne was collected in Ruesga (Cervera de Pisuerga) from 64 plastic pitfall traps (140 mm deep, 90 mm in diameter) that were placed to capture arachnids from June 14 to 27, 2025; and two gynes in Cevico de la Torre from six plastic pitfall traps (88 mm deep, 65 mm in diameter) that were placed to capture ants and were replaced approximately every 20 days from June 8 to November 11, 2023.
Precise data about the new localities is provided in the Results section. The material examined comprises the following:
- P. ampeloni: 11 gynes from Albacete, Ávila and Huesca provinces.
- P. xene: 23 gynes and 1 male captured from several published and unpublished (detailed in the Results section) localities in the provinces of Barcelona, Burgos, Cádiz, Huesca, León, Palencia, Segovia and València.
- P. grassei: 13 workers, 14 gynes and one male, from 3 known localities in Barcelona province: Montjuïc (1 worker, 7 gynes, 1 male), Collserola (7 workers), Garraf (2 workers, 3 gynes) (García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.) and a new population in Monistrol de Montserrat.
- Plagiolepis pyrenaica Emery, 1921: 6 workers from the Spanish provinces of Albacete, Ávila and Huesca.
- P. pygmaea: 36 workers captured from colonies containing P. xene and P. grassei and from non-parasitized colonies in many other localities in the provinces of Barcelona, Burgos, Cádiz, Huesca, León, Lleida, Lugo, Palencia, Pontevedra, Segovia, Tarragona and València.
In addition, type material from Plagiolepis pygmaea var. pyrenaica Emery, 1921 from Banyuls-sur-Mer was also compared with samples (workers, gynes and males) from Saint-Cyprien plage (France; 4/IV/2008; X. Espadaler leg.), approximately 16 km from the type locality.
All the specimens are deposited dry mounted or in ethanol 96% in the FG, ADC-S and XE personal collections, except for one gyne of P. ampeloni and several workers and gynes of P. grassei which are stored in absolute ethanol in M. Menchetti’s collection.
Biometrical measurements were taken using an ocular micrometer at a magnification of 90×. These are detailed hereafter. CL: cephalic length, from the anterior margin of the clypeus to occipital margin of the head; CW: maximum cephalic width, either across or above the eyes; CS: cephalic size, mean of CL and CW; PoOC: postocular distance, from the posterior margin of the eyes to the occipital margin of the head; SL: maximum scape length; EL: maximum length of the eye; ML: maximum length of mesosoma in lateral view (in workers, from the anteriormost point of the pronotum to the posterior point of metapleural gland; in gynes, from anterior angle of the scutum to the posterior point of the metapleural gland); MW: maximum width of the mesosoma in dorsal view across the pronotum; sqPDG: square root of the mean distance of the pubescence on dorsomedian surface of 1st gaster tergite, measured counting the number of hairs (n) crossing a line of L longitude (n/L).
Bibliographic records for the Iberian Peninsula and Balearic Islands were compiled using the AntMaps database (Guénard et al., 2017Guénard, B., Weiser, M., Gómez, K., Narula, N. & Economo, E.P., 2017. The Global Ant Biodiversity Informatics (GABI) database: a synthesis of ant species geographic distributions. Myrmecological News, 24: 83-89.) through the www.antmaps.org interface (Janicki et al., 2016Janicki, J., Narula, N., Ziegler, M., Guénard, B. & Economo, E.P., 2016. Visualizing and interacting with large-volume biodiversity data using client-server web-mapping applications: The design and implementation of antmaps.org. Ecological Informatics, 32: 185-193. https://doi.org/10.1016/j.ecoinf.2016.02.006) and Google Scholar. Distribution maps were generated with QGIS software (QGIS, 2022QGIS development team. 2022. QGIS Geographic Information System. Open Source Geospatial Foundation Project. Versión 3.44. Available from https://qgis.org [accessed 6 Oct. 2024].). The author of all the photographs is Fede García.
3. RESULTS AND DISCUSSION
3.1. Plagiolepis ampeloni (Faber, 1969)
Plagiolepis ampeloni is a very scarce inquiline species with apterous and alate forms in both sexes (Faber, 1969Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100.). There are published records from Austria (Faber, 1969Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100.), Italy (Buschinger, 1999Buschinger A., 1999. Bemerkenswerte Ameisenfunde aus Südtirol (Hymenoptera: Formicidae). Myrmecologische Nachrichten, 3: 1-8.), Slovakia (Bezdecka, 1996Bezdecka, P., 1996. The ants of Slovakia (Hymenoptera: Formicidae). Entomofauna Carpathica, 8: 108-114.; Werner & Wiezik, 2007Werner, P. & Wiezik, M., 2007. Vespoidea: Formicidae (mravencovití). Acta Entomologica Musei Nationalis Pragae. Supplementum, 11: 133-164.), Hungary (Kanizsai et al., 2009Kanizsai, O., Gallé, R. & Gallé, L., 2009. Perception of spatial patchiness by ant assemblages (Hymenoptera: Formicidae). Tiscia, 37: 3-7.; Csősz et al., 2011Csősz S., Markó, B. & Gallé, L., 2011. The myrmecofauna (Hymenoptera: Formicidae) of Hungary: an updated checklist. North-Western Journal of Zoology, 7: 55-62.), Slovenia (Bračko, 2007Bračko, G., 2007. Checklist of the ants of Slovenia (Hymenoptera: Formicidae). Natura Sloveniae, 9: 15-24. https://doi.org/10.14720/ns.9.1.15-24) and Turkey (Heinze & Kauffmann, 1993). With the exception of the original description by Faber (1969)Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100., these records generally lack additional morphological information and consist mainly of faunistic listings. The species was recorded from Cyprus by Georgiadis et al. (2017)Georgiadis, C., Leonidou, K., Tsipouridou, C. & Legakis, A., 2017. The ant fauna of Cyprus. In: Lytra,I. & Perdikis, D. (Eds.). Book of Abstracts. 17th Panhellenic Entomological Congress, Athens, 19–22 September 2017. Agricultural University of Athens. Atenas: 51. https://doi.org/10.13140/RG.2.2.19289.01123, but later Demetriou et al. (2024)Demetriou, J., Georgiadis, C., Ralli, V., Salata, S. & Borowiec, L., 2024. Setting the record straight: a re-examination of ants (Hymenoptera: Formicidae) from Cyprus deposited at the Museum of Zoology of Athens. Zootaxa, 5523 (1): 49-69. https://doi.org/10.11646/zootaxa.5523.1.3. showed that the records were based on misidentifications and removed the species from the island list.
Plagiolepis ampeloni was listed as vulnerable in the UICN Red List (Social Insects Specialist Group, 1996aSocial Insects Specialist Group., 1996a. Plagiolepis ampeloni. The IUCN Red List of Threatened Species 1996: e.T17465A7087429. https://doi.org/10.2305/IUCN.UK.1996.RLTS.T17465A7087429.en). The last captures in the type locality date back to the 1970s, being probably extinct there due to habitat destruction (Schlick-Steiner et al., 2003Schlick-Steiner, B.C., Steiner, F.M. & Schödl, S., 2003. Rote Listen ausgewählter Tiergruppen Niederösterreichs. Ameisen (Hymenoptera: Formicidae). 1. Fassung 2002. St. Pölten: Amt der Niederösterreichischen Landesregierung, Abteilung Naturschutz, 75 pp.).
The following are the first confirmed records of P. ampeloni for the Iberian Peninsula:
ALBACETE: Laguna Ojos de Villaverde. 12/IV/1989, 38.8° N, 2.3°W. Four apterous gynes in nest of P. pyrenaica, X. Espadaler leg.
ÁVILA: La Torre. 22/VI/2024, 40.59° N, 4.96°W, 1140 m.a.s.l., hillside with grass and small shrubs, with many paths for sheep to pass through. Three apterous gynes (Fig. 1), under stone in a nest of P. pyrenaica (Fig. 2), together with males. A.D. Cuesta-Segura leg. The specimens were collected incidentally while sampling other ant species, and the presence of the parasite was not noted at the site. Therefore, the number of parasitic gynes should not be taken as an indication of frequency in the colony.
Figure 1. Plagiolepis ampeloni gyne from Ávila: a) habitus, lateral view; b) head, frontal view; c) mesosoma and petiole, dorsal view. Scales: 250 µm.
Figura 1. Reina de Plagiolepis ampeloni de Ávila: a) hábitus, vista lateral; b) cabeza, vista frontal; c) mesosoma y peciolo, vista dorsal. Escalas: 250 µm.
Figure 2. Plagiolepis pyrenaica from Ávila: a) head, frontal view; b) gaster, dorsal view. Scales: 250 µm.
Figura 2. Plagiolepis pyrenaica de Ávila: a) cabeza, vista frontal; b) gáster, vista dorsal. Escalas: 250 µm.
HUESCA: Sariñena. 10/V/1986, 41.7° N, 0.1°W. Eight apterous gynes in nest of P. pyrenaica, X. Espadaler leg.
These new records are about 1400 km away from the nearest known location in Italy (Buschinger, 1999Buschinger A., 1999. Bemerkenswerte Ameisenfunde aus Südtirol (Hymenoptera: Formicidae). Myrmecologische Nachrichten, 3: 1-8.). The fact that only apterous gynes were collected may be related to the sampling period, which did not coincide with the presence of newly produced sexuates in the nests, known to occur in mid-August (Faber, 1969Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100.).
We ascribe the samples to P. ampeloni given the morphological and biometrical similarity of the Iberian specimens with the apterous gynes described by Faber (1969)Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100.. Among the characters that differentiate P. ampeloni from other parasitic Plagiolepis stand out the mandibular edge without defined teeth except an apical one, the eyes situated higher in frontal view (Seifert, 2018Seifert, B., 2018. The Ants of Central and North Europe. Lutra Verlags, Tauer. 408 pp.), a comparatively less elongated head and a slender mesosoma (Faber, 1969Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100.; Table 1). The only apparent difference we note in the Iberian specimens with respect to the Austrian ones described by Faber (1969)Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100. concerns the shape of the scutum, which shows more rounded borders, and lacks the trapezoidal shape noted by Faber (1969)Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100..
Host species have been reported in only two previous records of P. ampeloni, both involving Plagiolepis vindobonensis Lomnicki, 1925 (Faber, 1969Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100.; Buschinger, 1999Buschinger A., 1999. Bemerkenswerte Ameisenfunde aus Südtirol (Hymenoptera: Formicidae). Myrmecologische Nachrichten, 3: 1-8.), currently a junior synonym of Plagiolepis taurica Santschi, 1920 (Kirschner et al., 2023Kirschner, P., Seifert, B., Kröll, J., The STEPPE Consortium, Schlick-Steiner, B.C. & Steiner, F.M., 2023. Phylogenomic inference and demographic model selection suggest peripatric separation of the cryptic steppe ant species Plagiolepis pyrenaica stat. rev. Molecular Ecology, 32 (5): 1149-1168. https://doi.org/10.1111/mec.16828).
The complicated history of the group in Iberia and elsewhere deserves a brief overview. Because of a similar morphology of the antennal funicles, Iberian pallescens group samples were for a long time confused with Plagiolepis schmitzii Forel, 1895 in the Iberian ant bibliography (e.g., Collingwood, 1978Collingwood, C.A., 1978. A provisional list of lberian Formicidae with a key to the worker caste (Hym. Aculeata). Eos: Revista Española de Entomología, 52 (1-4): 65-95.). Espadaler et al. (2013)Arcos, J., Espadaler, X. & Catarineu, C., 2013. Nuevas citas de Temnothorax cristinae (Espadaler, 1997) para el sureste de la península ibérica y ampliación de su descripción. Iberomyrmex, 5: 5-8. were the first to establish the presence of the group in Iberia under the name P. taurica. Later, Tinaut & García (2018) re-examined the Andalusian samples formerly identified as P. schmitzii, identifying half of them as P. taurica. More recently, western populations were assigned to P. pyrenaica (Kirschner et al., 2023Kirschner, P., Seifert, B., Kröll, J., The STEPPE Consortium, Schlick-Steiner, B.C. & Steiner, F.M., 2023. Phylogenomic inference and demographic model selection suggest peripatric separation of the cryptic steppe ant species Plagiolepis pyrenaica stat. rev. Molecular Ecology, 32 (5): 1149-1168. https://doi.org/10.1111/mec.16828), with P. taurica having an eastern distribution that includes the type locality of P. ampeloni. Although Kirschner et al. (2023)Kirschner, P., Seifert, B., Kröll, J., The STEPPE Consortium, Schlick-Steiner, B.C. & Steiner, F.M., 2023. Phylogenomic inference and demographic model selection suggest peripatric separation of the cryptic steppe ant species Plagiolepis pyrenaica stat. rev. Molecular Ecology, 32 (5): 1149-1168. https://doi.org/10.1111/mec.16828 did not study Iberian specimens, the proximity of the type locality of P. pyrenaica to the French-Spanish border and the biometric concordance of the Iberian specimens are in accordance with the diagnostic framework proposed by the latter authors.
Given the morphological similarities between the parasitic Plagiolepis gynes from Iberia and the accurate description by Faber (1969)Faber, W., 1969. Beiträge zur Kenntnis sozialparasitischer Ameisen. 2. Aporomyrmex ampeloni nov. gen., nov. spec. (Hym. Formicidae), ein neuer permanenter Sozialparasit bei Plagiolepis vindobonensis Lomnicki aus Österreich. Pflanzenschutz Berichte, 39: 39-100. we do not consider the description of a new species justified at this stage, despite the association with a different host than P. taurica. In fact, the record from South Tyrol (Buschinger, 1999Buschinger A., 1999. Bemerkenswerte Ameisenfunde aus Südtirol (Hymenoptera: Formicidae). Myrmecologische Nachrichten, 3: 1-8.) may fall within the distribution area of P. pyrenaica, being very close to the distributional limits between both species (Kirschner et al., 2023Kirschner, P., Seifert, B., Kröll, J., The STEPPE Consortium, Schlick-Steiner, B.C. & Steiner, F.M., 2023. Phylogenomic inference and demographic model selection suggest peripatric separation of the cryptic steppe ant species Plagiolepis pyrenaica stat. rev. Molecular Ecology, 32 (5): 1149-1168. https://doi.org/10.1111/mec.16828). Moreover, some degree of host plasticity is not rare in many inquiline social parasites, even at a regional level, for example Tetramorium atratulum (Schenck, 1852) and Strongylognathus testaceus (Schenck, 1852) (Wagner et al., 2017Wagner, H.C., Arthofer, W., Seifert, B., Muster, C., Steiner, F.M. & Schlick-Steiner, B.C., 2017. Light at the end of the tunnel: Integrative taxonomy delimits cryptic species in the Tetramorium caespitum complex (Hymenoptera: Formicidae). Myrmecological News, 25: 95-129. https://doi.org/10.25849/myrmecol.news_025:095), Myrmica karavajevi Arnoldi, 1930 (Radchenko & Elmes, 2003Radchenko, A.G. & Elmes, G.W., 2003. A taxonomic revision of the socially parasitic Myrmica ants (Hymenoptera: Formicidae) of the Palaearctic region. Annales Zoologici, 53: 217-243.) or even parasitic species within Plagiolepis itself (e.g., P. xene; Seifert, 2018Seifert, B., 2018. The Ants of Central and North Europe. Lutra Verlags, Tauer. 408 pp.).
Finally, given that the only detailed morphological study on the species is based on a single population coming from the original description, currently we do not have any knowledge about the possible geographic variability of the species.
The lack of a comprehensive revision of historical Iberian records formerly attributed to P. schmitzii, also results in incomplete knowledge of the distribution of P. pyrenaica which nonetheless appears to be widespread in the Iberian Peninsula (Fig. 3). In the future, myrmecologists must check the nests of P. pyrenaica, as it is already routinely done for P. pygmaea and its parasites.
Table 1: Biometric measurements and indexes for four Plagiolepis species studied in this work.
Tabla 1: Medidas e índices biométricos para cuatro especies de Plagiolepis estudiadas en este trabajo.
|
Species |
P. ampeloni |
P. xene |
P. xene |
P. grassei |
P. grassei |
P. grassei |
P. pygmaea |
|
Caste |
gyne |
gyne |
male |
gyne |
male |
worker |
worker |
|
n |
11 |
23 |
1 |
14 |
1 |
13 |
36 |
|
CS (microns) |
365.9 ± 11.2 (339; 382) |
358.5 ± 7.9 (345; 376) |
345 |
420.6 ± 7.9 (407; 430) |
344.5 |
375.5 ± 9.88 (351; 396) |
420 ± 28 (379; 486) |
|
CL/CW |
1.003 ± 0.03 (0.937; 1.045) |
1.042 ± 0.03 (1; 1.100) |
1.032 |
1.059 ± 0.03 (1.0; 1.084) |
1.032 |
1.101 ± 0.03 (1.061; 1.145) |
1.123 ± 0.04 (1.049; 1.182) |
|
SL/CS |
0.887 ± 0.02 (0.847; 0.913) |
0.867 ± 0.03 (0.814; 0.921) |
0.952 |
0.905 ± 0.02 (0.879; 0.947) |
0.952 |
0.901 ± 0.01 (0.885; 0.923) |
0.914 ± 0.02 (0.865; 0.954) |
|
POOC/CL |
0.437 ± 0.02 (0.410; 0.469) |
0.421 ± 0.02 (0.394; 0.456) |
0.389 |
0.407 ± 0.02 (0.385; 0.447) |
0.389 |
0.426 ± 0.01 (0.399; 0.443) |
0.394 ± 0.01 (0.376; 0.418) |
|
EL/CS |
0.246 ± 0.02 (0.212; 0.296) |
0.303 ± 0.02 (0.257; 0.336) |
0.328 |
0.299 ± 0.01 (0.273; 0.321) |
0.328 |
0.246 ± 0.02 (0.208; 0.271) |
0.247 ± 0.01 (0.228; 0.272) |
|
CS/ML |
0.791 ± 0.03 (0.732; 0.833) |
0.716 ± 0.03 (0.678; 0.768) |
0.663 |
0.684 ± 0.03 (0.643; 0.736) |
0.663 |
0.852 ± 0.02 (0.825; 0.885) |
0.877 ± 0.03 (0.815; 0.931) |
|
MW/CS |
0.674 ± 0.03 (0.635; 0.724) |
0.769 ± 0.02 (0.724; 0.808) |
0.952 |
0.888 ± 0.03 (0.837; 0.943) |
0.952 |
0.643 ± 0.02 (0.625; 0.676) |
0.617 ± 0.02 (0.574; 0.672) |
|
MW/ML |
0.533 ± 0.03 (0.488; 0.575) |
0.551 ± 0.02 (0.510; 0.575) |
0.631 |
0.608 ± 0.04 (0.552; 0.679) |
0.631 |
0.549 ± 0.02 (0.524; 0.598) |
0.541 ± 0.02 (0.498; 0.595) |
|
sqPDG |
4.489 ± 0.20 (4.339; 4.754) |
4.130 ± 0.25 (3.758; 4.754) |
— |
4.412 ± 0.25 (4.018; 4.754) |
— |
4.588 ± 0.26 (4.018; 4.754) |
3.928 ± 0.32 (3.205; 4.339) |
Figure 3. Map of the known Iberian and Balearic records for Plagiolepis pyrenaica (yellow circles), P. ampeloni (red squares) and non revised records for P. schmitzii (green circles).
Figura 3. Mapa de las citas ibéricas y baleares conocidas de Plagiolepis pyrenaica (círculos amarillos), P. ampeloni (cuadrados rojos) y citas no revisadas de P. schmitzii (círculos verdes).
3.2. Plagiolepis xene Stärcke, 1936
Plagiolepis xene is an inquiline social parasite lacking workers (Aron et al., 1999Aron, S., Passera, L. & Keller, L., 1999. Evolution of social parasitism in ants: size of sexuals, sex ratio and mechanisms of caste determination. Proceedings of the Royal Society of London, 266: 173-177. https://doi.org/10.1098/rspb.1999.0618). Its known host species are P. pygmaea and P. pyrenaica (Seifert, 2018Seifert, B., 2018. The Ants of Central and North Europe. Lutra Verlags, Tauer. 408 pp.). The species is widely distributed along southern Europe, with many records ranging from Iberia to Turkey and Ukraine (Borowiec & Salata, 2022).
About fifty records of P. xene are known from Iberia, the vast majority associated with P. pygmaea as host, although there is a finding with P. schmitzii (Tinaut et al., 2009Tinaut, A., Mira, O., Vidal, J.M. & Aguirre-Segura, A., 2009. Las hormigas de Cabo de Gata (Almería, España), aspectos faunísticos (Hymenoptera, Formicidae). Boletín de la Asociación Española de Entomología, 33 (1-2): 227-251.). However, this record should be interpreted with caution, considering the history of confusion of P. schmitzii with P. pyrenaica, as discussed above.
In mainland Spain, P. xene has been recorded from the provinces of Alicante (Arcos et al., 2013Arcos, J., Espadaler, X. & Catarineu, C., 2013. Nuevas citas de Temnothorax cristinae (Espadaler, 1997) para el sureste de la península ibérica y ampliación de su descripción. Iberomyrmex, 5: 5-8.); Almería (Tinaut et al., 2009Tinaut, A., Mira, O., Vidal, J.M. & Aguirre-Segura, A., 2009. Las hormigas de Cabo de Gata (Almería, España), aspectos faunísticos (Hymenoptera, Formicidae). Boletín de la Asociación Española de Entomología, 33 (1-2): 227-251.); Barcelona (Espadaler, 1979Espadaler, X., 1979. Citas nuevas o interesantes de hormigas (Hym. Formicidae) para España. Boletín de la Asociación Española de Entomología, 3: 95-101.; Restrepo et al., 1985Restrepo, C., Espadaler, X. & De Haro, A., 1985. Contribución al conocimiento faunístico de los formícidos del Macizo de Garraf (Barcelona). Orsis, 1: 113-129.; Espadaler & López-Soria, 1991Espadaler, X. & López-Soria, L., 1991. Rareness of certain Mediterranean ant species: fact or artifact? Insectes Sociaux, 38: 365-377. https://doi.org/10.1007/BF01241872; Bernal, 2015Bernal, V.C., 2015. Efecto de la fragmentación de los bosques de la Plana del Vallès sobre la fauna mirmecológica. Universitat Autònoma de Barcelona. Thesis. 180 pp.; García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.; Degueldre et al., 2021Degueldre, F., Mardulyn, P., Kuhn, A., Pinel, A., Karaman, C., Lebas, C., Schifani, E., Bračko, G., Wagner, H.C., Kiran, K., Borowiec, L., Passera, L., Abril, S., Espadaler, X. & Aron, S., 2021. Evolutionary history of inquiline social parasitism in Plagiolepis ants. Molecular Phylogenetics and Evolution, 155: 107016 https://doi.org/10.1016/j.ympev.2020.107016; Herraiz & Espadaler, 2022); Burgos (García & Cuesta-Segura, 2017Georgiadis, C., Leonidou, K., Tsipouridou, C. & Legakis, A., 2017. The ant fauna of Cyprus. In: Lytra,I. & Perdikis, D. (Eds.). Book of Abstracts. 17th Panhellenic Entomological Congress, Athens, 19–22 September 2017. Agricultural University of Athens. Atenas: 51. https://doi.org/10.13140/RG.2.2.19289.01123); Cádiz (Degueldre et al., 2021Degueldre, F., Mardulyn, P., Kuhn, A., Pinel, A., Karaman, C., Lebas, C., Schifani, E., Bračko, G., Wagner, H.C., Kiran, K., Borowiec, L., Passera, L., Abril, S., Espadaler, X. & Aron, S., 2021. Evolutionary history of inquiline social parasitism in Plagiolepis ants. Molecular Phylogenetics and Evolution, 155: 107016 https://doi.org/10.1016/j.ympev.2020.107016); Castelló (Espadaler, 1997aEspadaler, X., 1997a. Catàleg de les formigues (Hymenoptera, Formicidae) del països catalans. Institució Catalana d’Història Natural. Sessió Conjunta d’Entomologia, 9: 23-42.); Ciudad Real (Obregón & Reyes-López, 2015Obregón, R. & Reyes-López, J.L., 2015. Primera aproximación a la mirmecocenosis (Hymenoptera, Formicidae) de Sierra Madrona (Ciudad real, España). Boletín de la Sociedad Entomológica Aragonesa, 56: 191-194.); Girona (Degueldre et al., 2021Degueldre, F., Mardulyn, P., Kuhn, A., Pinel, A., Karaman, C., Lebas, C., Schifani, E., Bračko, G., Wagner, H.C., Kiran, K., Borowiec, L., Passera, L., Abril, S., Espadaler, X. & Aron, S., 2021. Evolutionary history of inquiline social parasitism in Plagiolepis ants. Molecular Phylogenetics and Evolution, 155: 107016 https://doi.org/10.1016/j.ympev.2020.107016); Granada (Pascual, 1986Pascual, M.R., 1986. Estudio taxonómico y ecológico de los Formícidos de las Sierras de Alfacar, La Yedra, Huétor y Harana. Universidad de Granada, Departamento de Biología Animal, Ecología y Genética. Tesis doctoral. 102 pp.; Jiménez & Tinaut, 1992Jiménez, J. & Tinaut A., 1992. Mirmecofauna de la Sierra de Loja (Granada) (Hymenoptera: Formicidae). Orsis, 7: 97-111.; Tinaut et al., 1994, 2007Tinaut, A., Martínez-Ibáñez, M.D. & Ruano, F., 2007. Inventario de las especies de formícidos de Sierra Nevada, Granada (España) (Hymenoptera, Formicidae). Zoologia Baetica, 18: 49-68.; Tinaut, 2016Tinaut. A., 2016. Formícidos del Parque Natural de las sierras de Tejeda, Almijara y Alhama (Andalucía, España) (Hymenoptera, Formicidae). Boletín de la Asociación Española de Entomología, 40 (1-2): 125-159.); Guadalajara (Fernández, 2021Fernández, J.A., 2021. Las hormigas de Tendilla. LaMarabuntaDigital, 6: 24-31.); Huesca (Espadaler, 1979Espadaler, X., 1979. Citas nuevas o interesantes de hormigas (Hym. Formicidae) para España. Boletín de la Asociación Española de Entomología, 3: 95-101.); Jaén (Espadaler, 1997bEspadaler, X., 1997b. Formícidos de las sierras de Cazorla, del Pozo y Segura (Jaén, España) (Hymenoptera, Formicidae). Ecología, 11: 489-499.; Obregón et al., 2014Obregón, R., López, J., & Reyes-López, J.L., 2014. Catálogo de la fauna de hormigas (Hymenoptera, Formicidae) de Sierra Mágina (Jaén, España). Boletín de la Sociedad Entomológica Aragonesa, 54: 370-374.); León (Crespo-Montalbán et al., 2025Crespo-Montalbán, M., Cuesta-Segura, A.D. & García, F., 2025. Las hormigas (Hymenoptera: Formicidae) de Navatejera y lista actualizada para la provincia de León. Boletín de la Sociedad Entomológica Aragonesa, 76: 127-138.); Lleida (García et al., 2009García, F., Espadaler, X. & Gómez, K., 2009. Primera cita de Amblyopone impressifrons (Emery, 1869) para la península ibérica y de Proceratium melinum (Roger, 1860) para Cataluña. (Hymenoptera: Formicidae). Boletín de la Sociedad Entomológica Aragonesa, 45: 357-360.); Madrid (Espadaler & López-Colón, 2011Espadaler, X. & López-Colón, J.I., 2011. Hormigas (Hymenoptera, Formicidae) de una zona de yesos de la Comunidad de Madrid (España). Boletín de la Sociedad entomológica Aragonesa, 49: 261-264.); Murcia (Martínez-Ibáñez et al., 2002Martínez-Ibáñez, M. D., Arnaldos, M.I., Romera, E. & García, M.D., 2002. Los Formicidae (Hymenoptera) de una comunidad sarcosaprófaga en un ecosistema mediterráneo. Anales de Biología, 24: 33-44.; Arcos et al., 2013Arcos, J., Espadaler, X. & Catarineu, C., 2013. Nuevas citas de Temnothorax cristinae (Espadaler, 1997) para el sureste de la península ibérica y ampliación de su descripción. Iberomyrmex, 5: 5-8.; Catarineu et al., 2018Catarineu, C., Barberá, G.G. & Reyes-López, J.L., 2018. Zoogeography of the Ants (Hymenoptera: Formicidae) of the Segura River Basin. Sociobiology, 65: 383-396. https://doi.org/10.13102/sociobiology.v65i3.2822); Tarragona (De Haro & Collingwood, 1981De Haro, A. & Collingwood, C.A., 1981. Formícidos de las Sierras de Prades-Montsant, Sierras de Cavalls-Alfara-Montes Blancos (Tarragona). Boletín de la Estación Central de Ecología, 10: 55-58.) and Zaragoza (Espadaler, 1997cEspadaler, X., 1997c. Hymenoptera 2: Familia Formicidae. Catalogus de la Entomofauna Aragonesa, 13: 13-21.). In the Balearic Islands is known only from Majorca (Espadaler & Cagniant, 1991Espadaler, X. & López-Soria, L., 1991. Rareness of certain Mediterranean ant species: fact or artifact? Insectes Sociaux, 38: 365-377. https://doi.org/10.1007/BF01241872; Gómez, 2004Gómez, K., 2004. Citas nuevas o interesantes de hormigas (Hymenoptera: Formicidae) para la isla de Mallorca (Baleares, España). Boletín de la Sociedad Entomológica Aragonesa, 34: 107-108.; Borowiec et al. 2015Borowiec, L., Galkowski, C. & Salata, S., 2015. What is Tetramorium semilaeve André, 1883? (Hymenoptera, Formicidae). ZooKeys, 512: 39-62. https://doi.org/10.3897/zookeys.512.10006). In Andorra it was recorded by Espadaler et al. (2008)Espadaler, X., Pujade-Villar, J. & Bernadou, A., 2008. Contribució al coneixement de la taxonomia i la fenologia de les formigues (Hymenoptera: Formicidae) d’Andorra. Butlletí de l’Institució Catalana d’Història Natural, 74: 81-90. and in Portugal there are two records close to Lisbon (AIM, 2015AIM. Asociación Ibérica de Mirmecología, 2015. Listado de especies de hormigas encontradas durante el “Taxomara Lisboa 2015”. Iberomyrmex, 7: 44-45.) (Fig. 4).
Figure 4. Map of the known Iberian and Balearic records for Plagiolepis xene (yellow circles are bibliographical; red squares new ones) and P. pygmaea (green circles).
Figura 4. Mapa de las citas ibéricas y baleares conocidas de Plagiolepis xene (los círculos amarillos son bibliográficas; los cuadrados rojos, nuevas) y P. pygmaea (círculos verdes).
The following are new records from Spain sorted by provinces. In all cases the captures were made in P. pygmaea colonies nesting under stones:
BARCELONA: Vinyes de Sabadell, Lavern. 28/IV/2022. 41.399° N, 1.785° E. 220 m.a.s.l. Crops edge. Four gynes. F. García leg. // L’Abella, Sant Martí de Centelles. 24/III/2014. 41.765° N, 2.243° E. 680 m.a.s.l. Mediterranean shrubland. Six gynes. F. García leg. // La Coscollada, Badalona. 29/III/2018. 41.488°N, 2.237° E. 280 m.a.s.l. Mediterranean shrubland. Three gynes. F. García leg. // Monistrol de Monterrat. 26/III/2025. 41.6055° N, 1.8598° E, 290 m.a.s.l. Rosmarinus officinalis L. shrubs, under stone. Plagiolepis grassei was present in the same nest. M. Menchetti & F. García leg. // Les Pinedes de l’Armengol, La Torre de Claramunt. -IV-2026. 41.509° N, 1.620° E. 460 m.a.s.l. Pinus halepensis Mill. forest. F. García leg.
HUESCA: Puerto de Angelé, Castiello de Jaca. 13/V/2025. 42.650° N, 0.573°W. 1140 m.a.s.l. Three gynes. F. García leg.
PALENCIA: Dueñas, “pico de Torilejo”. 29/IV/2024. 41.880° N, 4.624°W. 820 m.a.s.l. Open forest with pastures. Eight gynes. F. García & A.D. Cuesta-Segura leg. // Cevico de la Torre, 28/VI-18/VII/2023, 41.834° N, 4.449°W, 873 m.a.s.l., one alate gyne; 41.836° N, 4.448°W, 869 m.a.s.l., one gyne, grasses and scattered low scrub, with some holm oaks and bare ground. Both gynes where collected in pitfall traps together with P. pygmaea workers. A.D. Cuesta-Segura leg. // Ruesga (Cervera de Pisuerga), 14- 27/ VI/2025, 42.8667° N, 4.5369°W. 1065 m.a.s.l. One gyne in a pitfall trap. C. Prieto, J. Fernández & A.D. Cuesta-Segura leg.
SEGOVIA: Revenga reservoir. 5/V/2018. 40.862° N, 4.091°W. 1180 m.a.s.l. Quercus ilex L. forest edge. There were dozens of gynes in the nest. F. García leg.
TARRAGONA: La Selva del Camp. 4/VII/2012. 41.2188° N, 1.1436° E. 224 m.a.s.l. A dealate gyne in a pitfall trap set in an organic citrus grove. X. Espadaler leg. The presence in the area has been known since 2005.
VALENCIA: Las Fuentes, Ayora. 18/II/2017. 39.068° N, 1.081°W. 670 m.a.s.l. Open Pinus halepensis Mill. forest. There were dozens of gynes in the nest. F. García leg.
The main host species, P. pygmaea, is widely distributed around the Mediterranean Basin (Borowiec & Salata, 2022Borowiec, L. & Salata, S., 2022. A monographic review of ants of Greece (Hymenoptera: Formicidae). Vol. 1. Introduction and review of all subfamilies except the subfamily Myrmicinae. Part 1: text. Natural History Monographs of the Upper Silesian Museum. Bytom. 297 pp.), and is an abundant species in the Mediterranean biogeographic region of Iberia, where it accounts with more than 600 records (Fig. 4), following the database of antmaps.org (Janicki et al., 2016Janicki, J., Narula, N., Ziegler, M., Guénard, B. & Economo, E.P., 2016. Visualizing and interacting with large-volume biodiversity data using client-server web-mapping applications: The design and implementation of antmaps.org. Ecological Informatics, 32: 185-193. https://doi.org/10.1016/j.ecoinf.2016.02.006; Guénard et al., 2017Guénard, B., Weiser, M., Gómez, K., Narula, N. & Economo, E.P., 2017. The Global Ant Biodiversity Informatics (GABI) database: a synthesis of ant species geographic distributions. Myrmecological News, 24: 83-89.).
Until a decade ago, the known Iberian distribution of P. xene was restricted to the eastern part of the peninsula, in areas more or less close to the Mediterranean Sea, while P. pygmaea was found across most of the territory. Since then, new records from Portugal and central Spain (AIM, 2015AIM. Asociación Ibérica de Mirmecología, 2015. Listado de especies de hormigas encontradas durante el “Taxomara Lisboa 2015”. Iberomyrmex, 7: 44-45.; Obregón & Reyes-López, 2015Obregón, R. & Reyes-López, J.L., 2015. Primera aproximación a la mirmecocenosis (Hymenoptera, Formicidae) de Sierra Madrona (Ciudad real, España). Boletín de la Sociedad Entomológica Aragonesa, 56: 191-194.; Crespo-Montalbán et al., 2025Crespo-Montalbán, M., Cuesta-Segura, A.D. & García, F., 2025. Las hormigas (Hymenoptera: Formicidae) de Navatejera y lista actualizada para la provincia de León. Boletín de la Sociedad Entomológica Aragonesa, 76: 127-138.) show that P. xene has a similar distribution to P. pygmaea, suggesting no particular ecological requirements with respect to its host. New samplings in southwestern Iberia could help to clarify this pattern.
Gynes of P. xene are very small (1.2–1.3 mm long), resembling the size of the host workers (1.2–2.4 mm) (Fig. 5) and being much smaller than the host gynes (3.4–4.5 mm) (Kutter, 1952Kutter, H., 1952. Über Plagiolepis xene Stärcke (Hym., Formicid.). Mitteilungen der Schweizerischen Entomologischen Gesellschaft, 25: 57-72.). However, their yellowish coloration (sometimes brownish), and the structure of the mesosoma should allow the identification inside the host nest, even if callow workers of the host were present. Moreover, P. xene gynes have a slower and distinct way of moving than the host workers. Wing development is variable, from fully alate individuals to others with just vestigial wings (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].). In lateral view, metanotum and propodeum are at the same level, making the dorsal profile of the mesosoma relatively flat (Fig. 6). Although similar in size to P. ampeloni (Table 1), P. xene can be distinguished by the presence of four or five mandibular teeth and by the lower eye position (Seifert, 2018Seifert, B., 2018. The Ants of Central and North Europe. Lutra Verlags, Tauer. 408 pp.) (Figs. 1, 6).
Figure 5. Plagiolepis xene gynes from Collserola in a nest of P. pygmaea.
Figura 5. Reinas de Plagiolepis xene de Collserola en un nido de P. pygmaea.
Figure 6. Plagiolepis xene gyne from Collserola: a) mesosoma, lateral view; b) head, frontal view; c) mesosoma, dorsal view; d) detail of the mandibular teeth in three specimens. Scales: 250 µm.
Figura 6. Reina de Plagiolepis xene de Collserola: a) mesosoma, vista lateral; b) cabeza, vista frontal; c) mesosoma, vista dorsal; d) detalle de los dientes mandibulares en tres ejemplares. Escalas: 250 µm.
Males are apterous and closely resemble gynes, differing mainly in the presence of the genitalia and the six gastral tergites (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].). The genitalia are very characteristic, being ventrally projected, with a long and pointed sagitta and the volsella protruding from the stipites margin (Kutter, 1952Kutter, H., 1952. Über Plagiolepis xene Stärcke (Hym., Formicid.). Mitteilungen der Schweizerischen Entomologischen Gesellschaft, 25: 57-72.) (Fig. 7).
The number of P. xene individuals in a colony can oscillate from a few to several dozens (Aron et al., 1999Aron, S., Passera, L. & Keller, L., 1999. Evolution of social parasitism in ants: size of sexuals, sex ratio and mechanisms of caste determination. Proceedings of the Royal Society of London, 266: 173-177. https://doi.org/10.1098/rspb.1999.0618). Even though the species can be considered globally rare, local populations may exhibit high parasitism rates, with 30-50% of host colonies affected (Passera et al., 2001Passera, L., Gilbert, M. & Aron, S., 2001. Social parasitism in ants: effects of the inquiline parasite Plagiolepis xene St. on queen distribution and worker production of its host Plagiolepis pygmaea Latr. Insectes Sociaux, 48: 74-79. https://doi.org/10.1007/PL00001749). This pattern is common in social parasites, which present patchy distribution in those areas with a higher density of host colonies, although generally the proportion of parasitized colonies found in other social parasitic species is much lower, commonly being 1 to 3% (Buschinger, 2009Buschinger, A., 2009. Social parasitism among ants: a review. Myrmecological News, 12: 219-235. https://doi.org/10.25849/myrmecol.news_012:219). Gynes of P. xene are not treated as queens by P. pygmaea workers, and were not observed to be surrounded by aggregations of host workers (Passera, 1969Passera, L., 1969. Interactions et fécondité des reines de Plagiolepis pygmaea Latr. et de ses parasites sociaux P. grassei Le Masne et Passera et P. xene St. (Hym. Formicidae). Insectes Sociaux, 3: 179-194. https://doi.org/10.1007/BF02223409). Plagiolepis xene has an effect on the host societies by reducing the worker production through oophagy (Passera et al., 2001Passera, L., Gilbert, M. & Aron, S., 2001. Social parasitism in ants: effects of the inquiline parasite Plagiolepis xene St. on queen distribution and worker production of its host Plagiolepis pygmaea Latr. Insectes Sociaux, 48: 74-79. https://doi.org/10.1007/PL00001749). Mating is intranidal, and the gynes fly from late June to October (Aron et al., 1999Aron, S., Passera, L. & Keller, L., 1999. Evolution of social parasitism in ants: size of sexuals, sex ratio and mechanisms of caste determination. Proceedings of the Royal Society of London, 266: 173-177. https://doi.org/10.1098/rspb.1999.0618; García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.), as recorded in the captures from the pitfall traps of Cevico de la Torre and Ruesga in this study.
Figure 7. Plagiolepis xene male from Collserola: a) habitus, lateral view; b) head, frontal view; c) mesosoma, dorsal view; d) genitalia, ventral view. Scales: 250 µm.
Figura 7. Macho de P. xene de Collserola: a) hábitus, vista lateral; b) cabeza, vista frontal; c) mesosoma, vista dorsal; d) genitalia, vista ventral. Escalas: 250 µm.
3.3. Plagiolepis grassei (Le Masne, 1956)
Plagiolepis grassei is a species with a restricted distribution known to occur in a few locations in southern France, northern Spain and Sicily (Schifani, 2017Schifani, E., 2017. First record of the vulnerable social parasite ant Plagiolepis grassei in Italy (Hymenoptera: Formicidae). Fragmenta Entomologica, 49: 61-64. https://doi.org/10.4081/fe.2017.231; García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.; Antarea, 2024Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].) (Fig. 8). It is listed as vulnerable by the UICN (Social Insects Specialist Group, 1996bSocial Insects Specialist Group., 1996b. Plagiolepis grassei. The IUCN Red List of Threatened Species 1996: e.T17464A7087398. https://doi.org/10.2305/IUCN.UK.1996.RLTS.T17464A7087398.en). In Spain the species has been recorded in five localities in the provinces of Pontevedra (Espadaler, 1979Espadaler, X., 1979. Citas nuevas o interesantes de hormigas (Hym. Formicidae) para España. Boletín de la Asociación Española de Entomología, 3: 95-101.) and Barcelona (Valcárcel et al., 2010Valcárcel, N., Masó, G., Mederos, J. & Nel.lo, M., 2010. Estudi preliminar dels insectes i altres artròpodes a les codines del Parc Natural de Sant Llorenç del Munt i l’Obac. Xarxa de Parcs Naturals, Diputació de Barcelona, Barcelona. 45 pp.; García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.). Other records from southern Iberia (Reyes-López et al., 2008Reyes-López, J.L., Carpintero, S. & Ordóñez, C., 2008. Nuevos e interesantes datos para los formícidos de Andalucía (Hymenoptera: Formicidae). Subfamilias Ponerinae, Dolichoderinae y Formicinae. Boletín de la Asociación Española de Entomología, 32 (1): 167-171.; Martínez-Ibáñez et al., 2002Martínez-Ibáñez, M. D., Arnaldos, M.I., Romera, E. & García, M.D., 2002. Los Formicidae (Hymenoptera) de una comunidad sarcosaprófaga en un ecosistema mediterráneo. Anales de Biología, 24: 33-44., Catarineu et al., 2018Catarineu, C., Barberá, G.G. & Reyes-López, J.L., 2018. Zoogeography of the Ants (Hymenoptera: Formicidae) of the Segura River Basin. Sociobiology, 65: 383-396. https://doi.org/10.13102/sociobiology.v65i3.2822) may correspond to a closely related, yet undescribed species (García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.).
We add two new records for the species:
BARCELONA: Serra de Cul de Portadora, Monistrol de Montserrat. 26/III/2025, 41.6055° N, 1.8598° E, 290 m.a.s.l. Rosmarinus officinalis L. shrubs, under stone. Ten gynes and 5 workers. Plagiolepis xene was also present in the same nest. M. Menchetti and F. García leg.
TARRAGONA: La Selva del Camp. 4/VII/2012. 41.2188° N, 1.1436° E. 224 m.a.s.l. A dealate gyne in a pitfall trap set in an organic citrus grove. X. Espadaler leg.
Figure 8. Map of the known records for Plagiolepis grassei (yellow circles are bibliographical; red squares new ones) and P. pygmaea (green circles) in the Iberian Peninsula and Balearic Islands. A possible new species recorded in the literature as P. grassei are represented by big green light circles.
Figura 8. Mapa de las citas conocidas de Plagiolepis grassei (círculos amarillos: registros bibliográficos; cuadrados rojos: registros nuevos) y P. pygmaea (círculos verdes) en la península ibérica e Islas Baleares. La posible nueva especie citada en la literatura como P. grassei se representa con círculos verdes claros de mayor tamaño.
In Montjuïc, Barcelona, drowned alates were collected in 2007 between 10/VII and 18/VIII (García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.). In the same mountain, a colony apparently engaging in nest relocation, with alate gynes and a male, was found on 5/VIII/2009. It is worth noting that Montjuïc is surrounded by the urban area of Barcelona and most of its surface is covered by urban parks.
Its host is P. pygmaea (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].). Plagiolepis grassei presents a worker caste (Fig. 9), although in low numbers, having been thought to represent an intermediate stage in social parasitic evolution towards a full inquiline (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].; Passera, 1968Passera, L., 1968. Observations biologiques sur la fourmi Plagiolepis grassei Le Masne Passera parasite social de Plagiolepis pygmaea Latr. (Hym. Formicidae). Insectes Sociaux, 4: 327-336. https://doi.org/10.1007/BF02223631). The best account of colony population was made by Passera (1977)Passera, L., 1977. L’absence d’”effet royal” chez les ouvrières gynécoïdes de la fourmi parasite social Plagiolepis grassei (Hym. Formicidae). Comptes Rendus Hebdomadaires des Séances. Série D Sciences Naturelles, 285: 1447-1449., who found a colony composed of 1500 P. pygmaea workers, 24 P. grassei gynes and 160 P. grassei workers, even though parasite numbers are usually lower (Passera, 1968Passera, L., 1968. Observations biologiques sur la fourmi Plagiolepis grassei Le Masne Passera parasite social de Plagiolepis pygmaea Latr. (Hym. Formicidae). Insectes Sociaux, 4: 327-336. https://doi.org/10.1007/BF02223631). In some cases, P. grassei and P. xene have been found parasitizing the same P. pygmaea nests (Schifani, 2017Schifani, E., 2017. First record of the vulnerable social parasite ant Plagiolepis grassei in Italy (Hymenoptera: Formicidae). Fragmenta Entomologica, 49: 61-64. https://doi.org/10.4081/fe.2017.231; García et al., 2020García, F., Espadaler, X., Roig, X., Serrano, S. & Cuesta-Segura, A.D., 2020. Vuelos nupciales en hormigas: estudio de los sexuados ahogados en cuatro masas de agua ibéricas (Hymenoptera: Formicidae). Sociedad Entomológica Aragonesa. 40 años sin Félix: homenaje al Dr. Rodríguez de la Fuente: 255-268.; this work).
Worker caste cannot maintain the gynes alive without the presence of P. pygmaea workers (Passera, 1968Passera, L., 1968. Observations biologiques sur la fourmi Plagiolepis grassei Le Masne Passera parasite social de Plagiolepis pygmaea Latr. (Hym. Formicidae). Insectes Sociaux, 4: 327-336. https://doi.org/10.1007/BF02223631). The gynes are treated in a similar way as the host’s gynes, with groups of workers being observed surrounding them (Passera, 1969Passera, L., 1969. Interactions et fécondité des reines de Plagiolepis pygmaea Latr. et de ses parasites sociaux P. grassei Le Masne et Passera et P. xene St. (Hym. Formicidae). Insectes Sociaux, 3: 179-194. https://doi.org/10.1007/BF02223409) (Fig. 9b). Although the sex ratio is balanced and nuptial flights have been observed, adelphogamy (i.e., mating between sexuates from the same colony) has been suggested (Passera, 1968Passera, L., 1968. Observations biologiques sur la fourmi Plagiolepis grassei Le Masne Passera parasite social de Plagiolepis pygmaea Latr. (Hym. Formicidae). Insectes Sociaux, 4: 327-336. https://doi.org/10.1007/BF02223631). Sexuates emerge from hibernated larvae, while workers develop later from eggs laid in the same year (Passera, 1968Passera, L., 1968. Observations biologiques sur la fourmi Plagiolepis grassei Le Masne Passera parasite social de Plagiolepis pygmaea Latr. (Hym. Formicidae). Insectes Sociaux, 4: 327-336. https://doi.org/10.1007/BF02223631).
Figure 9. Plagiolepis grassei from Monistrol de Montserrat, in a nest of P. pygmaea. a) three gynes (centre) between host workers; b) gyne with host workers around.
Figura 9. Plagiolepis grassei de Monistrol de Montserrat, en un nido de P. pygmaea. a) tres reinas (centro) entre obreras hospedadoras; b) reina con obreras hospedadoras alrededor.
There are few images concerning this species, and for some castes the only information available is the short verbal diagnosis given by Le Masne (1956)Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024]., since the formal morphological description announced there was never published. Therefore, we present pictures of all castes, biometry and a more precise diagnosis of them.
4. WORKER
Workers are yellowish and have a total length of 1.7-1.9 mm (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].), being smaller than average P. pygmaea workers (Passera, 1968Passera, L., 1968. Observations biologiques sur la fourmi Plagiolepis grassei Le Masne Passera parasite social de Plagiolepis pygmaea Latr. (Hym. Formicidae). Insectes Sociaux, 4: 327-336. https://doi.org/10.1007/BF02223631), without almost any observed overlap in the studied sample (Table 1). The ocelli are always present (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].) (Fig. 10). However, they are somewhat lightly coloured, and preserved specimens appear to lose the pigmentation over time. The antennal structure resembles that of P. pygmaea, with the 3rd and 4th segments shorter than the 5th (Fig. 10).
Figure 10. Plagiolepis grassei worker from Monistrol de Montserrat: a) head, frontal view; b) detail of the funicle. Scale: 250 µm.
Figura 10. Obrera de Plagiolepis grassei de Monistrol de Montserrat: a) cabeza, vista frontal; b) detalle del funículo. Escala: 250 µm.
The mesosoma is distinctly gynecoid, with a more developed mesonotum that makes the suture with the pronotum more sinuose in lateral view (Fig. 11). The degree of mesonotal development is variable. In dorsal view, the mesonotum can be asymmetric and presents different degrees of development regarding its posterolateral margins, ranging from having vestigial wings (Passera, 1977Passera, L., 1977. L’absence d’”effet royal” chez les ouvrières gynécoïdes de la fourmi parasite social Plagiolepis grassei (Hym. Formicidae). Comptes Rendus Hebdomadaires des Séances. Série D Sciences Naturelles, 285: 1447-1449.) to two scar-like perforations or invaginations (Fig. 11). In some specimens, a trace of scutellum can be found. Pronotum and mesonotum bear erect or suberect pilosity (Fig. 11), while in P. pygmaea there is only appressed pubescence.
Plagiolepis grassei workers can be confused with small callow workers of P. pygmaea, but the latter are generally more whitish.
Figure 11. Mesosoma of Plagiolepis grassei workers from Collserola (a-c) and from Monistrol de Montserrat (d). a) lateral view; b, d) dorsal view; c) dorsolateral view. Note the lower degree of development of the sockets on the base of mesonotum in d. Scale: 250 µm.
Figura 11. Mesosoma de obreras de Plagiolepis grassei de Collserola (a-c) y de Monistrol de Montserrat (d): a) vista lateral; b, d) vista dorsal; c) vista dorsolateral. Obsérvese el menor grado de desarrollo de las cavidades en la base del mesonoto en d. Escalas: 250 µm.
5. GYNE
This caste has a yellowish coloration and a total length of 2–2.4 mm (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].), showing no size overlap with the smaller P. xene (Table 1). Antennal structure is similar to that of P. pygmaea, with the 3rd and 4th segments shorter than the 5th. Mandibles with 4 or 5 teeth (Fig. 12).
Figure 12. Plagiolepis grassei gyne from the Garraf Massif: a) mesosoma and petiole, dorsal view; b) head, frontal view; c) mesosoma and petiole, lateral view; d) mandibular teeth. Scales: 250 µm.
Figura 12. Reina de Plagiolepis grassei del macizo del Garraf: a) mesosoma y pecíolo, vista dorsal; b) cabeza, vista frontal; c) mesosoma y peciolo, vista lateral; d) dientes mandibulares. Escalas: 250 µm.
In lateral view of the mesosoma, the metanotum is usually at a higher position than the propodeum, while in P. xene it is almost always at the same level (Figs. 6, 12). Pilosity is more profuse on head and mesosoma (Figs. 6, 12).
6. MALE
In the male, the most diagnostic characters are found in the head, which is longer than wide (Table 1), and with smaller and less protruding eyes with respect to free-living Plagiolepis males (Fig. 13). The antennae are 11–segmented as in female castes, while in P. pygmaea is 12–segmented (Le Masne, 1956Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024].). Funicle with structure similar to that of the female castes. Mandibles with four teeth. Coloration is yellowish brown. Size is similar to or slightly smaller than, that of average P. pygmaea males. Mesosoma sclerites structure is mostly similar to those in P. pygmaea males, except for a less developed pronotum (Fig. 13). Even though Le Masne (1956)Antarea, 2024. Plagiolepis grassei Le Masne, 1956 FORMICINAE. Available from https://antarea.fr/fourmi/?repartition/repertition-especes.html?espece=243 [accessed 6 Oct. 2024]. mentions an imperfect wing development, the poor state of conservation of the wings in the single male available prevented a reliable assessment. The genitalia are directed downwards, similarly to P. xene, but without the sagitta and volsella projecting from stipites (Fig. 13).
Figure 13. Plagiolepis grassei male from Montjuïc: a) mesosoma and petiole, lateral view; b) head, frontal view; c) genitalia, ventral view; d) genitalia, lateral view. Scales: 250 µm.
Figura 13. Macho de P. grassei de Montjuïc: a) mesosoma y peciolo, vista lateral; b) cabeza, vista frontal; c) genitalia, vista ventral; d) genitalia, vista lateral. Escalas: 250 µm.
Supplementary information ↑
Funding sources
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Supplementary material
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Data availability
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Acknowledgements
Carlos Prieto and Jon Fernández Pérez (together with the second author) set and separated the pitfall traps in Ruesga (Palencia), which were collected by all attendees at the XXIV Iberian Arachnology Conference. The captures made in Castilla y León were carried out under the mandatory capture permits. To Mattia Menchetti, who found the colony of P. grassei in Monistrol de Montserrat. To Roberto Poggi, from the Natural History Museum (Genova, Italy) for lending type material of Plagiolepis pygmaea var. pyrenaica Emery. The two anonymous reviewers improved and clarified the manuscript.
Authorship contribution statement
Fede García: Conceptualization, Formal Analysis, Research, Methodology, Project Management, Writing – original draft, Writing – revision, and editing.
Amonio David Cuesta-Segura: Formal Analysis, Research, Methodology, Writing – revision, and editing.
Xavier Espadaler: Research, Methodology, Writing – revision, and editing.
Competing interests
The authors declare that there are no conflicts of interest related to this research.
Statement on the use of Artificial Intelligence
Not applicable.
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