FIRST RECORD OF MENGENILLIDAE (INSECTA, STREPSIPTERA) FROM THE BALEARIC ISLANDS

Ricardo del Río^*, Carlos Barceló^*, Miguel Ángel Miranda^* & Hans Pohl^** 

^*Laboratory of Zoology, University of the Balearic Islands, Cra. Valldemossa Km 7.5, Spain

^**Entomology Group, Institut für Spezielle Zoologie and Evolutionsbiologie, Friedrich-Schiller-Universität Jena, Erbertstraße 1, 07743 Jena, Germany

Corresponding authors: Ricardo del Río and Hans Pohl (e-mail: hans.pohl@uni-jena.de)

IntroductionTOP

Strepsipterans are a monophyletic group of endopterygote insects (Pohl & Beutel, 2005) also known as twisted-wing parasites (from Greek; streptos = twisted and pteron = wings) due to the fact that the forewings in dried specimens are often twisted. To date, approximately 600 species have been described. All species within this group are obligate endoparasites of insects and, except in Mengenillidae, only the first instar larvae (host-seeking stage) and the adult males (which live just long enough to seek and fertilize a female (Kinzelbach, 1978) are free-living. Females remain inside their pterygote hosts throughout their lives, only extruding the cephalothorax to copulate with the male. Strepsipterans are rarely encountered in the field due to the tiny size of the first instar larvae (average total length 230 μm (Pohl, 2002) and the short lifespan of the adult males. The best way to find them in the field is to look for stylopised hosts. Adult males have sometimes been found in Malaise (Pohl & Melber, 1996; Van Zuijlen et al., 1996) or light traps (Henderickx, 1982; Smit & Ramel, 2009; Pohl et al., 2012).

Males and females of this order exhibit an extreme form of sexual dimorphism (Pohl & Beutel, 2005, 2008). Hosts include apterygote insects, Polyneoptera, Hemiptera, and seven orders (34 families) of holometabolous hexapods, namely Zygentoma, Blattodea, Mantodea, Orthoptera, Hemiptera, Diptera and aculeate Hymenoptera (Kathirithamby, 2009). Parasitization occurs when the host is in the larval, nymphal or egg stage (Linsley & MacSwain, 1957; Maeta et al., 2001; Hughes et al., 2003) and continues into host maturity until the male strepsipteran hatches or the first instar larvae of the viviparous female are released to coincide with production of the next generation of the host’s larvae/nymphs/eggs. The lifespan of the host can be lengthened to allow completion of the parasite cycle, though its reproductive capacity is reduced by the castration caused by the parasite (Salt, 1927; Brandenburg, 1956; Strambi & Strambi, 1973; Kathirithamby, 1989; Solulu et al., 1998; Maeta & Kurihara, 1999) and death eventually occurs a few hours or days after the emergence of the adult male or the larvae.

The most basal extant group of Strepsiptera is the recently described Bahiaxenidae (Bravo et al., 2009). The Mengenillidae represent the second branch and form the sister taxon to the remaining Strepsiptera, a group known as Stylopidia (Kinzelbach, 1978, 1990). Mengenillidae parasitize Zygentoma (Lepismatidae), and in contrast to the other strepsipteran species, both male and female larvae emerge to pupate externally and are free-living as adults (Silvestri, 1943; Pohl & Beutel, 2008).

There is only one valid species in the genus Eoxenos. Eoxenos laboulbenei has been recorded from Algeria, the Canary Islands and the Iberian Peninsula, France, Italy including Sardinia and Sicily, Libya and Greece (Kinzelbach, 1978; Smit & Ramel, 2009). The known hosts are Tricholepsima aurea (Dufour), Neoasterolepisma crassipes (Escherich), N. wasmanni (Moniez) and N. pallida Molero, Gaju and Bach (Zygentoma) (Silvestri, 1941a; Delgado et al., 2014). The genus Mengenilla is restricted to Palearctic, Afrotropical, Australian and Oriental regions (Cook, 2007; Pohl et al., 2012). Mengenilla chobauti Hofeneder, 1910 and M. parvula Silvestri, 1941 occur in the Mediterranean region. Mengenilla chobauti has been recorded from North Africa, Spain, Portugal, Crete, Malta and Italy including Sicily and Sardinia and has the widest distribution of all described Mengenilla species (Silvestri, 1941b, 1943; Kinzelbach, 1978). Mengenilla parvula is found only in Sicily. The known hosts of Mengenilla are Ctenolepisma ciliata (Dufour) (M. chobauti) and C michaelseni Escherich (M. parvula) (Zygentoma) (Silvestri, 1941b).

In this contribution we report the species Eoxenos laboulbenei de Peyerimhoff, 1919 and evidence of the genus Mengenilla (Strepsiptera, Mengenillidae) for the first time in the Balearic Islands.

Material and methodsTOP

Examinations were carried out using a Zeiss stereomicroscope (SteReo Discovery .V8) and a Leica MZ 12.5. For micro photography, one specimen of E. laboulbenei was dehydrated using increasing steps of ethanol up to 100% and dried at the critical point (Emitech K850 critical point dryer). Photographs of E. laboulbenei and the puparium of Mengenilla sp. were taken with a Nikon D 90 digital SLR equipped with a 25 mm and a 63 mm Zeiss Luminar macro lense, plus an adjustable extension bellows. The specimens were illuminated by two flashlights fitted with a transparent cylinder for soft and even light. Zerene Stacker Version 1.04 was used to combine a stack of several partially focused images.

The information pertaining to the specimens is given in the standard manner, i.e., locality, geographic coordinates, date of collection (month indicated in lower case Roman numerals), habitat information, collector, and preparation information. Male (♂) and female (♀) symbols indicate the sex. All specimens are deposited in the private collection of Hans Pohl, Jena, Germany.

Adult males of E. laboulbenei were collected using UV light suction traps (Onderstepoort model; ARC-OVI, South Africa). Two UV light traps were operated with 12V batteries from dusk till dawn (8:00 pm to 6:00 am) on several non-consecutive nights. Trapped insects were collected the morning after sampling and taken to the laboratory for examination. The puparia of Mengenilla sp. were collected by turning stones.

ResultsTOP

MATERIAL EXAMINED. Eoxenos laboulbenei. Spain, Balearic islands, Majorca, Felanitx, cattle farm Ca’s Boter, 20 ♂♂, 39°30’N, 03°07’ E, x. 2012, black light, leg. R. del Río & C. Barceló (19 ♂♂ in ethanol, 1 ♂ critical point dried).

Mengenilla sp. Spain, Balearic islands, Ibiza, Forn Nou des Raco, route between Can Pep des Cocons and Can Miquelet, 6 ♂♂ puparia, 7 ♀♀ puparia, 1 badly preserved puparium, sex unknown, 39°00’40’’N, 01°24’10’’E, 01-2.iv.2003, beneath stones (1 ♂ puparium, 3 ♀♀ puparia dry preparation; 5 ♂♂ puparia, 4 ♀♀ puparia in ethanol).

TAXONOMY

The males of Eoxenos laboulbenei (Fig. 1) were distinguished from other strepsipteran species on the basis of the following combination of characters (Kinzelbach, 1971, 1978; Pohl & Beutel, 2005): Compound eyes with 35-45 ommatidia, six-segmented antennae with flabella on antennomeres 3 and 4, robust mandibles with a straight basal part, and five-segmented tarsi with well developed claws.

A generic feature of female Mengenilla puparia (Fig. 2) is a distinct broadening in the anterior region of the metathorax by an angle of approx. 45 degrees. In contrast, the anterior region of the metathorax in female Eoxenos puparia widens at an angle of nearly 90 degrees (pers. observations HP).

The coloration, number of ommatidia, proportions of the antenommeres, shape of the mandibles, and wing venation clearly confirm that the strepsipteran males from Majorca belong to E. laboulbenei.

The puparia from Ibiza were assigned to the genus Mengenilla. However, they differ distinctly from the Mengenilla puparia described to date. The female puparia from Ibiza display, in addition to the broadening in the metathorax, a broadening in the mesothorax (Figs. 2B, 2C). All three pairs of legs of both the male and female puparia insert much more medially on the ventral side of the puparia (Fig. 2C) than in the previously described Mengenilla puparia (M. chobauti, M. parvula, and M. moldrzyki [Silvestri, 1941b, 1943; Pohl et al., 2012]) (Fig. 2F). As a result we cannot yet rule out the possibility that this species is only a variation of M. chobauti. Until adult specimens are available, we hesitate to describe this species as new to science.

AcknowledgementsTOP

Jerry Cook made valuable suggestions which helped to improve the article. Lucy Cathrow improved the English. This is gratefully acknowledged.

ReferencesTOP