Loxa deducta Walker, 1867 (Heteroptera: Pentatomidae) en Chile: distribución, historia de invasión e identificación

The presence of the introduced stink bug Loxa deducta Walker, 1867 in Chile is analyzed. New records are provided for the Valparaíso, O ́Higgins and Maule regions, extending its distribution southwards and northwards. Identification tips are provided to differentiate it from other Chilean pentatomids, as well as Loxa Amyot & Serville, 1843 species in the neighbor countries.

Loxa Amyot & Serville, 1843 is a new world genus of Pentatomidae currently classified within the Pentatominae and the recently erected tribe Chlorocorini (Rider et al., 2018).
Loxa deducta Walker, 1867 is a Neotropical pentatomid species widely distributed in Central and South America (Eger, 1978). Loxa deducta is considered an economically important species as it attacks soybean and citric crops (Schaefer & Panizzi, 2000). This species has been found in Chile since 2005 (Mondaca et al., 2008); being the only South American country in which L. deducta is considered introduced (Faúndez & Carvajal, 2011). Although this species has entered in the country long time ago, there is no further information about its presence in the country, establishment and updated distribution. In addition, no identification notes are available to tell apart L. deducta from some Chilean species. The purpose of this work is to analyze the current situation of L. deducta in Chile, as well as provide identification tools to tell it apart from Chilean and close related species around the country.
The distribution and expansion of this species in Chile was surveyed continuously by the authors since it was reported in the country. Surveys included collecting, prospection and records coming from identifications made for public institutions, private companies and citizen science through the facebook site "Insectos de Chile -oficial" (https://www.facebook.com/groups/777914522238618/?ref=br_rs). In addition, national and international collections were revised in searching of specimens, as well as records in the literature. For systematics we follow Rider et al. (2018) and morphology and identification to Eger (1978).
Material examined is deposited in the collection of Instituto de la Patagonia, Universidad de Magallanes. identification. Through the years, L. deducta (Figs. 1,9,10) has been confused mainly with three, species the Asopine bug Brontocoris nigrolimbatus (Spinola, 1852) (Figs. 2, 5) and the Pentatomines Thyanta rubicunda Rider, 1991 andThyanta perditor (Fabricius, 1794) (Figs. 3, 6). From B. nigrolimbatus it can be easily differentiated by the shape of the head, which is truncate in B. nigrolimbatus whereas it is subtriangular in L. deducta. Additionally the projections of the humeral angles of the pronotum are more developed in L. deducta, as well as the serrate anterolateral margins (Figs. 4,5). From both T. rubicunda and T. perditor by the shape of paraclypei, with rounded apex in Thyanta species and pointed apex in L. deducta. Also by the shape of pronotum, with humeral angle projections and anterolateral margins dentations tiny in Thyanta, whereas those are strong in L. deducta (Figs. 4,6).
Although L. deducta is the only species of Loxa present in Chile there are several species in Peru, Argentina and Bolivia. Few times we have observed isolated specimens of L. virescens Amyot & Serville, 1843, coming in goods from Argentina. Therefore, it is important to remark how to separate L. deducta from geographically close species that may enter occasionally to the country. From the Peruvian species L. peruviensis Eger, 1978, it can be easily differentiated by the more produced humeral angle projections (Figs. 4-8). From L. melanita Eger, 1978 andL. parapallida Eger, 1978 it can be differentiated by the less developed eyes (Figs. 4-7 the divergent first gonocoxae of females and the U shaped median invagination of male pygophore (Figs. 11, 14). From L. virescens and L. viridis (Palisot de Beauvois, 1811), present in Argentina there are several overlaps within the variability of general body features of the three species. Thus genitalia examination is essential to get a correct identification. Loxa deducta can be recognized by the very divergent first gonocoxae of female (Figs. 14-16), and by the deepest U-shaped invagination of the pygophore in ventral view. Additionally the lateroventral margins of the pygophore are pointed in L. deducta and more truncated in L. virescens and L. viridis (Figs. 11-13). distribution and bionoMics. Mondaca et al. (2008) reported this species from a few localities in Santiago (Metropolitan Region). Later, Faúndez & Carvajal (2011) did not include any additional new data on this species. By our field observations, it seems that this species was in an adaptation period from 2005 to 2010, where the collection or sightings were just sporadic. However, after that period the Figs. 4-10.-Head andpronotum. 4. Loxa deducta Walker, 1867. 5. Brontocoris nigrolimbatus (Spinola, 1852). 6. Thyanta perditor (Fabricius, 1794). 7. Loxa melanita Eger, 1978. 8. Loxa peruviensis Eger, 1978 sightings and collections become more frequent in urban areas of Metropolitan Region, even founding them ovipositing at homes. The oviposition in homes (mostly in the walls and curtains) has been detected frequently especially since 2013. These egg batches included from 12-25 eggs. Up to 2016 it has been found in the following localities within the Metropolitan Region: Santiago Centro, Buin, Conchalí, Ñuñoa, Maipú, Recoleta, Providencia, El Bosque, Quilicura, San Joaquín, Chicureo, Pedro Aguirre Cerda, La Pintana, Pudahuel, San Miguel. Besides of these urban or periurban environments, in 2017 it has been found in Cajón del Maipo, and Cuesta Zapata. Finally in the last years, we found the first specimens of this species outside the Metropolitan Region, extending it distribution to the Valparaíso Region in the North and to the Maule Region in the south (Fig. 17).
Loxa deducta has become well adapted to the country and one of the most common species in the Metropolitan Region. However instead of being an agricultural pest, Chile it seems to show more synanthropic or hemisynanthropic habits. After more than 10 years it just recently started to spread across the country; reching the regions of Valparaíso, O´Higgins and Maule. These expansions also coincides with the arrival to Chile (more specifically Metropolitan Region) of the invasive stink bug species Halyomorpha halys (Stål, 1855) (Faúndez & Rider, 2017), and Bagrada hilaris (Burmeister, 1835) (Faúndez et al., 2016Faúndez, 2018). Therefore L. deducta is now competing with the above mentioned species for the resources. This situation may have triggered the movement of L. deducta in search of additional food sources.
The presence of this species in homes does not represent a real problem, it usually does not aggregate and there is no record of adventitious bites, or occupational allergies. Thus the overall impact of this species in Chile can be considered low to moderate. It is necessary to take a close look at the recent expansions of this species in Chile, as it may become acting as a pest in other regions with different climate variables and crops availability.