Primera cita de Mengenillidae (Insecta, Strepsiptera) en las Islas Baleares ; First record of Mengenillidae (Insecta, Strepsiptera) from the Balearic Islands

This is the first report of the strepsipteran species Eoxenos laboulbenei De Peyerimhoff, 1919 and Mengenilla sp. Hofeneder, 1910 on the Balearic Islands. Several males of E. laboulbenei were found in samples obtained using a UV light suction trap on a cattle farm in Majorca in October 2012. A number of empty male and female puparia of Mengenilla sp. were found in Ibiza in April 2003.


Introduction
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(Kinzelbach, , 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).
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 methods
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.
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[Silvestri, , 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.