SHORT COMMUNICATION Copulatory behavior of Microstigmatidae (Araneae: Mygalomorphae): a study with Xenonemesia platensis from Argentina Nelson Ferretti 1 , Gabriel Pompozzi 2 , Sofı ´a Copperi 2 , Fernando Pe ´rez-Miles 3 , and Alda Gonza ´lez 1 : 1 Centro de Estudios Parasitolo ´ gicos y de Vectores CEPAVE (CCT- CONICET- La Plata) (UNLP), La Plata, Argentina. E-mail: nferretti@conicet.gov.ar; 2 Departamento de Biologı ´a, Bioquı ´mica y Farmacia, Universidad Nacional Del Sur, Bahı ´a Blanca, Argentina; 3 Facultad de Ciencias, Seccio ´ n Entomologı ´a, Montevideo, Uruguay Abstract. Microstigmatidae are small ground-dwelling and free-living spiders. The present study reports on the copulatory behavior of Xenonemesia platensis Goloboff 1989, constituting the first report on sexual behavior of the Microstigmatidae. Our findings in X. platensis did not show evidence of pheromones associated with silk. The courtship behavioral units of males was comprised of quivers by legs I and II, brusque movements of the palps, and leg tapping with legs II. During mating, a novel courtship behavior by males was observed that consisted of tapping and scraping with legs II on the female legs. The present study not only gives a description of mating behavior in Microstigmatidae for the first time, but also reports strong evidence of nongenital copulatory courtship activity in mygalomorph spiders. Keywords: Argentinean spider, South America, courtship, mating, reproductive biology Many spider species could be compelling targets for evolutionary studies due to their unusual reproductive biology (Eberhard 2004); it appears that a species of microstigmatids provides just such a target. Microstigmatidae are small ground-dwelling and free-living spiders (Griswold 1985) restricted to habitats offering constant high humidity and even temperature (Lawrence 1953). This family comprises 15 species, nine of them distributed in the New World (Platnick 2011). Members of this family are characterized by rounded book-lung openings and extremely shortened posterior lateral spinnerets (Goloboff 1995). Microstigmatid species, in particular, have long been overlooked, both because of their rarity in collections and their extremely small size (adult males are 1–3 mm in total length) (Raven & Platnick 1981). The spiders are not known to construct burrows or retreats and are supposed to make minimal use of silk. They readily attack and feed upon small insects (Griswold 1985). There are few published records of either the natural history or the ecology of microstigmatid species (Griswold 1985; Dippenaar-Schoeman et al. 2006: Old World species; Indicatti et al. 2008: Brazilian species; Ferretti et al. 2010: Argentinean and Uruguayan species). Here we report on the copulatory behavior of Xenonemesia platensis Goloboff 1989, constituting the first report on sexual behavior of a microstigmatid. We collected three adult males and three adult females at Martı ´n Garcı ´a Island, Buenos Aires, Argentina (34u119250S, 58u159380W), in August 2009. Voucher specimens are still alive and will be deposited in the Museo de La Plata, Division Entomologı ´a, La Plata, Buenos Aires, Argentina. All the females molted before we made observations, so they did not have stored sperm. In the laboratory we kept them individually in plastic Petri dishes (9 cm diameter 3 1.5 cm high), with soil as substrate and wet cotton wool moistened daily. These containers allowed us to follow their behavior as they constructed their burrows. We fed all individuals weekly with cockroaches (Blattella germanica) of approx- imately 10 mm length. We used a 12 h light/dark cycle, and the room temperature during breeding and observations was 26.7uC 6 1.52 SD. In order to observe mating, we placed each female dish inside a larger glass cylindrical container (19 cm diameter and 10 cm high) with a layer of soil approximately 6 cm deep. A depression excavated in the center of the larger container for the female’s Petri dish avoided the destruction of the female’s shelter during the transfer. The mating arena was illuminated with artificial fluorescent light. For each encounter, we removed the male from his Petri dish and carefully introduced him into the larger container housing the female’s dish, and at quite a distance from the female. We performed nine male-female pairings of X. platensis in all combinations, and both males and females were given three possible mating opportunities. We considered only the first pairing for des- cription of behavioral units during courtship and mating sequences because female behavior in particular may change after a first suc- cessful insemination, and since these spiders are very rare, they probably never encounter potential mates at such high frequencies. We recorded copulations with a Handycam Panasonic SDR-S7 and analyzed the video records with a PC program (Sony Vegas 9.0) in order to describe behavioral patterns accurately. We used slow motion and single frame advance modes. Durations and frequencies are given as averages 6 standard deviations. We present the frequency and duration of behavioral units during the three mating exposures and five copulations in Table 1. When X. platensis engaged in courtship and mated, a common pattern occurred (Fig. 1a). All males began the courtship when they directly contacted the female’s body. During this initial contact, females remained largely motionless. The male did not start courtship when he contacted female silk, but did so only after contacting the female herself. Early studies proposed that mygalomorph spiders lacked chemical cues in sexual communication (Baerg 1958; Platnick 1971). However, more recent studies have reported the presence of phero- mones associated with female silk threads (Costa & Pe ´rez-Miles 2002; Ferretti & Ferrero 2008). Our findings in X. platensis could indicate the absence of pheromones associated with silk, but obviously more detailed studies are needed to confirm this. After initial contact, the male quivered with the first and second pair of legs, followed by fast upward and downward movement of the pedipalps. The male made nine behavioral bouts with an average duration of 0.52s 6 0.06 SD (range 5 0.4420.60). At first glance, the quivers observed in the courtship of X. platensis could be similar to the body vibrations observed in some theraphosids (Costa & Pe ´rez- Miles 2002; Ferretti & Ferrero 2008), but in X. platensis the quiver is generated by the first and second pair of legs instead of pair III as observed in theraphosids. After approximately 46 s, the female raised her body up to an angle of almost 60u relative to the substrate, with the first pair of legs elevated and legs III and IV over the substrate. At 2012. The Journal of Arachnology 40:252–255 252