Sofía Copperi

Mygalomorph Spider Community of a Natural Reserve in a Hilly System in Central Argentina

Abstract The diversity, abundance, spatial distribution, and phenology of the mygalomorph spider community in the “Ernesto Tornquist” Strict Nature Reserve were analyzed in this study. Located in southwestern Buenos Aires, Argentina, the Reserve is representative of the Ventania system, which is a sigmoidal mountain belt 180 km in length. This exceptional hilly ecosystem is home for many endemic species and rich native fauna and flora. Spider abundance was sampled monthly from October 2009 to October 2010 by hand capture and pitfall traps on grassland slopes. The species recorded in the study area were: Actinopus sp.1 (Actinopodidae); Grammostola vachoni and Plesiopelma longisternale (Theraphosidae); Acanthogonatus centralis (Nemesiidae); and Mecicobothrium thorelli (Mecicobothriidae). Grammostola vachoni and Acanthogonatus centralis were the dominant species in hand capture and pitfall traps, respectively. The seasonal variation, diversity, and abundance of the mygalomorph community are analyzed and discussed here. The Mygalomorphae of the Ventania system comprises an important group of sedentary and cryptozoic spiders that seem to be highly dependent on habitat type and environmental factors.

Aerial dispersal by Actinopus spiderlings (Araneae: Actinopodidae)

Abstract Ballooning, a form of dispersal rarely seen in mygalomorph spiders, was observed in 13 individuals of an undetermined species of Actinopus under laboratory conditions. After ascending a stick, each spiderling initiated ballooning from either the horizontal lines between sticks or from the sticks edges. They became airborne by dropping and dangling from a dragline, which then gradually lifted and lengthened to 10–15 cm in the breeze, broke at its attachment point, and served as a ballooning thread. This method of ballooning has also been observed in araneomorphs and other species of mygalomorphs, and this is probably a more primitive and shorter distance form of ballooning than that typically practiced by higher araneomorphs, which produce airborne silk lines that are pulled from the spider by air currents and are used either as spanning lines or as balloon lines that allow the spider itself to become airborne.

Sexual Behaviour of Mygalomorph Spiders: when Simplicity Becomes Complex; an Update of the Last 21 Years

Summary A generally common impression seems to be that the mygalomorphs have simple repertoires of behaviours, but many authors have concluded that this traditional portrayal of mygalomorph behaviours is misleading. An increasing number of studies of reproductive behaviour of mygalomorphs have revealed intricate and complex mechanisms of communication employed by this group. Our objective was to provide a synthetic treatment of the literature published in the last 21 years about sexual behaviour of mygalomorph spiders, in order to contribute in improving our understanding on the widespread and unique behaviours they exhibit. We provide a brief introduction to reproductive behaviour of mygalomorph spiders, and then examine some of the general patterns of courtship and mating behaviours known on some mygalomorph families.

Copulatory behavior of Microstigmatidae (Araneae: Mygalomorphae): a study with Xenonemesia platensis from Argentina

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.

Another migid in the wall: natural history of the endemic and rare spider Calathotarsus simoni (Mygalomorphae: Migidae) from a hill slope in central Argentina

A population of Calathotarsus simoni Schiapelli and Gerschman (1975) was discovered on a hillside in the Ventania system, Argentina. Our objectives were to quantify burrow density, record burrow morphology and door characteristics and describe the micro-habitat. We counted 57 burrows and report a density of 0.01 burrows/m2. Aggregation indices suggest that burrows are aggregated under some area plots but more evenly distributed on others. The trapdoor is thick and rigid with bevelled edges connected to the entrance rim by a narrow articulated hinge. Two egg sacs from females were obtained and data on eggs and spiderlings are presented. We registered six burrows of an undetermined species of Actinopus. While a few specimens of Actinopus sp. were found inhabiting this hillside, the highest proportion of burrows belonged to C. simoni. Spider diversity on the hillside shows the predominance of Linyphiidae, Nemesiidae and Gnaphosidae. One juvenile of C. simoni was captured using pitfall traps.

The diet of the black widow spider Latrodectus mirabilis (Theridiidae), in two cereal crops of central Argentina

The spider Latrodectus mirabilis (Holmberg, 1876) is commonly found in cereals crops of central Argentina. We studied its diet composition at the field and capture rate on leaf-cutting ants based on laboratory experiments. This study comprises the first approach that documents the diet of L. mirabilis in wheat and oat fields of central Argentina. We identified 1,004 prey items collected from its webs during the last phenological stages of both cereal crops. The prey composition was variable but the spiders prey mainly on ants (Formicidae, Hymenoptera), who represented more than 86% of the total. Meanwhile, in the capture rate experiences we registered a high proportion of ants captured by spiders at the beginning of experiences, capturing the half of the ants from total in the first four hours. Summarizing, we reported a polyphagous diet of this spider species in wheat and oat fields. Ants were the most important prey item of this spider, as found in other Latrodectus spiders around the world.

Sexual Selection in Neotropical Spiders: Examples from Selected Groups

Spiders have long been noted as classic examples of sexual behavior among arachnids, including extreme sexual dimorphism in some groups, and behavioral adaptations to diverse mating patterns. In recent decades, studies on the biology of Neotropical spiders have offered novel information on processes related to reproductive biology, including sexual selection. The present chapter synthesizes the large amount of knowledge on sexual selection and associated subjects in spiders from the Neotropics. Some of the groups considered in this review are mygalomorphs, lycosids and related, orb-weaving species, tetragnathids, social species, pholcids, and oonopids, among others. Concepts, patterns, mechanisms, and prospects on different areas of sexual selection are shown in detail for all these groups. In particular, here we highlight selected examples of the different contexts in which male–female interactions occur, such as mate choice, sexual cannibalism, sperm competition, and cryptic female choice. We outline the potential evolutionary consequences according to those contexts, with a final selection of model groups for specific experimental and comparative investigations.