Bioacoustics of Anelosimus monskenyensis

Description Male ( holotype ): Total length 1.80. Prosoma 0.90 long, 0.75 wide, light brown, center and narrow rim darker. Sternum 0.60 long, 0.50 wide, light brown. Opisthosoma 0.95 long, 0.80 wide. Pattern as in other Anelosimus , dark notched dorsal folium, edged by white. Eyes subequal in size about 0.07 in diameter. Clypeus height about 1.9 times AME diameter. Leg I femur 1.35, patella 0.35, tibia 1.15, metatarsus 1.00, tarsus 0.50. Femur I about 5 times longer than wide. Leg formula 1243. Leg pale yellowish, femur I distinctly darkened, except at base. 3–5 small trichobothria dorsally on all tibia, 3–4 on tibia I–III, 5 on tibia IV. 2 prolateral and 1 retrolateral trichobothrium on palpal tibia. Stridulatory pick row on opisthosoma, under light microscopy, appears nearly straight, consisting of less than 10 modified setal bases. Epiandrous gland spigots in two clearly separate groups, number of fusules difficult to estimate under light microscopy. Palpal organ as in Figure 10A . Female ( paratype ): Total length 1.90. Prosoma 0.90 long, 0.65 wide, light to dark brown, center and narrow rim darker. Sternum 0.55 long, 0.45 wide, light to dark brown. Opisthosoma 1.25 long, 1.05 wide. Pattern as in male. Eyes subequal in size about 0.07 in diameter. Clypeus height about 2.1 times AME diameter. Leg I femur 1.15, patella 0.35, tibia 0.95, metatarsus 0.75, tarsus 0.45. Femur I about 6 times longer than wide. Leg formula 1243. Leg pale yellowish, femur I distinctly darkened, except at base, tibia I darkened distally. 3–5 small trichobothria dorsally on all tibia, 3–4 on tibia I–III, 4–5 on IV. 3 dorsal trichobothria on palpal tibia. Epigynum as in Figures 10B–C . Va r i a t i o n Male total length from 1.80–1.90, femur I from 1.35–1.40. Female total length from 1.90–2.55, femur I from 1.15–1.30. Coloration appears to vary somewhat, with one of the three female paratypes darker than the others, and with tips of all tibia darkened. Distribution Only known from the type locality. Natural history The collection label states: “Ψ theridiids in social agelenid web (among leaves) Ψ’s carrying egg sacs”. Based on this description it would seem that A. monskenyensis lives as a kleptoparasite in agelenid webs. However, kleptoparasitic living in A. monskenyensis would be unique among Anelosimus . We feel it is more likely that the web(s) was confused with those of social agelenids that are common in the area, and rather represented social (subsocial) Anelosimus web(s). In Madagascar several subsocial Anelosimus species were recently discovered in a small forest plot where the most common social spider was an agelenid ( Agnarsson & Kuntner 2005 ). The webs of these unrelated social spiders were so similar that we in some cases collected agelenid webs (without seeing the habitants) and brought back to the lab by mistake, thinking they were Anelosimus . Agnarsson & Kuntner (2005) speculated that the late discovery of this diverse group of Madagascar Anelosimus was in part due to collectors overlooking their webs, assuming they belonged to the common agelenids. One egg sac in the vial with the type material contained 13 eggs . Phylogenetics Anelosimus monskenyensis n. sp. has not been placed phylogenetically, but its morphology clearly indicates it belongs to the ‘filiform embolus’ clade ( Fig. 1 ).