Meeting Abstract

P1.113  Jan. 4  Influences of environmental factors on egg sack production: progeny, developmental time and sexual ratio of Black widows Latrodectus mactans and L. geometricus in Puerto Rico. HERNANDEZ-PASOS, Josue *; PEREZ-REYES, Omar; Univ. of Puerto Rico, Rio Piedras; Univ. of Puerto Rico, Rio Piedras josuehp@gmail.com

Two species of Latrodectus [L. mactans (Fabricius, 1775) and L. geometricus (Koch, 1841) (Aranae: Theridiidae)] that occur throughout the island of Puerto Rico showed infections in their ovoteca by a larvae of a parasitoid wasp. Larvae obtain eggs in one of two ways: direct penetration of an egg sack by first instar larvae that search for egg sacs in the field, or boarding adult female spiders and entering the spider�s egg sac while it is being constructed. Inside the egg sac, larvae pierce and drain the eggs. Analysis of the exoskeletons showed just some parts of the unborn spiders (legs or parts of the prosoma). When the larvae were observed, the unborn spiderlings or eggs were bitten or entirely eaten. Egg sacs of L. mactans and L. geometricus were collected from two sites of the island (Isabela and Cabo Rojo). A total of 498 spiderlings emerged from the lab egg cases (mean of spiderlings per egg sack = 62.25), with 345 spiderlings emerging from 6 field collected egg cases (mean = 57.5). Adults or pupae of the parasitic wasp, emerged from 21.40% of the field-collected egg cases. The percentage of infection at Isabela site was 27.52% while on Cabo Rojo was 0%. Differences in morphology, egg sack structure and environmental factors (temperature, humidity and salinity) were positively related with the infection rate among species and localities.