Postembryonic development and population parameters of Alpaida veniliae (Araneae, Araneidae), reared in the laboratory

Abstract

We studied the postembryonic development from hatching to the adult stage and determined population parameters of Alpaida veniliae. It is one of the most abundant species of the orb-weaving guild of the spider community of soybean crops in Buenos Aires province, Argentina. The first three instars occurred inside the egg sac, and instar IV (spiderlings) started the dispersion from it. The female of Alpaida veniliae achieved greater adult size and adult longevity than the male. Mean fecundity, mean number of egg sacs per female, mean number of eggs per egg sac, as well as the net reproductive rate, the intrinsic rate of increase (r), the generation time (T), and the reproductive values (V _x) of three cohorts were determined under laboratory conditions, indicating a high capacity for growth. Their biological and ecological attributes indicate the importance of conservation of this predator as a natural enemy of soybean crop pests.

Keywords:

• spiders
• generalist predators
• soybean
• life history traits
• population growth rates

Acknowledgements

We thank R. Sosa and A. Cabrera for their valuable assistance in the field and laboratory work. We also thank H. Levy (Harvard University, Museum of Comparative Zoology) for taxonomic determination of spiders. This research was supported by the National Agency of Scientific and Technological Promotion from Argentina (ANPCyT).