Reproduction and development of the spider Nephila edulis (Koch) (Araneidae : Araneae)

Abstract

The sexually dimorphic Nephila edulis breeds during the autumn (February-May), the large female producing one egg-sac per season, containing an average of 383 eggs. The web of immature females sometimes incorporates a stabilamentum. Mating behaviour can result in the death of the male and is different from the ritualized mating behaviour of N. maculata. The male of N. edulis always begins its mating sequence after a female has caught prey. N. edulis in the study site fed predominantly on leafhoppers, dealing with its prey by a stereotyped attack sequence. The egg-mass of N. edulis is laid in a complex egg-sac of yellow silk. Each 1.14-mm diameter egg is coated with minute, regular particles which may have water-resistant properties. The prehatching development time is long; 29 days at 20ºC and 42-87 days in the field. The external embryonic stages are similar to those of other araneomorph spiders. Pigmentation, developed in embryos of N. edulis after the germ band stage, is believed to be associated with the breakdown of yolk. The external changes during the first three posthatching instars are described. The emergence from the egg-sac at the third instar is correlated with the depletion of yolk reserves at this stage. The function of the egg-sac of N. edulis is not related to protection from extremes of temperature or humidity. The function is discussed in relation to protection of the eggs from predators and parasites.