Life History and Seasonal Change in the Frequency of Dimorphic Stabilimenta of the Orb-web Spider, Octonoba sybotides (Uloboridae)

Abstract

The life history and reproductive activity of the Uloborid spider Octonoba sybotides were investigated. The seasonal change in the size distribution of the O. sybotides population at the study site showed that this spider has two generations per year: an overwintering generation and a summer generation. The overwintering generation hibernates from late November to early March as the juvenile stages. The duration of egg incubation varied greatly through the reproductive season, and seemed to be related to the total effective temperature. The number of eggs in each egg sac was significantly correlated with the weight of the mother. O. sybotides constructs a horizontal orb-web that frequently contains dimorphic stabilimenta (spiral and linear). The weights and condition indices of spiders showed that the spiders on webs with spiral stabilimenta to be in poorer energetic condition than spiders on webs with linear stabilimenta. The proportion of spiders on webs with spiral stabilimenta was negatively correlated with the prey abundance in their environment. The frequencies of spiral and linear stabilimenta in a population seem to be influenced by prey abundance, and prey-limited conditions induce the majority of O. sybotides to construct webs with spiral stabilimenta.