Should I stay or should I fly: Aerial dispersal in a funnel-web wolf spider from the grasslands of southern South America

Abstract

Ballooning is a mechanism of aerial dispersal present in some groups of spiders. By releasing silken threads that are blown by the wind, spiders can travel long distances through the air. Aglaoctenus lagotis is a wolf spider that lives its entire life associated with a funnel-web, despite the wandering habit that characterizes species in this family. We can find two forms of the species in Uruguay, one of them a strict inhabitant of grasslands of Uruguay. The high habitat specificity and the spiderlings observed surrounding the maternal web suggest a low aerial dispersal capacity in this species. In this study, we tested whether A. lagotis spiderlings are capable of dispersing by ballooning. We conducted laboratory and field experiments during the day and night, to record the occurrence of ballooning and typical behaviours that precede ballooning. We recorded ballooning both in the laboratory and in the field, and it was more frequent during the day. Although it has been reported repeatedly in species from this family, we never observed the pre-ballooning tip-toeing behaviour in A. lagotis. Ballooning was preceded by dropping on dragline, considered a behaviour that could generate aerial dispersion of lesser distance than that generated by the tip-toeing. In this paper, we shall discuss the implications of this form of aerial dispersal, considering that the species analysed is a web wolf spider.