Web construction behaviour and ecological preferences of the Eurasian diving bell spider Argyroneta aquatica

The diving bell spider (Argyroneta aquatica) is the only known species of spider to live a wholly aquatic lifestyle. It constructs a three-dimensional web, dubbed the diving bell, which it fills with air collected from the water’s surface. The behaviours associated with the construction of such three-dimensional webs are largely understudied, in part because of their difficulty to dissect into discrete steps. There has been recent progress made in understanding the function of the diving bell as a gas exchange surface, and yet within that, the construction behaviours associated with this have seen little in the way of characterisation. It was hypothesised that the webs of these spiders must contain some emergent properties ensuring their functionality across each instance they were built. This study has demonstrated that the process can be divided up into four key steps. Certain aspects of the process remain more consistent than others across the species, regardless of geographic location and despite genetic analysis revealing a high level of variation both within and between populations. Some features of construction are shown to differ based on ontogeny and sex, females are more repeatable than males in most regards – especially in the time taken to construct a web - and show a preference for web reinforcement. Females appear to follow a more rigid time frame in terms of construction, with repeatability increasing when analysed over a shorter period. Though web construction varied within individuals, it does seem that the process in females is more repeatable when the physical condition of the individual and the environmental conditions they are building in are more consistent. Some features related to optimisation of the process were noted. Body size was shown to determine the number of air bubbles collected to fill the web in a presumed trade-off between size and diving ability. Ultimately, the process appears highly plastic, being dependent upon the dynamic form of the pneumatic surface, and the volatile environment they inhabit. Habitat preference data suggested the spiders rely far more on the vegetative substrate on which they build their web than on any factor of water quality as may have been assumed in some of the literature. This seems logical given the essential role of the diving bell in survival, and the necessary cover from predators the vegetation affords.