Stabilimentum

Some Cyclosa spiders and Azilia vachoni construct conspicuous stabilimenta with attached detritus such as egg sacs and insect carcasses (mostly their prey), and also hang debris such as dried leaves from their webs.

The authors note that regardless of function, there is a high cost to building a stabilimentum, and therefore the benefit must be equally large.

[10] Another hypothesis is that the purpose of the stabilimentum is to attract the male of the species to the web when the female is ready to reproduce.

[13] At least one species has been observed to vibrate the web, while positioned in the stabilimentum when approached by a body the size of a human.

In contrast, the strongly UV-reflecting stabilimentum of the uloborid Octonoba sybotides was found to be attractive to Drosophila flies.

Stark[14] argued that although these hypotheses seemingly conflict, they might not be mutually exclusive, and suggested that we could take a hierarchical approach to model this problem: the predominant factor leading to stabilimentum production (i.e., the main function of the decoration) in each population might be different depending on the prey-and-predating context of that population.

Instead, he hypothesized that the visual signaling effect of stabilimenta might be derived from some non-signaling trait that is connected to other aspects of web-building behavior, such as silk disposition; this behavior was then selected preferentially to the specific ecological environment and therefore would be displayed through different patterns and functions among various habitats.

[citation needed] In Cyclosa argenteoalba, web decorations were found to support Stark's hypothesis above in that they do not attract prey and instead deter predators.

This was determined through experiments where the spiders produced longer silk decorations when there was an increased predation risk, but were not affected by the amount of available prey.