The potential role of web-based putrescine as a prey-attracting allomone

The use of prey-attracting allomones is likely to be an effective foraging strategy for sit-and-wait predators. Despite this, the production and efficacy of such allomones have rarely been documented. Previous investigations into the chemical composition of spider silk have revealed the presence of a number of potential allomone chemicals such as the amide putrescine, a foul-smelling organic compound. Putrescine is attractive to several terrestrial invertebrates, many of which are also typical prey species of spiders, but whether prey attraction is an underlying mechanism promoting its inclusion in web silk is currently untested. Here, we artificially increased the amount of putrescine in the web silk of female Argiope keyserlingi and assessed the resulting variation in prey interception of normal versus putrescine augmented webs under seminatural field conditions. We demonstrated that webs misted with a putrescine solution captured significantly more prey than webs misted with a control solution and also found differences in prey capture rates between individuals from different populations. This not only suggests that web-bound putrescine acts as a prey attracting allomone, but also that there is population level variation in the web-based foraging strategies of these spiders.