Insect cuticular hydrocarbon composition influences their interaction with spider capture threads

Abstract

Insects represent the main prey of spiders, and spiders and insects co-diversified in evolutionary history. One of the main features characterizing spiders is their web as a trap to capture prey. Phylogenetically, the cribellate thread is one of the earliest thread types that was specialized to capture prey. In contrast to other capture threads, it lacks adhesive glue and consists of nanofibres, which do not only adhere to insects via van der Waals forces but also interact with the insects’ cuticular hydrocarbon (CHC) layer, thus enhancing adhesion. The CHC layer consists of multiple hydrocarbon types and is highly diverse between species. In this study, we show that CHC interaction with cribellate capture threads is affected by CHC composition of the insect. We studied the interaction in detail for four insect species with different CHC profiles and observed a differential migration of CHCs into the thread. The migration depends on the molecular structure of the hydrocarbon types as well as their viscosity, influenced by the ambient temperature during the interaction. As a consequence, adhesion forces to CHC layers differ depending on their chemical composition. Our results match predictions based on biophysical properties of hydrocarbons, and show that cribellate spiders can exert selection pressure on the CHC composition of their insect prey.