Meeting Abstract
Contaminants decrease adhesive strength by interfering with substrate contact. Spider webs adhering to moths present an ideal model to investigate how adhesives overcome contamination because moth’s sacrificial layer of scales rub off on sticky silk, allowing the moths to escape. The Cyrtarachninae spiders evolved webs that overcome this limitation and are moth-specialists. We compare the adhesive performance of Cyrtarachne glue to more typical spider glues to understand how Cyrtarachne glue overcomes dirty surfaces. High-speed videos show that upon contact with moth-wings the low viscosity of Cyrtarachne aggregate glue allows it to seep beneath the scales and accelerate, spreading along the underlying cuticle due to capillary forces. The adhesive strength of most other spiders’ glues is maximized at a much higher viscosity that optimizes the contributions of spreading for surface contact versus cohesive strength. While the low viscosity of Cyrtarachne glue leads to rapid spreading how does it not sacrifice cohesive strength of the glue? Infrared spectroscopy showed a rapid loss of unbound water during initial spreading which may indicate drying of the droplet. Raman spectroscopy and optical microscopy support that the distribution of glycoproteins and salts is not homogeneous as found in other spider species. Instead, we hypothesize that rapid spreading of the liquid components of the glue relative to adhesive material leads to localized drying, increasing cohesive strength.
