Web stickiness optimised to humidity

Blundering into a sticky spider’s web is unpleasant enough, evenwhenyouare large and can tear free. But for smaller creatures, impacting a web is a death sentence. Brent Opell and colleagues from Virginia Tech, USA, explain that the stickiness of a web depends on the stretchiness of the adhesive globules that are dotted along the spiral thread. ‘When an insect flies into an orb web, its legs, wings and body present different textures to theweb’s sticky threads and the insect’s struggle to escape generates forces whose magnitude and direction change rapidly’, says Opell. Previous labbased experiments had shown that the stickiness ofweb glue could be optimised to the humidity of the spider’s natural environment, as the stretchiness and adhesion of the droplets changes as the humidity alters. But what could this natural variationmean inpractice for snared insects; could variations in local humidity affect the survival chances of a thrashing fly?