To learn how to make glues that work well even in humid environments, where most adhesives tend to lose their stickiness, scientists are gathering clues from spider glue. Spiders rely on sticky drops of glue dotted along their webs to snare insect prey. If a spider wants to eat regularly, that glue has to work well regardless of humidity. Researchers led by the University of Akron’s Ali Dhinojwala studied five spider species, each of which lives in an area with a different humidity. They found that each spider’s glue achieved its maximum stickiness in the humidity of its native environment (ACS Nano 2015, DOI: 10.1021/acsnano.5b05658). High-speed photography revealed that the spiders achieved maximum stickiness by modulating the glue’s viscosity. As humidity increases, the glue’s viscosity decreases. There is a sweet spot for each spider where its glue has just the right viscosity for catching prey. The spiders use different types and amounts of hygroscopic organic salts to achieve the best glue viscosity for the humidity of their habitat.