By guest blogger Clint Penick, North Carolina State University
Insects wear their bones on the outside of their bodies. Their so-called “exoskeletons” provide rigid support and structure for muscle attachments similar to our own skeletons. But the exoskeleton also performs functions similar to our skin. Like skin, the exoskeleton is composed of multiple layers with pores and hairs that create a buffer between the inside of an insect’s body and the outside world (Fig. 1). With literally millions of insect species on Earth, the unique properties of insect “skin” are only beginning to be explored.
The first clue that insect skin (or, cuticle) could offer new insights into the way we think about body coverings comes from studies on the Namib Desert beetle, Stenocara gracilipes. The Namib Desert is one of the driest places in the world, but the air above the desert floor can be saturated with fog that blows in from the ocean. When fog blows in, the Namib beetle stands on its head to expose small bumps on its abdomen that attract water. The rest of the abdomen is covered with waxy grooves that channel the water to the beetle’s mouth. Engineers have now mimicked this process to build new devices that pull fresh water out of the air in regions where drinking water is scarce.
A more recent discovery related to insect skin comes from studies on the Saharan silver ant, Cataglyphis bombycina. The silver ant forages at temperatures that would kill most other insects, but silver ants are able to withstand the heat using a special coat of hairs (yes, insects have hair, though insect hairs are somewhat different from those in mammals). The hairs of the silver ant reflect most wavelengths of light but are nearly transparent to mid-infrared radiation—the wavelength ants emit as heat. This trick allows silver ants to reflect heat when they are in the open and then shed excess heat when they find a patch of shade.
Over the past semester, a group of students I have been working with at North Carolina State University have also become interested in the body coverings of ants. For hundreds of years, scientists have used differences in ant cuticle patterns to tell species apart, but very little is known about what these patterns do for the ants. We had a hunch that differences in ant cuticle could affect how species deal with pathogens, and we are now studying this in a genus of Australian ants that wildly differ in their cuticle structure (Fig. 2). We are extending this project to work with students from arts and design to make a catalog of different cuticle patterns. This is the first step in what we hope is a deep investigation into the properties of insect cuticle.