Caterpillar proleg

Spike Walker

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Photomicrograph of the base of a silkworm caterpillar's proleg. Prolegs are present in most larval forms, or caterpillars, of insects in the order Lepidoptera. The prolegs are short, stubby structures that grow from the underside of the caterpillar's abdomen. Prolegs disappear as the caterpillar grows, while the three pairs of true, jointed legs remain through adulthood.

What do the hooks do?

Each proleg has a circle of hooks ('crochets'), seen here in yellow and orange. The hooks assist in grip and locomotion, enabling caterpillars to climb up vertical surfaces. Caterpillars can have up to five pairs of prolegs. They act a lot like Velcro, sticking to surfaces with a tight grip. Prolegs can also help caterpillars crawl through narrow spaces or push through soil.

How was this image created?

Spike Walker created this image using a light microscope and a technique called differential interference contrast (DIC) illumination, which creates the brilliant colours you can see. DIC is also known as Nomarski illumination, after its inventor, George Nomarski.

The technique is used to enhance the contrast in unstained, transparent samples. This particular sample came from Spike's slide collection, and was made in the middle of the 20th century. For more information on light microscopy, view our video featuring Spike himself.