#22: Caterpillars

Litinsects #22: Caterpillars

Since you are freshly familiar with metamorphosis from my last posts, I will today be talking about caterpillars 🐛 and some structures that change drastically in appearance from before to after metamorphosis: legs.

Caterpillars are the worm-shaped larval stage of butterflies and moths. They have huge appetites; they mainly feed to grow and gain energy for their transformation into adulthood. In order to do this they need to get around, for which they use legs because only adult stages have wings. 

But insects only 3 pairs of legs, right? So where do all these extra legs come from all down the sides of their bodies? 

• Caterpillars have 3 pairs of TRUE LEGS, attached to their thorax, which are jointed and have little claws on the end. These legs are still present after metamorphosis, though they will have changed substantially

• Additionally, they usually have 2 to 5 pairs of PROLEGS, which are protrusions from the abdomen that caterpillars use to aid in movement and gripping surfaces. During metamorphosis these disappear, as they are an adaptation present only in the larval stage

Prolegs work sort of like Velcro. They have pads with tiny barbs on them that they use to attach to the surface they are walking on. Caterpillars don’t really use their prolegs to “walk”; instead they detach their suctioned prolegs, stretch their body forward, reattach their prolegs, and repeat. 

Prolegs also have sensory hairs so the caterpillar can feel what it is walking on. Since they only have simple eyes, this is the best way for caterpillars to sense obstacles in their paths.