“I found this bug (and a few of its friends) on a watermelon plant today” says this reader about the dark green caterpillar-like creature photographed below. She wonders if this is a roly poly larva, and asks if she will need to relocate the bugs or if they are okay to stay in her garden.

According to our reader, these creatures are about 1/4-inch long and a dark green color. She found a picture and article about roly poly larvae and wonders if this creature is at all in the same category. It is our opinion that this critter is not related to roly poly larvae, but is actually a leaf beetle larvae. Leaf beetles make up one of the biggest beetle families we know of; there are over 30,000 species! The adult beetles, as well as their larvae, will feed on the leaves of various trees, the species of tree depending on the species of leaf beetle. We do not know exactly which species the larva our reader found belongs to, but our best guess would be that it is a Brittle Bush/Encelia leaf beetle larva. The larvae of these beetles are the same dark green, glossy color, with the same segmentation and dots on the sides of their bodies. What our reader could do to confirm this identity is look at the larva from the side to see if it has rows of short, thin legs sprouting from the sides of its body.

Now, the diet of the leaf beetle larva consists primarily of tree leaves only, and thus it is mostly harmful only to trees. It should therefore not eat on our reader’s watermelon plant. It is likely that the beetle larva ended up on the watermelon plant accidentally; perhaps it just fell from an overhanging tree branch onto the watermelon plant. Alternatively, it may have crawled onto the plant in search of food. Of course, it is not impossible that the larva starts feeding on the leaves of the watermelon plant, nor is it impossible for our identification to be incorrect. So, if our reader would rather be safe than sorry, it might be a good idea to relocate the larvae as she suggested.

To conclude, the “bug” our reader found on her watermelon plant is a leaf beetle larva, and most likely a Brittle Bush leaf beetle larva. They are not harmful to humans or pets, and should not be harmful to watermelon plants either. Of course, our reader may also not want these crawling on her trees and eating their leaves either, so we are sure that whatever decision she makes with regard to relocating them will be the right one. We wish her the best of luck!