Along the Path

By Susan Rothrock Deo

Photo by Emile Fiesler

What is that crawling between the leaf litter? It’s dark and shiny and scuttles under the leaves. It’s a darkling beetle in the coastal sage scrub. Our darkling beetles are black and are about three quarters of an inch long. Their wings are fused so they can’t fly. The adults have chewing mouth parts and feed on dead plant and animal material: our sage scrub “garbage collectors,” as one friend calls them. They are often found under California buckwheat (Eriogonum fasciculatum), which is one of the keystone species in coastal sage scrub and other sagebrush ecosystems. 

Ha, ha! What is he doing now? He’s standing on his head! When threatened, darkling beetles stand on their heads and point their rear ends in the air. Some species release an offensive smell when they do this, which is why some people call them “stink beetles.” Our local ones do have a bad taste so many birds and small mammals leave them alone. 

There are about 20,000 species of darkling beetles worldwide, which can be kind of confusing if you use this common name to identify them. They make up the Family Tenebrionidae. The name comes from the Latin word Tenebrio which means “seeker of dark places.” This makes sense since they are scavengers and often found hiding in leaf litter or under rocks. They help the environment by getting rid of lots of dead materials! There is even one species of darkling beetle from East Asia that scientists are studying because it can eat Styrofoam. This is exciting for our planet because Styrofoam is a type of plastic that takes hundreds of years to decompose on its own. Darkling beetles, both adults and larvae, can also be pests: eating stored goods like flour, grains, etc. 

Darkling beetles undergo full metamorphosis like butterflies do: egg, larvae, pupae and adult. Their larvae are commonly known as mealworms. Maybe you buy mealworms from the pet store to feed your pet lizard or bird. (These pet food mealworms are different species from our local darkling beetles.) The local adult beetles and their larvae provide food for many wild creatures in the coastal sage scrub or sagebrush, like coyotes, foxes, hawks, snakes, ravens and crows.

Darkling beetles are one of many families of beetles in the Order Coleoptera, the largest insect order. Almost 40% of all insects are beetles, about 350,000 species. That’s about 25% of all animal life on land. 

Be on the lookout for darkling beetles when you’re out walking in the sage scrub. Even though they are small, they play an important role in our local ecosystems.