Get to know the beetle masters of planet Earth

By Gary Raham
Nature writer and Illustrator

Back to Gardening Articles List

Some people look for the first robin of spring, but if they had paid attention, they could have seen robins all winter – at least in Colorado.

I'm waiting for the first beetles to appear in my garden. Then I'll know that the heavy lifting of spring growth and renewal is seriously underway. Ants are already piling up dirt from their excavations and a few roly poly (sow) bugs cross the barren sidewalk plains in search of leaf mold among sprouting blades of grass, so the wait shouldn't be long.

As a biologist, I've learned humility. I represent one of the two million or so described species of plants and animals on the planet. If a person were to create a lineup of these species, every fifth one would be some kind of beetle. That's an impressive stat for shy six-legged critters that fly like armored trucks.

Beetles have plied their trades for 240 million years (predating dinosaurs and early mammals), and they partnered with flowering plants to monopolize most of the world's habitats. All hail the beetles! May they live long and prosper – and leave me a few veggies for dinner salads.

Like other insects, beetles walk with six legs, possess armored bodies with three segments (head, thorax and abdomen), usually have chewing mouth parts and two pairs of wings as adults. Nature engineered the first pair of wings to be tough and leathery. They cover the delicate flying wings like the hood of a Model T Ford – offering protection during wood boring and scavenging operations. The two outer wings create a midline seam where they adjoin over the beetle's abdomen.

Half of all beetles are weevils, with snouts not unlike anteaters for "nosing out" pollen and seeds. Beetles also possess a variety of antennae (usually with 11 segments) that may be beaded, knobbed, threadlike or feathery. Mouthparts, antennae, wing forms, body shape and leg details tend to define the 125 families and 500,000 species of beetles. Here are some Colorado beetles to look for in the back yard.

Colorado hosts 80 species of bark beetles, like the infamous pine beetle. They create luge-like trails (galleries) beneath conifer bark as they feed, and they become serious pests when conditions favor their multiplication.

Blister beetles sport long bodies with outer wings softer than those of most beetles. They love munching on lupines, locoweed and other members of the pea family as well as sunflowers. Ninety species live in the state. They ooze a chemical called cantharidin from their joints that discourages ants from attacking them. They can cause sickness in horses that eat hay garnished with blister beetle remains.

Carrion beetles (15 species), darkling beetles (130 species), dermestid beetles (35 species), and some scarab beetles (200 species) serve on garden clean-up crews. Carrion beetles dine on animal remains and fungi. Many species tend to roll excess food into balls and store it underground as food for their young.

Darkling beetles specialize in plant material. Flour beetles, like mealworms, eat grains and can be a pest in the pantry. Eleodes suturalis, a common darkling beetle of our grasslands, will stick its rear end up when approached and make a stink by ejecting chemicals from its posterior distasteful to potential predators.

Dermestid beetles are the only insects that can digest keratin, a tough protein component of hair, feathers and tendons. Home-owners used to find dermestid "carpet beetles" munching on wool carpets, but synthetic materials are not on their menu.

The 10-lined June beetle (up to 1.5 inches long) is a Colorado scarab beetle that eats decayed plant material. Some scarab grubs become garden pests when they eat the roots of crop plants.

Predatory beetles include soldier beetles and tiger beetles. One of Colorado's soldier beetles, a relative of fireflies, spends time on goldenrod pursuing aphids and other insects. The black road tiger beetle often wanders roads, sidewalks, parking lots and grasslands looking for lunch. As larvae they are lazier, sitting inside a soil burrow until something walks by so they can snatch it with their large mandibles.

For ostentatious elegance, I love longhorned beetles. Their "horns" are antennae that often stretch out as long or longer than the beetle's body. The milkweed longhorn hangs out on milkweed leaves and easily stomachs the plant's glycocide chemical defenses, making itself distasteful in the process. It advertises its unpalatable condition with a black-spotted red carapace and barber pole antennae.

Nearly everyone's favorite beetles, however, are the leaf beetles (with 425 Colorado species). The ladybug beetle can claim the highest cuteness coefficient. Environmentalists sometimes describe them as the pandas of the insect world – flagship species with an image that overcomes the knee-jerk "yuck" response to many insects. Ladybugs have voracious appetites for aphids, a characteristic that often endears them to gardeners (although another insect, the lacewing, is often a better choice for pest control). Other leaf beetles include the metallic gold-flecked tortoise beetles (that eat bindweed, by the way) and a leaf beetle called Trirhabda that eats rabbitbrush. Their larvae sport a deep metallic green skin that often stands out in sharp contrast to the yellow blossoms of the rabbitbrush.

Yes, spring is in the air and beetles will soon be in the bushes. Watch them and enjoy them as they rule the world. Humility is optional.