Scarab Beetles

About 1,700 species in North America north of Mexico.

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Male eastern Hercules beetle walking in grass
Male eastern Hercules beetles (Dynastes tityus) can be nearly 2½ inches long, counting the horns, which are used for male-male contests, much like the horns of deer and elk. Females lack the horns.
Family

Scarabaeidae (scarab beetles) in the order Coleoptera (beetles)

Description

The scarab beetle family is very large, with breathtaking variety — and often great beauty. Although many are black, brownish, or drab, many scarabs are colorful, some with iridescent greens and other colors, others looking as if they were covered with shiny enamel paint. They are oval or elongated, stout, usually with rounded backs, and have clubbed antennae with segments that can press tightly together or can be fanned open like leaves. In several species, the males (sometimes females, too) have pointy horns. Several species are quite large.

The larvae of most scarab beetles are whitish, C-shaped grubs that live underground or in other protected places. The heads are often brownish or black, and they have three pairs of legs.

Size

Length: from less than ¼ inch to 2 inches (adults); to about 2 inches (larvae) (varies with species).

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Delta flower scarab clinging to flower
Delta Flower Scarab
The delta flower scarab (Trigonopeltastes delta) got its name from the bright yellow triangle on its pronotum (“delta” is the Greek letter that’s a triangle). The yellow pattern might help protect it, since the beetle resembles a stinging wasp.

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Green June beetle on goldenrod
Green June Beetle
Green June beetles are common in Missouri. These large, metallic green beetles buzz loudly when they fly. They are attracted to ripe and rotting fruit and compost piles.

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Dark flower scarab clinging to a flower
Dark Flower Scarab
The dark flower scarab (Euphoria sepulcralis) is a scarab beetle that apparently eats pollen, nectar, and perhaps other parts of flowers in late spring, sometimes becoming an agricultural pest. The larvae grow up beneath manure or other decaying materials.

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May beetle on wood
May Beetle (June Bug)
Clumsy walkers and fliers, May beetles are usually brownish and are attracted to lights at night. These common beetles are named for the months they are most numerous.

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Dung beetle rolling a dung ball
Dung Beetle
Horses, cattle, dogs, and deer all drop manna from above to eager dung beetles, which collect, hoard, and guard the precious organic materials left undigested in the pile.

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Male eastern Hercules beetle on bark
Eastern Hercules Beetle (Male)
The eastern Hercules beetle (Dynastes tityus) is huge and strong. The larvae eat rotting heartwood, usually of deciduous trees, and the adults eat rotting fruits and tree sap. Males have two forward-pointing horns used for battling other males for the best breeding sites.

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Japanese beetle on a leaf
Japanese Beetle
Despite its decorative bronze wing shields, metallic green thorax, and black-and-white striped abdomen, the Japanese beetle is a serious agricultural pest.
Habitat and conservation

The various scarab beetles occupy different habitats. Some are nocturnal; others are active during daytime. Many are good fliers and are attracted to lights at night. Scarabs that feed on decomposing materials, such as dung beetles and green June beetles, are seen on rank and rotting materials. Plant feeders are found on their favorite species of plants: rose chafers on members of the rose family, the delta flower scarab on members of the carrot family, etc. Others eat underground plant parts.

Foods

Adults feed on various materials, according to species. The mouthparts are mostly adapted for chewing. Some eat decaying materials such as manure, carrion, rotting and fermenting fruits, and composting plant material. Some eat fungi and mushrooms, or sap. Others burrow into the soil and chew plant roots. Some eat flowers, pollen, and nectar, some species pollinating flowers in the process. Many eat leaves and fruits. The larvae of most eat decaying materials or plant roots.

image of Scarab Beetles Distribution Map
Distribution in Missouri

Statewide.

Status

Common. Some, such as the introduced Japanese beetle, are serious agricultural pests. The root-eating “white grubs” of some species disfigure golf courses and lawns. Meanwhile, other scarabs are quite welcome, considering human interests. Dung beetles, for example, save US agriculture hundreds of millions of dollars annually for helping to clean pastures and barnyards. Most scarabs help tremendously in helping to break down decomposing materials and thus nourish the soil.

Life cycle

Mating often takes place near the food material that the offspring will need. The elaborate antennae of the adults are used to smell and locate this food. Fertilized females deposit eggs in the soil, on the rotting compost heap or dead log, on the manure pile, etc. The grubs eat and grow, in some species for years, sometimes descending lower into the soil to overwinter. When fully grown, the larvae pupate, then emerge as adults, which will fly, mate, and lay eggs.

Human connections

Some types of scarabs are pests to lawns, gardens, and crops. Many others help to decompose materials in the compost heap. Meanwhile, the grubs are a free, live fishing bait. One type of scarab was revered in ancient Egypt. Scarabs are special favorites among insect collectors.

Ecosystem connections

Many animals root out and eat the grubs, including skunks, moles, and birds such as crows and grackles. Many other animals, including birds, bats, and frogs, eat the adults. Several types of flies and wasps are parasitic on the adults and larvae, laying eggs on them that hatch and devour the host.