Beguiling Beetles in the Wildlife Garden

Beetles are a very diverse insect order and many beetles are frequent flower visitors; they are pollinators, beneficial insects predating on problem insect populations such as aphids, as well as parasitoids of other flower visitors. See similar posts about Fantastic Flies and Wonderful Wasps

The two most common flower visitors are soldier beetles (Cantharidae family) and long-horned beetles (Cerambycidae family). Beetles visit flowers to feed on pollen and nectar. Some have hairs on their tongue tip that act like pollen brushes, but typically they use their mandibles for chewing pollen grains.

Beetle Life Cycles and the Greater Food Web – It’s All Connected
Many beetle larvae are wood-boring, feeding on wood fibers or the fungus that inhabits decaying wood. By leaving dead standing trees (snags), or downed tree logs on the ground (nurse logs) in your landscape, you are providing valuable habitat for beetle larvae and the birds who feed on the larvae such as woodpeckers. Many native bee species use the abandoned wood burrows made by beetle larvae as nesting sites. Some examples include leafcutter bees, Megachile spp., mason bees, Osmia spp. and carpenter bees, Xylocopa spp.

Banded Longhorn Beetles, Typocerus velutinus
Common on coneflowers, this beetle feeds on pollen and nectar, their larvae are wood-boring.

Beetles can sometimes be destructive; some are not delicate flower visitors by any means, their mandibles chew on flower parts and foliage causing damage in some cases. For example, these blister beetles, Lytta sayi, are destructive feeders on legume flowers such as wild white indigo, Baptisia alba.

POLLINATION

Many flower visiting beetles have hairy bodies where pollen grains attach aiding in the pollination of flowers. They often show a preference for white, cream or green colored flowers, with a strong, fruity or fermenting odor. The hard wings (elytra) provide some protection to beetles while they visit flowers. They are not easily scared off by other flower-visiting insects and will spend several minutes on a flower feeding on floral resources.

Locust Borer Beetle, Megacyllene robiniae

Locust borer beetles feed on pollen and are found on many goldenrod species in late summer. A possible survival strategy is to mimic wasps with black and yellow coloring, a good bird deterrent. The larvae of this beetle excavate tunnels in the wood of black locust trees (Robinia pseudoacacia).

Blister Beetles, Nemognatha spp.

These blister beetles are common on black-eyed susans, often feeding on nectar. They have strange looking mouthparts consisting of long maxillae that they use to suck nectar, they can also feed on pollen with their mandibles. Females lay their eggs on flowers, when the larvae hatch, they attach themselves to visiting bees and are carried back to the bee nests. The beetle larvae kill the bee larvae and consume the bee provisions of pollen and nectar.

Fire-Colored Beetles, Pedilus spp.
Fire-colored beetles are common flower-visitors in the spring. Larvae feed on fungi in decaying wood. Look for these beetles on flowers near woods often where blister beetles occur. Male fire-colored beetles will climb onto blister beetles, prompting them to release cantharidin, a defensive chemical. The male fire-colored beetles then lick the cantharidin off the blister beetle and use the chemical to attract females. When the male beetles mate with females, the cantharidin is transferred to the female. Her eggs are coated with cantharidin which helps protect them from predation.

PREDATION (BENEFICIAL INSECTS)

Soldier Beetles, Family Cantharidae
Soldier beetles visit flowers for pollen and nectar, they are very common in mid- to late-summer.Their narrow head, thorax, and maxillary tongue allow them to access flower nectar in fairly deep flower corollas.Considered a beneficial insect, soldier beetle larvae feed on aphids, fly larvae, small caterpillars, beetle larvae and grasshopper eggs. Some adults in this family also feed on aphids. One defense mechanism of soldier beetles is to secrete a chemical compound so they are unpalatable to predators.

Ladybird Beetles, Cycloneda spp.

Both adults and larvae feed on soft-bodied insects (mainly aphids) and are utilized in the biological control of aphids. Females can consume hundreds of aphids before laying eggs. These beetles overwinter in groupings as adults and emerge in spring. Look for ladybird beetle eggs laid near aphid clusters, often under the flowerheads.

PARASITISM

Wedge Shaped Beetle, Macrosiagon limbatum
A distinctive, triangular-shaped small beetle. Both male and female wedge-shaped beetles are found on native plants visited by wasps (and bees), where the female lays her eggs on the foliage. When an egg hatches the tiny first stage larva attaches itself to a visiting wasp or bee. The host carries it back to its nest where the beetle larva burrow into the host larva and live as an internal parasite.The developing wedge-shaped beetle larva continues to consume its host from the inside and eventually emerges from the host body. It then proceeds to feed on the host from the outside until the host dies.

Tiphiid Wasp, Myzinum spp.

These wasps visit late summer natives for nectar. Males have a menacing looking ‘pseudostinger’ on the end of their abdomen. Females burrow into the ground and lay their eggs on scarab beetle grubs which their larvae consume as they develop.

SPECIALIZATION

Milkweed Leaf Beetle, Labidomera clivicollis
Milkweed leaf beetles are one of several beetles who specialize feeding on the foliage of milkweed (Asclepias) plants. Overwintering adults emerge in early spring. Females typically lay their eggs on the underside of milkweed leaves; look for bright red to orange egg clusters. Larvae hatch and develop in several instar stages during the summer months and feed on milkweed flowers and foliage. Adults are again active in the fall preparing to overwinter.

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