Fungus weevils are small to medium-sized, chunky, stubby-looking beetles that are generally egg-shaped, elongated, or oval. Like most other snout and bark beetles (weevils; in superfamily Curculionoidea), the head has a protruding beak, but in this case the beak is usually wide and flat (not thin and curved), with a pair of large pincer-like mandibles at the tip. The surface of the body and wing covers is often bumpy, lumpy, ridged, mildly spined, or pitted, often with patches of hairs. The overall color is usually brown, black, or gray, often mottled or banded with hair patches of contrasting colors (white, gray, rust, brown, and so on). Several species appear dark gray with white patches. Unlike many other snout and bark beetles, fungus weevils do not have elbowed antennae, though the antennae are usually club-tipped.
Similar species: There are eight North American families of beetles in superfamily Curculionoidea, and all of them are called weevils. The fungus weevils (family Anthribidae), discussed on this page, are just one of the weevil families. The most famous family of weevils are the snout and bark beetles (weevils) in family Curculionidae.
Common names can be confusing. Globally, there are about 390,000 species (that have been described) in 176 families of beetles (order Coleoptera). Many of these groups are called “fungus beetles.” And it doesn’t help that many fungus weevils in family Anthribidae are not associated with fungi.
Some of the other groups called “fungus beetles” include the pleasing fungus beetles (family Erotylidae), hairy fungus beetles (family Mycetophagidae), silken fungus beetles (family Cryptophagidae), minute brown scavenger beetles (also called “fungus beetles”) (family Latridiidae), and handsome fungus beetles (family Endomychidae). Besides all being beetles, none of these are necessarily closely related.
Adult length: from less than ¼ inch to ⅝ inch, varying with species.
Statewide. Different species may have different regional distributions within the state.
Habitat and Conservation
Like many other insects, fungus weevils are usually found near their various food sources. Not only do they eat these food plants and mushrooms in all life stages, but also they must lay eggs on or near their foods, so they tend to look for mates in the same locations. Adults of some fungus-eating species are known to overwinter under the bark of dead or dying trees that host those fungi.
Many are good fliers, and some species are attracted to lights at night.
The larvae of several species develop within and eat bracket or crust fungi, such as turkey tails and many polypore species, that grow on diseased or dead trees. You may find immature and adult fungus weevils beneath the bark of such trees.
But “fungus weevil” is an imperfect name for this group. Many species are not associated with fungi at all. Many eat leaves, flowers, fruits, twigs, branches, and other plant parts, with some eating new, developing plant parts, and others preferring dead, decaying plant parts. Some species eat flower pollen and/or flower receptacles and stems. Many specimens are collected by beating the branches (living or dead) of trees and shrubs and gathering the insects that fall off of the vegetation.
Important as decomposers of dead, decaying plant material. Also important as a link in the food chain between plants and fungi, and insectivores.
Some fungus weevils found in North America are nonnative, having been introduced from other parts of the world. A notable example is the European species Anthribus nebulosus, an unusual insectivorous fungus weevil that was purposefully introduced to the East Coast to help control scale insects. It is spreading in eastern states.
Some species are pests of crops and of stored foods (such as grain or coffee beans).
Fungus weevils follow the general life cycle of other beetles. Eggs are deposited on or near food sources, hatch into grublike larvae, then eat, grow, and molt through a number of larval stages. The next phase is a pupal stage, where the insect transforms into an adult beetle capable of mating and continuing the life cycle.
Fungus beetles usually function “under the radar” of most people, but they and the fungi they eat play important roles in decomposition. What if all the fallen branches, sticks, and dead trees didn’t break down into soil?
If you care about birds, then you need to care about insects. Most birds require abundant, diverse insect populations in order to feed their nestlings. Even birds that usually eat seeds or fruits switch to a diet of insects during nesting, a rigorous time when they and their developing chicks need additional protein in their diet.
Some of the fungus beetles are fun to see, with their dour, flat, ducklike bills and attractively marked, chunky bodies.
Bitterweed (Helenium amarum) is native to Texas and Louisiana, but it has rapidly increased its range across the southeastern United States and into Missouri. Its flowers are a favorite food of the fungus beetle Trigonorhinus limbatus vestitus, which is apparently a hybrid taxon (a “species” that arose from interbreeding of two closely related species). This fungus beetle, thanks in part to the rapid, aggressive spread of its food plant, has apparently been genetically swamping its two parent species, to the point where all the insects resemble the hybrid.
The fungus weevil Trigonorhinus tomentosus is associated with common ragweed (Ambrosia artemisiifolia), an abundant, weedy plant that is a major contributor to summertime hay fever. The adult beetles eat the pollen. Females deposit eggs into the male (pollen-bearing) flowers, and the grublike larvae chew into the stems.