Christopher Carlton, Huval, Forest, Reagan, Thomas E.
The man biter is a member of the minute brown fungus beetle family (Latridiidae). Adults are approximately 1/25th of an inch (1 mm) in length, with slender foreparts (head and thorax) of the body. Viewed from above, the head is somewhat rectangular in outline, and the thorax is broadly heart shaped. Small, bulging eyes are visible on either side of the head. The thorax and head of most specimens are covered by a white waxy secretion produced by glands located on the surface of those body parts. This secretion is lost in alcohol-preserved specimens. The abdomen is covered by the hard wing covers (elytra) that are actually the modified forewings in beetles. The elytra are broader than the head and thorax, and elongated ovals in outline. Regular rows of course, round punctures are present on the elytra. Though difficult to observe in such minute insects, a pair of slender antennae and six legs are present, as typical for insects.
Larvae are slender, soft, pale-bodied insects, up to 1/15th of an inch (1.5 mm) in length and possess scattered, long, hairlike setae.
Numerous species in the family Latridiidae may be found in circumstances similar to those where the man biter is found, and many are similar in overall shape and size. Correct identifications require microscopic examination by a knowledgeable specialist. The family name Latridiidae is often spelled “Lathridiidae” in older publications.
Adult man biter, Louisiana State Arthropod Museum.
In many parts of the world, minute brown fungus beetles occur naturally in moldy organic matter in forests, grasslands and a variety of other habitats. They are especially common in areas that are regularly slightly moist. Eggs are laid within the organic matter, and the larvae graze on fungal hyphae, spores and crusty fungal substrates. Adults and larvae of some species feed on slime molds. Under optimal circumstances, the life cycle requires one month or slightly less from egg to adult — longer under cool conditions and shorter when warmer. Adults and larvae are often found together, and large populations may be present in conditions that favor fungal growth. The man biter occurs in natural habitats in the southern U.S. but is more commonly encountered in residences and other human-made structures.
The common name “man biter” derives from the probing habits of adults when they find their way onto human skin. Although they do not feed on humans, they have a habit of testing the surface with their tiny but surprisingly effective mandibles to determine whether or not something edible is present. Many beetles will occasionally bite to test the surface of skin, but this species, Eufallia seminivea, is the only member of the household-infesting minute brown fungus beetles that has been repeatedly documented as a source of bites. The generally accepted common name “man biter” is misleading, in that it is an equal opportunity biter of either sex. When populations are high, adult beetles may concentrate in areas of high humidity, such as bathrooms, and bite unsuspecting residents. Published reports have documented persistent inflammation and itching at the site of the bites, but they are not considered medically significant.
In addition to the man biter, several other species of minute brown fungus beetles often infest structures. Their presence is a positive indication of mold growth somewhere in the building, but the source of the fungus can be difficult to determine. In one case, a related species of minute brown fungus beetle, the common plaster beetle (Dienerella filum), was present in large numbers in a hospital. The infestation was eventually traced to fungal growth in the filters of the air conditioning system. In that case, the beetles were a secondary problem that indicated a potentially more serious problem of mold in air conditioning components.
The minute size of these beetles can make them particularly hard to observe and correctly identify, leading to inappropriate and unnecessary treatments for fleas, bedbugs or other potential indoor biting insects. Chemical treatments following the discovery of man biters or other minute brown fungus beetles in dwellings may temporarily eliminate exposed individuals. Long-term management requires identification and elimination of the fungal substrates the beetles depend on for development. Dehumidification is often a successful strategy in dealing with mold problems that are obvious and accessible. Inadequately cured drywall is a common source of infestations in recently constructed or renovated houses. Aggressive dehumidifying often eliminates the problem in such cases. Extensive mold problems revealed by large populations of fungus-feeding beetles, especially in older structures, may require a professional mold mitigation service.
Carlton, C. E. 1988. Deinerella filum (Aubé) (Coleoptera: Lathridiidae), a potential pest of air conditioning systems. The Coleopterists Bulletin 42: 263-264.
Parsons, C. T. 1969. A lathridiid beetle reported to bite man. The Coleopterists Bulletin 23: 15.