It’s a Bessbug!
Fig. 1. Adult patent-leather beetle from Martinsville, Virginia. A pair of adults was observed in a well-rotten hardwood log in early spring 2015 (photo by K. Ivanov).
Bessbugs(= patent-leather beetles; family Passalidae) are a small, mostly tropical, group of unusual beetles most closely related to scarabs and stag beetles. About 500 species have been described worldwide of which only 4 occur in America north of Mexico. These include the widespread Odontotaenius disjunctus (Fig. 1) confined to deciduous forests of Eastern US; the Florida endemic O. floridanus; and two neotropical species of Passalus which were collected in Arizona at the turn of the 20th century but have not been seen since (Schuster 1983).
Unusual among Coleoptera, most species exhibit sub-social behavior in which multiple adults (parents and young adults) live together in small family groups that cooperate in offspring care. The common name bessbugs is derived from the ability of the adults to produce audible squeaking sounds when disturbed (“bess” from the French baiser, to kiss). These acoustical signals (stridulation) are produced either by rubbing the wings over rough patches on the abdomen (adults), or by by rubbing the vestigial hind pair of legs against the middle legs (larvae).The sounds are used for communication between the members of the colony. Upon closer inspection, a diverse assemblage of harmless phoretic mites can often be seen living on the exoskeleton of these beetles.
Our only species (a.k.a. the horned passalus) is relatively large, roughly cylindrical, bug reaching just over 1 ½ inches in length.The adults are easily recognized by the pronounced curved horn on the head, and the fringe of golden hairs on the middle legs, and edge of pronotum (Figs.1 and 2).
Fig. 2.A pair of O. disjunctus taken by K. Hans in Florida’s Apalachicola National Forest in 2008 (photo by K. Ivanov).
The body of older adults is jet black and shiny (hence the common group name patent-leather beetles) while newly emerged individuals are bright red, a color which they retain for the first few weeks of their life (Fig. 3).
Fig. 3. Odontotaenius disjunctus specimens form VMNH’s insect collection showing both older (black) and younger (red) individuals (photo by K. Ivanov).
Horned passalus beetles are generally found inside old logs and stumps in advanced stages of decomposition where they excavate tunnels and feed on decaying wood. These beetles mate in the wood galleries, where eggs are laid, and larvae develop. The adults take care of the larvae which they feed pre-chewed wood, and help in the construction of their pupal cases. Newly emerged adults will typically stay within the parent galleries for a limited period of time, and upon maturation will disperse (fly) to start a new colony.
These beneficial insects are important members of woodland communities where they participate in the decomposition of downed woody debris and thus speed up the return of nutrients to the soil. Although fairly common, these insects are rarely seen by the casual observer due mostly to their secretive lifestyle. The larvae can be found throughout summer, while the long-lived adults are likely to be encountered at all times, during the warmer parts, of the year.
So next time you come across an old log, stop and take a closer look. Maybe you will be lucky enough to encounter a pair of these fascinating critters.
Schuster, J.C. 1983. The Passalidae of the United States. The Coleopterists Bulletin 37(4):302-305.