Subject: Beetle Variant
Location: Reston, VA
October 14, 2014 11:27 am
Hello! I have enjoyed several of your posts helping to identify bugs. A friend of mine found this beetle in in October in her garden, Northern Virginia. She raises Monarchs and wants to find out if this one is one of the caterpillar hunters – or other threat to butterfly life. It does not appear to be a ‘hunter’ and nor does it seem to match the photos I saw of the plain ground beetles. Look at the gold/orange coloring on legs and antennae. It also doesn’t seem to have the extended head of a ‘big head ground beetle’. We would like to know what variety it is and if it is friend or foe to our butterfly friends. Thank you so much!
Signature: many thanks, L Phillips
Dear L. Phillips,
Tell your friend this Bess Beetle in the genus Odontotaenius whose identity we verified on BugGuide, is no threat to the Monarchs. Caterpillar Hunters like the Fiery Searcher are very different looking. Members of the Bess Beetle Passalidae care for their young and they feed on rotting wood. According to BugGuide: “Lifestyle of this family is unique for beetles: live in small colonies where larvae are cared for by adults of both sexes. Long life cycle, apparently more than one year. Larvae eat a rotting wood pre-chewed by adults. (Some references state larvae eat feces of adults as well.) Larvae and adults also cannibalize injured larvae. Adults reported to fly very seldom, however they are capable of flight, contrary to statements in some sources. Adults are found at lights on occasion. They may disperse by walking, but have been observed flying under lights (image), and they are sometimes taken in light traps (MacGown and MacGown, 1996). A nuptial flight has been observed in Mississippi, with a group of 12-15 individuals flying at dusk, and one pair even mating in flight (MacGown and MacGown, 1996). Mating is also observed in the tunnels …. Both adults and larvae stridulate, and this is said to serve as communication between them. Adults also stridulate when picked up, and especially, blown on. Adults stridulate by rubbing abdomen against the wings. Larvae stridulate with reduced third pair of legs–these scratch against other legs.” Our editorial staff spent many family holidays in Reston in the early 1970s.