Number 71 • March 4, 2010 • Jeffrey K. Barnes

Order: Coleoptera
Family: Phengodidae
Genus and species: Phengodes spp.

GlowwormPhengodid male

The term glow-worm is applied to the beetle families Phengodidae and Lampyridae.  Both families contain species in which females are wingless and resemble larvae. Wingless females and most larvae of both families are luminescent, and eggs and pupae of some phengodids are also reported to glow. Phengodids are relatively uncommon New World beetles occurring from southern Canada to Chile. Larvae and larva-like females produce light from organs located on most body segments. Males are odd-looking winged beetles much smaller that their mates, they are generally short-lived, and they probably do not feed.  They have elaborate, feathery antennae that are used for locating females. In the fireflies – family Lampyridae – flashes of luminescence are used to attract mates. The purpose of luminescence in the phengodids is unknown, but it is hypothesized that it functions in defense, warning potential nocturnal predators that they are unpalatable, much as warning coloration advertises the fact that some day-active insects are unpalatable. Larvae and larviform females are predators found in wet soils. They apparently have a strong preference for millipede prey.