Please refer also to the following link for details on this group:
Cucujidae: Link 1
Prostomidae (= Passandridae).-- The Prostomidae are often included with the Cucujidae. Several species of this small group have the entomophagous feeding habit, which has developed in some cases into an obligate parasitism. Catogenus rufus F. larvae are true external parasitoids of the pupae of certain cerambycid borers and of those of the braconid parasitoids attacking the same hosts (Fiske 1905). Scalidia is also known to develop parasitically (Clausen 1940/62)
These insects are sometimes called flat bark beetles are a family of distinctively flat beetles found worldwide under the bark of dead and live trees. The family consists of about 40 species in four genera.
They have elongated parallel-side bodies ranging from 6 to 25 mm in length. Most are brown colored, while others are black, reddish or yellow. Heads are triangular in shape, with filiform antennae of 11 antennomeres, and large mandibles. The pronotum is narrower than the head. Both larvae and adult live under the bark, otherwise little is known of their habits.
The family was formerly larger, with subfamilies Laemophloeinae, Silvaninae, and Passandrinae (and some tenebrionoid genera mixed in), but recent revisions have raised the subfamilies to family status.
These "flat bark beetles" show diverse food habits, and many species live in grain and grain products. The cosmopolitan Cryptolestes ferrugineus Steph. utilizes whole or milled grain, but sometimes it attacks other insects or is a scavenger (Sheppard 1936). A high oviposition rate was found in females that had fed only on the eggs of the angoumois grain moth. Larval development was most rapid when insect food was available. Many species are completely predaceous and attack wood-inhabiting Coleoptera, mainly Scolytoidea, while some are also phytophagous. Some species feed on termites (Clausen 1940/62) and mites. Species of Catogenus are parasitic in Braconidae (Borror et al. 1981).
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Arnett, R. H., Jr., M. C. Thomas, P. E. Skelley & J. H. Frank (eds.). 2002. American Beetles, Vol II: Polyphaga: Scarabaeoidea through Curculionoidea. CRC Press LLC, Boca Raton, FL,
Dillon, E. S. & L. Dillon. 1961. A Manual of Common Beetles of Eastern North America. Peterson & Co.
Thomas, M. C. "Cucujidae", in Ross H. Arnett, Jr. and Michael C. Thomas, American Beetles (CRC Press, 2002), vol. 2