File: <anthribi.htm>

COLEOPTERA, Anthribidae.

The "fungus weevils" are a small family that is distinguished morphologically by having a broad and flat beak. Larvae of some species inhabit woody fungi while others occur in corn smut and wheat smut, and others in dead wood. Adults are found under old bark or on dead twigs (Headstrom 1977, White 1983).

Species on the genus Brachytarsus (= Anthribus) have been reared from lecaniine Coccidae. Yano (1915) first reported on the predaceous behavior and life history of B. niveovariegatus Roel. attacking the Chinese wax scale, Ericerus pela Chev. in Japan. During May-June ca. 50% of female scales contained mature Brachytarsus larvae, pupae or adults in the egg chamber. Adults emerged during late June, and the remains of host scales were conspicuous because of the large, circular emergence holes on the dorsum. Silvestri (1919b) found B. fasciatus Foerst. common as a natural enemy of Eulecanium coryli in south Europe, where a maximum parasitization of 50% of scales occurred. Oviposition is mainly in April when a considerable number of eggs are present beneath host scales and the beetle egg is apparently laid among them. Female beetles feed on the body fluids of the host scales and also on the eggs. The larvae are restricted entirely to the cavity underneath the individual host scale and are dependent on the eggs found there for food. Therefore, the relationship is identical with that of the chalcidoid Scutellista cyanea Motsch. and its host Saissetia oleae Bern. The larva is weevil-like and robust, with the legs being represented by small conical protuberances. The cycle from egg to adult is around 2 months. Adults appear in June and persist without oviposition until hosts of the proper stage become available the following spring. Brachytarsus nebulosus Foerst. is also a natural enemy of several other species of lecaniine Coccidae in Europe (Prell 1925).

Clausen (1940) noted that neither of the above researchers observed actual oviposition, although Yano assumed that the eggs were placed on or in the vicinity of the host scales and that the young larvae later penetrated the egg chamber. Silvestri believed that they were laid beneath the margin of the scale and into the chamber by means of the extensible ovipositor. Clausen (1940) observed oviposition of B. niveovariegatus in both field and laboratory, in E. pela and several species of Kermes. The feeding habit of the female was found to have an intimate relationship with oviposition. The female breaks the hardened integument of the host scale and feeds on the body contents, after which she reverses her position, thrusts the ovipositor into the wound and through the thin ventral body wall, and places her egg within the egg chamber. The beetle egg is usually found adhering to the body wall of the host at the point of penetration of the beetle's ovipositor. The feeding wound is quite large, but it often heals over and normal oviposition by the scale is possible, though a large number die from their injuries.

Young beetle larvae feed only on the eggs. Later, after the host female dies, they feed extensively on body tissues also. When hosts are killed by injury associated with feeding of the female beetle, the larva may develop largely as a scavenger rather than an egg predator.

Only a single B. niveovariegatus develops in a host, even though the latter may be quite large and have sufficient eggs to bring several beetles to maturity. Therefore, the degree of control exercised is not as high as the 50-70% of scales attacked wound indicate (Clausen 1940/1962). In B. niveovariegatus and B. fasciatus, there is thought to be only a single annual generation, at least on the above single-brooded hosts. Adults emerge late in June, persist in that stage through winter and appear for oviposition the following April-May.

References: Please refer to <biology.ref.htm>, [ Additional references may be found at: MELVYL Library ]

Headstrom, R. 1977. The Beetles of America. A. S. Barnes & Co. London & NY. 488 p.

White, R. E. 1983. A Field Guide to the Beetles of North America. Houghton Mifflin Co., Boston. 368 p.