Ripiphorus fasciatus (Say)

Rhipiphorus fasciatus - dorsal habitus.

Introduction & Bionomics

The Ripiphoridae are a very remarkable family of beetles which are endo- and ecto-parasites of various genera of bees. Falin (2002) provides an excellent summary of the known biology of the family and Linsley et al. (1952) did the definitive study of the biology of a member of the genus Ripiphorus (R. smithi) which is presumed to be similar to that of other members of the genus.

Females emerge in the course of the summer and after mating deposit between 6 & 15 eggs into the buds of an unopened flower (dissected females have 850+ eggs). Eggs hatching is synchronized with the opening of the flowers and the visitation of bees. The first instar larva is very active and holds itself erect on the apex of the abdomen in the presence of insect activity on the flower. One a suitable host is encountered (and different species and genera of Ripophoridae specialize on different genera of bees) the larva attaches itself and is carried back to the host nest.

Ripiphorus fasciatus - lateral habitus.

Once there it enters a cell and waits on the pollen mass for a host egg to be laid and hatch. It then penetrates the first instar larva and lives as an endoparasite, growing progressively more distended but not moulting. It overwinters in the mature been larva and when the bee enters its pre-pupal stage it grows quickly and emerges from the mesothorax of the bee, moulting into second instar. This second unsclerotized instar curls around the host and begins to consume it, undergoing four subsequent moults (six instars) until the host is consumed. Then it pupates and emerges as an adult after circa 12 days. After waiting in the pupal cell for an additional day it exits the hive and mates, usually living in the field as an adult for only 1-2 days.

Ripiphorus in Canada

Ripiphorus fasciatus - view of wings.

Six genera of Ripiphoridae are known in North America and of these, only three (Pelecotoma, Macrosiagon, and Ripiphorus) are recorded in Canada. Seven species of Ripiphorus are known from Canada and three of these, R. fasciatus (Say), R. walshii (LeConte), and R. zeschii (LeConte). Hitherto none of these species have been recorded from Atlantic Canada (Campbell 1991).

Pictured is a specimen of Ripiphorus fasciatus (Say) collected by Reginald Webster on July 18, 1998, 3.5 km southwest of the junction of Highway 101 and the Charters Settlement Road, York County, New Brunswick, Canada. This is on of the first records of the species, indeed of the whole family, from Atlantic Canada. Majka et al. (2006) reported new records of this species from Maine, New Brunswick, and Nova Scotia.

Ripiphorus fasciatus - head & antennae.

Description

Note the many distinctive features of these unique beetles. The elytra is extremely short leaving the large, unfolded wings exposed and giving the beetles a superficially dipterous (fly-like) appearance. The body of the beetle is very thick and has a "humpbacked appearance. The abdomen curls under the body and the pygidium faces ventrally. The antennae in males such as this are bi-flabellate and those of females (such as the one picture here) are pectinate. The eyes are large and protruding.

References

Campbell, J. M. 1991. Rhipiphoridae: Wedge-shaped Beetles. In: Bousquet, Y. Checklist of Beetles of Canada and Alaska. Agriculture Canada Publication 1861/E. pp. 250-251.

Falin, Z. H. 2002. Ripiphoridae Gemminger & Harold 1870 (1853). In: Arnett, R. H., Jr., Thomas, M. C., Skelley, P. E., and Frank, J. H. [Eds.]. 2002. American Beetles, Volume 2: Polyphaga: Scarabaeoidea through Curculionoidea. CRC Press, Boca Raton, USA. pp. 431-444.

Linsley, E. G., MacSwain, J. W., and Smith, R. F. 1952. The life history and development of Rhipiphorus smithi with notes on their phylogenetic significance. University of California Publications in Entomology<, 9: 291-314.

Majka, C.G., Chandler, D.S., Sheffield, C.S., and Webster, R.P. 2006. New records of Ripiphoridae (Coleoptera) from the Maritime Provinces of Canada. The Coleopterists Bulletin, 60(4): 299-303.

Many thanks to Zachary Falin of the University of Kansas Natural History Museum for confirming the determination.