Brood Development of an Inbreeding Spermatophagous Scolytid Beetle, Coccotrypes graniceps (EICHHOFF) (Coleoptera : Scolytidae)

Brood development of an inbreeding spermatophagous scolytid beetle, Coccotrypes graniceps, was observed in the laboratory. When overwintering females were inoculated into an acorn of Lithocarpus edulis, both males and females emerged simultaneously and the foundresses left their acorns soon after emergence of their offspring. The female progeny laid eggs and then some of them left their birth acorns following the foundresses but no males went away. The sex ratios were highly biased toward the female in broods produced by both overwintering females and their female progeny. In the case of inoculation of virgin females, a few eggs were laid and only males were produced. These foundresses did not left their acorns and laid eggs again after emergence of their son as adults. The second brood was also highly biased toward the female. It was obvious that the virgin foundresses copulated with their male progeny and that the sex determination of this species was a haplo-diploid type.