RESPONSE OF IPS GRANDICOLLIS (EICHHOFF) ADULTS (COLEOPTERA;SCOLYTIDAE) TO SITES IN BARK INITIATED BY OTHERS OF THE SAME SPECIES

Abstract

Dispersing males and females of Ips grandicollis, whether mated or virgin, initiated galleries on experimental logs held in a naturally infested P. radiara plantation. A few females initiated galleries despite the presence of adjacent male-initiated galleries. Males responded to logs bearing females by entering 41% of the female-initiated galleries. The pattern of entry of these males differed depending on whether the entrance to the female-initiated gallery was blocked by frass or not. The findings of this study has led to interesting speculations about the behaviour and biology of this species.

Biology of the bark beetleIps grandicollis Eichhoff (Coleoptera:Scolytinae) and its arthropod, nematode and microbial associates: a review of management opportunities forAustralia

“…Males usually initiate attack by searching a suitable host and constructing nuptial chambers (a chamber in which a male copulates with females). Ips grandicollis adults are polygamous (Witanachchi ); each male mates with one to seven females, either mated or virgin (Witanachchi ; Witanachchi & Morgan ; Kirkendall ; Garraway ). Females copulate with males in the nuptial chamber and construct brood galleries.…”

“…Males then remove frass from the proximal sections of the galleries and from the nuptial chambers. Eggs are deposited in the individual lateral niches (Witanachchi ) (Fig. b).…”

“…Two different galleries are constructed by solitary females: (1) brood galleries that contain eggs and frass and to which the entrance holes are blocked by frass. These galleries are equal in size to, or slightly larger (100–200 mm) than, galleries constructed by mated females with males (All & Anderson ; Witanachchi ); (2) irregular, winding, 25–75 mm long galleries with no eggs and frass and with clear entrance holes, constructed by virgin females (see Morgan ; All & Anderson ; Witanachchi ). Mated females produce more galleries than virgin females (Witanachchi ).…”

“…These galleries are equal in size to, or slightly larger (100–200 mm) than, galleries constructed by mated females with males (All & Anderson ; Witanachchi ); (2) irregular, winding, 25–75 mm long galleries with no eggs and frass and with clear entrance holes, constructed by virgin females (see Morgan ; All & Anderson ; Witanachchi ). Mated females produce more galleries than virgin females (Witanachchi ). In female constructed galleries, males enter after females, and construct nuptial chambers adjacent to the female galleries or at the base of the galleries of mated or virgin females, respectively (All & Anderson ; Witanachchi ).…”

“…Mated females produce more galleries than virgin females (Witanachchi ). In female constructed galleries, males enter after females, and construct nuptial chambers adjacent to the female galleries or at the base of the galleries of mated or virgin females, respectively (All & Anderson ; Witanachchi ).…”