Flight muscle volume change in Ips confusus (Coleoptera: Scolytidae)

Abstract

Three pairs of dorsal–ventral flight muscles were excised from Ips confusus adults and measured, and their volumes calculated. There was a progressive development of muscle tissue from callow to emerged brood adults followed by a rapid degeneration (often over 90% of the original volume) after the insects entered fresh host logs. Solitary individuals of each sex forced to attack logs underwent muscle degeneration within 3 to 4 days. However, greater degeneration occurred when both sexes were in the same gallery and allowed to mate. Before reemergence, the flight muscles or males gradually increased in size whereas those of females remained degenerate much longer before rapidly regenerating. This condition was correlated with the longer reproductive period in females. The muscle volumes in reemerged adults of both sexes were larger than those of any other stage, possibly implying selection of superior insects.