LIFE-HISTORY AND ECOLOGY OF PLAGITHMYSUS-BILINEATUS, (COLEOPTERA, CERAMBYCIDAE) AN ENDEMIC HAWAIIAN BORER ASSOCIATED WITH OHIA LEHUA (MYRTACEAE)

Host selection-oviposition by P. bilineatus Sharp on its single host, M. collina (Forst.) Gray polymorpha (Gaud.) Rock, was a response to damaged or stressed hosts. Larval survival was not significantly higher in stressed hosts, but the number of galleries per host increased as the vigor (crown foliage condition) of the host decreased. Of 34 larvae implanted in healthy hosts, only 4 completed development; initial decline symptoms in these hosts did not appear until 10-22 mo. after adult emergence. Artificially girdled trees were monitored for 3 yr, by which time 4 girdled trees had died, 3 being heavily attacked by P. bilineatus and 1 by ambrosia beetles. Harley diet with Bacto-Peptone supplement was tested as a culture medium for P. bilineatus larvae, with moderate (66%) success. The ecological functions of P. bilineatus were considered relative to the extensive decline of hosts in rain forests on the island of Hawaii.