MUTUAL INHIBITION OF THE ATTRACTANT PHEROMONE RESPONSE BY TWO SPECIES OF Ips (COLEOPTERA: SCOLYTIDAE)

The bark beetles, Ips pini and I. paraconfusus, are not cross-attractive in the field although they attack the same host material at the same time. Logs containing the pheromone-producing sex (males) of both species side by side attract significantly fewer beetles of each species than do males of either species alone. Ipsenol, a component of the male I. paraconfusus pheromone, duplicates the activity of male I. paraconfusus in inhibiting the response of I. pini to male I. pini. Linalool from male I. pini also reduces the catch of I. paraconfusus in response to male I. paraconfusus. Simultaneous production of a specific attractant pheromone and an interspecific chemical inhibitor favors exclusive use of the host substrate by the first arriving species.