The effects of host switching upon two species of Ips bark beetles (Coleoptera: Scolytidae) and their insectan associates

Increasing levels of global trade and travel result in the accidental introduction of exotic organisms to new environments. A number of these introductions results in the establishment of 'new associations' between pestiferous organisms and novel hosts. When these 'new associations' result in an ecological imbalance, biological control is one avenue of redress through the introduction of natural enemies. Most successful examples of biological control have used natural enemies from the regional origin of the pest organism, but when both the pest and the host are exotic species, is it better to look for potential biological control agents in the origin of the host or pest?; The complex physical geography of California has resulted in a number of insular environments. Pine forests occur in the coastal foothills as well as in the Sierra Nevada, but due to the distances between these two environments, each locale has different native pine species as well as insect associates. In both of these locales the native pines are attacked by bark beetles (Coleoptera: Scolytidae) in the genus Ips. By artificially switching host pine species and the different associated Ips bark beetles, a number of 'new associations' between host pine trees and Ips bark beetles can be observed.; The 'new associations' reveal information not only about the host pines and the bark beetle, but also about the natural enemies of the bark beetles. The response of a number of predators and parasites to 'new associations' were examined in the field to determine what were the most important factors with regards to location and acceptance of prey. The importance of the host tree substrate was illustrated as this factor often proved to be the most critical with regards to host acceptance.