Date of Award
Master of Science
Arthropod predators are able to influence the population dynamics of forest insects such as bark beetles. Two common predators of bark beetles are Temnochila virescens (F.) (Coleoptera: Trogositidae) and Thanasimus dubius (F.) (Coleoptera: Cleridae). Studies on T. virescens ecology have been few and not quantitative. Also, in recent years there has been increased focus on multiple-predator effects on the population dynamics of a single prey species, which better describes a natural system. Therefore, a series of three studies was conducted to provide a general overview of T. virescens ecology and its potential use for biological control. The first study examined the functional response of T. virescens toward its Ips prey. The second evaluated the impacts of intraguild competition between T. virescens and T. dubius adults on predation of a mutual prey species, I. grandicollis. The third determined if there were differences in pheromone preference among individual T. virescens adults. To evaluate the functional response, T. virescens and Ips grandicollis (Eichhoff) adults were combined in varying densities. Ips grandicollis survival was assessed by examining the number of prey eaten in relation to predator and prey densities. I found that a type II functional response model incorporating interference provided a good fit for the data. The interference was strong enough that a ratio-dependent model fit the data just as well as the full model. The effect of competition between T. dubius and T. virescens adults on I. grandicollis survival was determined by placing varying numbers of each predator with a set prey number. I found a significant interaction between densities of the two predators, which indicates possible emergent predator effects. The combined effect of the predators was risk reducing for prey, likely because of intraguild predation. The predator T. dubius alone was more efficient at reducing the number of prey adults successfully entering the log. This study indicates the importance of low density releases of these predators for augmentative biological control, to reduce the effects of intraspecific competition. To determine if there were differences in pheromone preference among individual T. virescens adults, a mark-release-recapture experiment was combined in the field to provide a choice test between ipsenol and ipsdienol pheromones. Temnochila virescens adults that were initially captured on ipsenol were more frequently recaptured with this pheromone, while those first captured on ipsdienol were recaptured on both pheromones. This suggests populations of T. virescens are composed of specialists attracted only to ipsenol and generalists attracted to both ipsdienol and ipsenol pheromones.
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