A Cologne That Spells Trouble

If wearing male cologne seems outre, consider the social risks of the pine engraver beetle, studied by biology graduate student Alice Shumate. Ips pini males burrow in the bark of pine trees and release pheromones to attract females but also alerting the predatory clerid beetle Thanasimus dubius to their presence.

The pine engraver beetle has developed its own version of safe sex: it produces a variety of pheromone blends to confuse and elude the local T. dubius. Unfortunately, the predator likes more than one pheromone. As clerid beetles thin out the population of engravers that use a particular blend, engravers genetically inclined to other blends become more common. T. dubius eventually picks up on this shift and changes its preference to the new popular blend.

The evolutionary basis for this chemical cat-and-mouse game is poorly understood, but Shumate hopes to change that. Working with biology professor Matt Ayres, she believes that I. pini and T. dubius may represent a classic example of coevolution—a system where the prey exerts selective pressure on the predator as well as vice versa. Because it is rarely possible to study evolutionary interactions between predator and prey in a natural system, Shumate and Ayres expect to contribute valuable empirical data to a field of biology dominated by theory.

Tree farmers will be interested in the results for another reason. In Wisconsin alone, engraver beetles damage more than $5 million worth of pine crops every year. Abetter understanding of the engraver's pheromone biology should help landowners and forest managers predict the insect's response to suppression programs, logging activity, and ecological changes.

The pine engraver practices safe sex.