Flying bark beetles Ips typographus and Pityogenes chalcographus were collected with a portable fraction collector as they arrived at a pipe trap baited with pheromone components. The arrival of beetles through time was not random but rather unevenly distributed (clumped) during a period of constant temperature. Computer simulations of "beetles" flying upwind to pheromone traps under variable "winds" have allowed a deeper understanding of the factors that may cause the nonrandom arrival patterns in nature.

Images © 1996 by John A. Byers, Chemical Ecology.