Row of pipe traps (Norwegian-Swedish drain pipe with funnel) for catching bark beetles attracted to chemicals released from inside pipes. Each pipe has 900 small holes through which bark beetles can crawl and then slip eventually into a small bottle at the bottom of the tube. Other beetles can strike the cylinder and drop through the funnel into a second bottle. In this way, differences in male and female behavior can be indicated if there is a significant difference in the sex ratio.

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