Slow-rotating pair of sticky-traps. The trap arms (metal poles) are supported by guy wires from the center pole which is mechanically rotated by a gear driven motor and flashlight batteries (constant voltage regulated at 12 volts). I believe this invention of mine will be very important to further progress in discriminating differences in pheromone blends and subtle effects of pheromone components. The idea is to rotate a pair of traps (which can be sticky or barrier type) very slowly at about 1 revolution per 30 minutes. The traps in this case were 6 meters apart so at this rotation speed a trap would travel at about (3.141593*6/30) or 0.63 m/min (or about 1 cm per second). This means that they are essentially stationary when the bark beetle tries to land (they fly at 2 m/sec but less when landing) after being attracted by pheromone. The advantage of this type of trap system is that random variations due to trap position are evened out, in contrast to all other methods where traps are stationary for a period of several hours to a day and then moved at random to new positions. The rotation of traps, since all positions are used should allow more powerful Chi-Square statistics and thus more discriminatory tests.
Two papers which report some results using the slow mechanical rotation of trap pairs are Byers et al. (1990) and Byers (1993) . I prefer this system and now use 3 or 4 of them each spring. The problem is that the system is awkward and costly compared to a very simple trap, but then many more simple traps are needed to achieve the same results in my opinion. Jörgen Jönsson helped me with advice on construction and design of the trap rotor.

Images © 1996 by John A. Byers, Chemical Ecology. This photo of me was taken by Erling Jirle while I was doing field research in Denmark.