In a previous post, I discussed the development of the Hartstack Wire Cone Trap for monitoring cotton bollworm populations. Traps require a lot of thought and observation of insect biology to be effective and useful.
The Lindgren Funnel Trap is an important trap for monitoring bark beetles and other beetles in forested areas. The Lindgren Funnel Trap was the brainchild of BS Lindgren who first published his trap design in 1983 while working for the Canadian Forest Service.The 1970s was a decade that ushered in large numbers of new insect pheromone identifications. Scientists were experimenting with pheromones for use in monitoring and attempts to control populations by trapping a large percentage of the population. In the early 1980s, Sweden was experimenting with the deployment of large numbers of traps to reduce populations of a tree destroying bark beetle, Ips typographus. The Swedish traps were constructed from 4 inch diameter drainage pipe. The black pipes were about 2 meters in length and designed to resemble a tree trunk. The pipe contained numerous holes to allow the beetles easy access to the interior. The idea behind the trap was to attract the bark beetles to the trap with pheromones. The beetles would land on the outside, enter the trap through the holes and plunge to their death into a container connected to the bottom of the pipe with liquid that would drown or kill the beetles.
The traps captured a lot of beetles, but not enough to control them. They were useful for monitoring but were unwieldy to carry into the forest. Biological observations of beetles attracted to the trap suggested that the trap was not very efficient. Many more beetles landed on the outside of the trap than entered through the holes.
Lindgren replaced the solid black pipe with a series of funnels loosely connected together. The funnels telescope inside each other to create a compact trap much easier to transport and store than the unwieldy pipes. When hung from its wire, the trap extends into an elongated series of funnels. Instead of tiny entrance holes in the sides of a straight pipe, the Lindgren funnels have sides that slope in toward the middle. Beetles flying toward the trap collide with the side of any of the several funnels. The collision knocks the beetle out of the air and it falls onto the funnel below. The beetle slides down the sloping sides of the funnel and plunges into the container at the bottom.
Today, the Lindgren Funnel Trap is commercially sold and standardizes insect monitoring in forested areas.