Malaise Traps

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The Malaise trap is a type of flight interception trap resembling a small tent. It takes its name from the Swedish entomologist Rene Malaise who is said to have invented the trap when he noticed, on returning from a day's collecting, that his tent contained more insects than he had caught. Anyone who has camped will have experienced the principle observed by Malaise, that insects trapped within the tent will ascend and seek a means of escape at the apex of the roof. The Malaise trap is designed to take advantage of this inate behaviour of many insects. Since Malaise's original design, modifications to it have been suggested most notably by the American hymenopterist, Henry Townes.

A Malaise trap is basically an open-sided tent and comprises a central baffle, two end walls, a sloping roof and most importantly a collecting head. The collecting head on the B&S Malaise trap consists of a plastic coated metal frame holding a plastic bottle. Insects enter this bottle from the net and drop down into a second, detachable, bottle. A hose or jubliee clip is used to join the trap to the net. The collecting head is placed at the apex of the roof where the baffle and the upward sloping roof direct the insects.

Malaise traps are particularly suited for catching Diptera and Hymenoptera; insects of both these orders ascend when they hit a barrier. Coleoptera conversely descend when they encounter a barrier. Placing two water traps on the ground on each side of the central baffle will catch these insects.

The standard Malaise trap has just one collecting head. A modification has a complete central baffle with two collecting heads, one for each side. This type of trap allows one to investigate differences in the insects arriving from opposite directions. This might for example be used to investigate migrating species.

Siting of traps
The success of Malaise traps will depend on many factors. It is generally best to site the trap at right angles to natural flight lines. Good places include woodland rides and tracks, the edges of woods, the boundary of two habitats, along hedges or across watercourses. Shelter is also important as strong winds will reduce the efficiency of the trap and may damage the net. It is also best to avoid areas used by domestic and wild mammals as the trap will undoubtedly attract their attention.

Bycatch
Malaise traps are an efficient method of remote sampling insect faunas. They can be used to investigate whole faunas or just single taxa. However as they are indiscriminate, catches contain much more than the target taxa. This material is unfortunately often just discarded in the absence of anyone to work on it - potentially a great waste of effort and material. We feel this material may be used if researchers were aware of where Malaise traps were in operation. Researchers using Malaise traps can register their project with us. These details will then be placed on our website, so that other researchers can make contact and make use of offered material.