Malaise traps
Malaise traps are like open-walled tents. Insects that fly into them hit the dark-coloured central panel and are drawn by phototactic response to move upward into the light-coloured roof and into the collecting chamber positioned at the uppermost peak. We have used them for a wide range of studies as they produce large catches of a wide range of flying insects, and certainly provided the greatest diversity per trap unit of any of the traps trialled here.
They are especially useful for flies and wasps, but also very effective for moths and beetles. A number of other crawling invertebrates invariably get caught as well, including spiders, ground weta, and cockroaches.
Malaise traps are available in a wide range of designs, but the net design we standardised was that described by Townes (1972). Similarly, a number of methods of poling out the Malaise traps have been described, or they have simply been hung from trees and guyed out with ropes. We use aluminium poles arranged in a t-shape at each end to maintain the shape of the nets, and these are guyed out with strong cord. The base of the net is always pegged into the ground. The nets are oriented with the collection bottle towards the North to maximise the phototactic response. A range of collection fluids have been suggested for Malaise traps, and each has merits in particular circumstances. We have tried 70% ethyl alcohol, Gault’s solution, and 30% monopropylene glycol in our Malaise traps without any obvious reductions in catch.
The disadvantages of Malaise traps are that they are large, expensive (relative to some other traps), and highly visible pieces of equipment, so are not generally suitable in situations where public interference and vandalism are a likely problem. They are also readily damaged in high winds, so are generally unsuitable for exposed situations. They can be time consuming to put up (especially by yourself), and need a relatively large, clear area, which can be difficult to find in some situations. See our discussion of a mini-Malaise trap we designed to allow Malaise trapping in difficult circumstances.
Reference
Townes, H. 1972. A light-weight Malaise trap. Entomological News 83: 239-247.