Window traps
Many designs of window traps are available. They work on the principle of insects flying into them and then falling into a collection container containing a preservative. Some versions can also have a collecting unit fitted on the top to collect those invertebrates that move upwards instead. The units we have used consist of two clear perspex (acrylic) panels with notches cut out so they sit perpendicular to each other to trap insects flying from any direction. The bases and tops are cut to angles so they fit perfectly into large (220 mm diameter) kitchen funnels that lead into collecting bottles. Our design has the bottom funnel on a tripod of sturdy aluminium legs, and the top is held on with two elastic cords which hook into the bottom funnel.
Window traps collect a wide range of flying insects, but are particularly effective for beetles, which tend to hit a barrier and drop. Flies, wasps, and bees are also caught in good numbers, along with moths and some bugs. The addition of a small strip of colour to the centre of the panels does appear to increase the effectiveness of the trap for certain species by attracting them to do a fly-by investigation. We tried a strip of yellow electrical tape and noticed a marked increase in the catch of honeybees. Trials are needed to determine how different colour strips might affect the catch. Odour attractants could also be used.
Window traps are relatively quick to put out, and quick and easy to service in the field. They take up less room than a Malaise trap and are less expensive, but they are still a noticeable trap, so may not be appropriate in areas where human interference is a likely problem.