The Society for the study of flies (Diptera)

Another method of finding flies in winter, in particular early in the year, is to use a suction sampler in large tussocks. This enables you to find many overwintering insects, in particular flies and beetles.

A suction sampler is a converted leaf blower, by using the suction funtion, but fix a net bag over the tube. This means that the flies etc get caught in the net bag and can then be taken out by using a pooter. Care must be taken that the net bag does not get sucted into the motor.

Good luck.