Finding and identifying flies

Finding flies

There are many ways to find and record flies. You can for example patiently watch a flower or suitable basking spot and see what comes, you can carefully stalk them with a net, or you can sweep a hand net back and forth through the vegetation. The last method is often very productive, allowing you to find flies you would be fortunate to see or catch otherwise. 

Or you may choose to use some sort of trap. There are various types of flight intervention traps, like Malaise traps, which can be very effective. Emergence traps, effectively netted domes or tents places over the ground, rotting wood or so forth, can tell you where larvae are developing.

A Dipterist’s Handbook will tell you much more about ways of finding flies, and where best to look for them.

How to identify flies

Using microscopes to identify flies (photo by Judy Webb)

There are now many resources available to help you identify flies. Superb books have been published on the identification (and biology) of hoverflies and soldierflies (and allies), and keys are available for the adults of most families. In addition, there are some excellent websites available, including the forums on this site where experts willingly provide advice. 

Members of Dipterists Forum also have access to a range of keys which are as yet unpublished or which are being tested and on which feedback would be welcomed - if you are a member and are logged in to this website you will see this page under the "Resources" menu. If you are not yet a member you are very welcome to join us.

If you are starting out, or wishing to get to grips with one family, then we recommend you attend one of the workshops organised by the society or by other organisations. See News and Events for details

With practice a range of flies can be confidently identified in the field, in the net, or from photographs.  However many more require examination under the microscope. This means they have to be killed.  Provided no more specimens are taken than is necessary for identification and recording it is very unlikely there will be any adverse impact on populations. A pair of swifts can catch up to 20,000 insects for their brood in a single day! The likely benefits to conservation from taking specimens to identify outweigh the risks to the species (provided records are made and submitted to accessible databases). Nevertheless, rare or threatened species that can be identified while alive should never be killed, but, if caught, released back as soon as possible where they were found.