Flies around the house don’t have to be UFOs

A long time ago when I was a college student, I worked part-time in a genetics lab. The organism of choice for these experiments was the lowly Drosophila melanogaster – our very common fruit fly. They were excellent subjects because their genetics were simpler than mammals’, they were small and, therefore, easily handled and large populations could be kept in small bottles. With a rapid generation time  - their life cycle can be completed in two weeks – mutations could be easily followed for many generations. Today, for me, fruit flies are simply a minor nuisance in the kitchen brought in on summer fruit or bananas. 

Our home is among those Riverdale households that received the brown organic recycling can from the Department of Sanitation and I have been dutifully placing all my kitchen organic waste into it. While approving wholeheartedly of the concept, I have not enjoyed the smelly mess that remained after garbage pickup. Therefore I was extremely pleased to receive an email this week from the department that they have approved the use of clear plastic bags to line the cans. These bags will be removed from the cans with their load of garbage and removed later by Sanitation. This change in regulations can improve clean up enormously and I am personally very grateful.

Meanwhile, several weeks ago I was outside preparing to clean the recycling can out and it suddenly dawned on me that there were many small, brown cocoons attached to the lid of the can and numerous larvae crawling around inside the can. With my background dealing with Drosophila, I thought it would be interesting to hatch out the insects and isolate the adult flies, which I assumed would be my old friends the fruit flies. I took a glass jar, placed some vegetable peelings in it, made holes in the lid and lifted 20 larvae off the can and placed them inside the jar. I examined the jar every day and about twelve days later, I had a whole group of flies crawling up the sides of the jar. They were small and looked similar to fruit flies but I always like to consult with an expert before stating something categorically. Fortunately, I have an acquaintance who is an entomologist, but like so many professionals, he has his particular area of expertise and he is most familiar with pests affecting crops. He did, however, voice some skepticism saying that he could not confidently identify them as Drosophila. In addition, I was researching this further and remembered that fruit flies have red eyes and my specimens did not.

At that point, I turned to the Department of Sanitation, assuming they must have entomologists on staff who would be familiar not only with such questions but with pests that are commonly found in garbage. They were very accessible but demurred on an identification until I could send them a photo. In the lab we used ether to anesthetize our flies and clearly I had no such tools at present. They gave me several good suggestions as to how to isolate a fly in order to photograph it.  With a decent photograph finally in hand, I finally received an answer. These are, indeed, not fruit flies but phorid flies – otherwise known as humpbacked flies. 

While probably not completely exhaustive, there seem to be four types of small flies that one can encounter around the home. They are the fruit flies and the phorid flies mentioned so far. In addition, there are drain flies and sphaerocerid flies. While all of these flies scientifically placed in the Oder Diptera, they all belong to different  families. Drosophila are Drosophilidae, the phorid flies are  Phoridae, the drain flies which look moth-like and are called moth flies are in the family Psychodidae, and finally the sphaerocerid flies are in the family Sphaeroceridae. The other commonality is that they are all found in damp areas with rotting vegetation, garbage or sewage. For homeowners the most important question is how to get rid of them. Careful cleaning is always the first step. After that, the Internet is full of solutions – some of which I have found useful.  Fruit flies have been called vinegar flies since they cannot resist cider vinegar. A commonly suggested way of ridding your kitchen of them involves covering a partially full bottle of cider vinegar with secured plastic wrap, poking a small hole in the plastic. The flies enter and cannot exit. 

Hatching your own flies might not be as intriguing as hatching butterflies but it makes a good experiment to do with children.