Midges By The Millions

One morning I came into my office and found piles of tiny green gnats on the floor next to some exit doors. There were gnats all over my desk, on the book shelves, everywhere on the floor, and in clumps in the plastic covers beneath the fluorescent ceiling lights. I quickly recognized these as simply midges, and midges in the fly Family Chironomidae to be specific. Why were they suddenly in my office? Well, these kinds of midges are subject to sudden population outbursts. They breed as larvae in water, and several water sources were nearby. The adult insects, the gnats, are attracted to lights at night, and on the outside they were drawn to security lights and lights over the doors, and once inside were attracted to the lighted “Exit” signs. A visit the evening before by our cleaning service, and doors likely propped open while they worked on this warm evening, allowed the midges to enter the office without any problem.


These midges were very small, but other species in this group are much larger and strongly resemble mosquitoes. However, there are some noticeable differences that will help you separate mosquitoes from midges, and reduce your concerns that these flies will bite you. First, the midges do not have that piercing beak, or “proboscis”, that mosquitoes use to suck blood. The mouthparts of the midge are tiny, and in some species are not even functional, leading to a very short life for the adult midge. Second, most of the Chironomid midges have feather-like antennae, while the biting female mosquitoes have narrow antennae. Third, most of these midges lay more or less flattened on the walls, with their wings held flat over the abdomen and their legs out to the sides. Mosquitoes tend to rest in a more elevated stance.


Another similarity between midges and mosquitoes is their breeding sites, or the habitat in which the larva stage develops. We are all aware that mosquitoes must have standing water in which to develop, and so it is with midges. However, the larva of the midge will often live down at the bottom, nestled in the muck and mud found there and feeding on algae and organic matter found there. Other kinds may be found higher in the water environment, and midges develop in nearly any kind of aquatic environment, including streams, ponds, lakes, drainage ditches, and even in heavily polluted sewage water. They are not harmful in any way, other than the nuisance of having large numbers of them around you, and in turn serve as an important food resource for many other animals.

The species that live in the substrate at the bottom of ponds or rivers are called “Blood Worms”, due to the bright pinkish or red color they develop as they mature. The color is due to a high level of haemoglobin in their blood, needed for better transport of oxygen in their oxygen-poor habitat. While they may be a serious nuisance when swarms of the adults annoy us, the larval stage is highly beneficial as they consume waste materials and recycle them.  

Midges breed and develop quickly, and may have many generations in a single season, with swarms of the adult midges appearing almost every night. They are strongly attracted to lights at night, and this can offer some interesting and slightly amusing events. Nearly every year we hear of massive swarms of midges descending upon a baseball field during a nighttime game, surrounding players on the field and drifting into the stands. The bright lights illuminating the playing field were the draw, and when that baseball field is near some large body of water, such as the Great Lakes, an equally large number of the midges can make themselves known and hated.  

Sometimes certain places will have an ongoing and chronic problem with midges, such as the Clear Lake Gnat around Clear Lake in northern California. Although it is in a different family called the Chaoboridae, this large gnat is similar to the Chironomid midges in appearance, but is a very large midge. Due to ongoing control programs the problem today is not what it used to be, where in the past such massive outbreaks of this gnat were so thick it was difficult to breathe outdoors without inhaling a few of them, and outside walls of homes might nearly be covered with tens of thousands of the gnats.  

Controlling this nuisance caused by the midges may not be easy. Fly control in general relies heavily on eliminating the source, meaning the larvae that develop to the flying adult stage. Since the larvae are living in water you either need to drain that water or treat it in some legal manner. Draining is often impossible, due to environmental concerns or just the fact that it is a permanent flowing river or lake. Chemical applications should definitely be left to a licensed professional. However, you can take steps to reduce the problem around your own home. First, of course, is to do what you can to keep them from being attracted to your home as the winged adult. Since they are being drawn to lights at night you can:
  • Keep outside lights turned off at night during swarming season.
  • Change white lights to yellow bulbs that are much less attractive to night-flying insects.
  • Place needed outside lights away from doorways.
  • Keep doors closed and windows tightly screened to exclude the midges, and use curtains or blinds to shield windows from indoor lights.
  • Use predatory fish in the breeding sites to feed on the larvae. These fish may be readily available from your regional Mosquito and Vector Control Agency.