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Midges

 

 

 

 
Midge Life Cycle

 
What They Are and What To Do About Them

Midges are small flying insects that closely resemble mosquitoes. Alameda County Mosquito Abatement District is aware that midges are emerging in large numbers in areas of the county that are near channels, creeks and large bodies of water. These insects pose no threat to pets or people and are an important part of the food chain for local and migratory waterfowl. These insects are highly attracted to lights and "Bug Zappers". Minimizing the use of outside lights will help to reduce their presence near your home. Should you choose to use a "Bug Zapper", keep it as far away from your residence as possible to maximize its effectiveness.

Male midges form large swarms when temperature, humidity, and light conditions are right for their species. Different species swarm under different environmental conditions and usually only during a specific time of the day. When more than one type of midge is present in a neighborhood, there may be the appearance of having swarms all of the time. Adult midges are short lived, their function merely to swarm, mate, and lay their eggs. A diagram of the midge life cycle can be seen at the top of this page. Adult midges can be easily identified by the flattened, almost smashed appearance they have when resting on any surface. Other midge-like insects and mosquitoes appear to be standing on the ends of their legs, with their bodies clearly not touching the substrate they are resting on.

Although midges do not bite, they often occur in large numbers and can be annoying. The following suggestions may help minimize their annoying presence:

Commonly encountered Midges

Dicrotendipes modestus

Larvae can occur in brackish water, are commonly found on the surface of aquatic vegetation and among or on vegetation found on rocks, logs and similar substrata. Larvae construct silken tubes on the substrate and the pupal stage is also spent in the tube. Can occur on bottom mud but as submerged vegetation increases larvae will become more prevalent on the vegetation. Larvae of this midge are commonly associated with Myriophyllum (Watermilfoil and Parrotfeather) and Typha (Cat-Tails). It is probable that larvae are also found in and on algal mats. Larvae feed on algae, detritus and small microorganisms in the water. Adults of Dicrotendipes spp. have been considered pests due to large emergences.

Chironomus decorus

Larvae, also known as blood worms, are filter feeders that construct mud tubes on the bottoms of lakes, ponds and streams and prefer oxygen deficient waters. Microorganisms and detritus are their primary food sources. This midge can produce up to five generations per year in warmer climates, especially if found in the shallower parts of oxygen deficient bodies of water. This fly has been found breeding in sewage oxidation ponds.

Chironomus plumosus

This is the largest midge in North America and is found throughout the continent. Larvae, commonly known as blood worms, are usually reddish in color and are found in the muddy bottoms of large rivers, gravel pits and eutrophic lakes. The immature stages inhabit tubes constructed of small particles and can be found at depths varying from 6 to 20 meters. The feeding habits for the larvae of this midge is very similar to Chironomus decorus (see above).Adults occur year round but are most abundant during late spring to early summer.

Orthocladius mallochi

Larvae of the Orthocladiinae prefer the cold waters of lakes, rivers and streams and live on or in plants. Adults of O. mallochi have been collected from December through May in California. Larvae have been found in 83 degree pools in the Palm Desert area of southern California and in small moving streams of southern Santa Clara County. Specimens of this midge have also been collected in Shasta, Fresno and Riverside Counties. The number of generations per year is not clear since this midge has been confused with similar looking species in the past. Similar taxa vary from univoltine to multivoltine depending on habitat and locale.
 

Comparing Midges to Mosquitoes