Tumculex Mosquitoes

TUMCULEX MOSQUITOES
Order/Family:Diptera/Culicidae           
Scientific Name: Culex spp.

Description: Mosquitoes are members of the order Diptera, i.e., flies.  Mosquitoes are slender, long-legged, two-winged insects 1/8- to 1/4-inch long. Unlike other flies, their wings and bodies are covered with scales, and they have long piercing and sucking mouthparts. Culex mosquitoes have blunt abdomens in contrast to the pointed abdomens of Aedes mosquitoes.

The larvae, or wrigglers, are aquatic with well-developed heads, swollen and unsegmented thoraxes, and eight-segmented abdomens which end in an elongated breathing tube. The pupae, or tumblers, are also aquatic and active. Their heads and thoraxes are encompassed in a large, oval mass with the slender abdomen attached.

The most notable species are the northern and southern house mosquitoes, Culex pipiens and C. quinquefasciatus, respectively, and the encephalitis mosquito, C. tarsalis. The adults of these species are described below:

Northern and southern house mosquitoes are virtually identical in appearance: medium-sized, dull brown to brown-yellow, with even white bands at the end of each abdominal segment.

The encephalitis mosquito is a medium-sized dark mosquito with a white band across the middle of the proboscis (i.e., mouthparts). This characteristic separates it from almost any other Culex mosquito found within the United States.

Biology: Female southern and northern house mosquitoes lay their eggs in rafts which contain from 50 to 200 eggs on the water surface. They hatch within one or two days, completing development within ten days to two weeks. Encephalitis mosquito adults overwinter in protected locations, and, after mating. , lay their eggs in rafts which contain from 200 to 300 eggs on the surface of water. The eggs, which are laid in all types of bodies of water, hatch within two to three days, and, under ideal conditions, complete development within 18 days.

Habits: Southern and northern house mosquitoes prefer to breed in water with high organic matter content and that is contained in artificial containers, such as cans, rain barrels, storm sewer basins, and in ponds and wells. Adults readily enter structures and are vicious biters which feed only at night. They rest within structures during the day, feed extensively on birds, and are the major vector of St. Louis encephalitis and West Nile virus.

The encephalitis mosquito is a common pest west of the Mississippi River, throughout Mexico, and in Canada. It breeds in ponds, canals, burrows, ditches, mud puddles, cess pools, barrels, bird baths, and catchment basins. They enter buildings in search of a blood meal. Although they feed on humans and livestock, they prefer feeding on birds. They are an important carrier of western equine encephalitis, a disease of the nervous system.

In the summer, mosquitoes become major nuisances as they seek out humans for their blood meals. Most service calls result when a customer plans backyard activities, such as an evening party, or at recreational sites, such as golf courses. Perennial problems result from mosquito breeding sites located in inaccessible areas off the customer’s premises, such as salt marshes, swamps, and storage sites and in other sites which are difficult to manage, such as city sewers and beneath structures.

Control: It is important to identify the species causing the problem as well as the breeding site(s). Common methods of collecting mosquitoes for identification are use of light traps, siphoning tubes at resting sites, and dippers to collect larvae. The most effective trap in collecting adult Culex mosquitoes is the CDC gravid trap.  Light traps can be small and portable (CDC) or large and permanently wired (New Jersey). Both styles are designed to catch specimens without destroying them. The effectiveness of night-operated traps can be enhanced by using dry ice or CO2. Adults can be collected by using a siphoning jar trap. The best areas for collection during the day are in shady areas, such as inside or on the shady side of sheds and buildings, sewers, culverts, and drainage pipes.

The collection of larvae is more labor-intensive because it involves investigating potential breeding sites, which may not be accessible, as well as sampling the site in several locations using a dipper. 
Lighting around the property can result in problems with mosquitoes. Because light is a beacon for mosquitoes, the attractiveness of the area should be reduced by locating lights away from the structure and directing them toward it. Sodium vapor and/or yellow bug lights, should be used rather than incandescent or mercury vapor lights.

Regardless of the species, the key to mosquito control is source reduction, i.e., the removal of the water breeding site. For container breeders, this is usually resolved by site clean-up. However, flood water mosquito problems usually require the use of a larvacide. The two most popular larvacides are the insect growth regulator (IGR) methoprene and the bacteria Bti. Liquid, granules, and extended release formulations are available to treat the site even when water is not present. When the product is exposed to water, the active ingredient is released into the water and kills the larvae.
 
Adulticiding with aerosols and ultra low-volume products is effective in killing the mosquitoes within the immediate area but does not provide long term control. Residual spraying of mosquito resting sites also reduces the problem by killing and/or repelling adult mosquitoes.

The use of repellents should be considered. Skin repellents, such as DEET, and clothing repellents which contain permethrin are very effective. At their best, Tiki torches, citronella candles, and similar products offer only temporary relief. Mosquito problems require considerable customer education due to the diversity of species, their often remote breeding sites, and the ability of many species to travel long distances.

To find out more, ask our entymologist, or call us at (301) 570-3900.