Mosquitoes in Your Life
Donald J. Sutherland, Research Professor in Entomology
Wayne J. Crans, Associate Research Professor in Entomology
In each state, there are many kinds of mosquitoes. New, Jersey has sixty species, each of which has a different habitat, behavior and preferred source of blood. About ten of these species are so numerous, and such vicious biters of man and animals in the state, that many years ago, most New Jersey counties established agencies to control mosquitoes. Organized mosquito control is necessary because mosquitoes are not only a nuisance as biting insects, but are also involved periodically in transmitting disease to humans and animals.
Mosquito control agencies reduce mosquito populations in various ways, including water management, biological control agents, and insecticides, which can be effective in controlling mosquito larvae (larvicides) or mosquito adults (adulticides). Mosquito populations can increase rapidly, and, depending on flooding and general weather conditions, mosquito control agencies cannot always keep up with mosquito problems in all areas. Very often, residents can help significantly by controlling mosquitoes around their homes and properties.
This booklet explains the general biology and significance of mosquitoes and tells what the public can do to reduce mosquito problems.
Mosquitoes Need Water: All mosquitoes have four stages of development-egg, larva, pupa, and adult-and spend their larval and pupal stages in water. The females of some mosquito species deposit eggs on moist surfaces, such as mud or fallen leaves, that may be near water but dry. Later, rain or high tides reflood these surfaces and stimulate the eggs to hatch into larvae. The females of other species deposit their eggs directly on the surface of still water in such places as ditches, street catch basins, tire tracks, streams that are drying up, and fields or excavations that hold water for some time. This water is often stagnant and close to the home in discarded tires, ornamental pools, unused wading and swimming pools, tin cans, bird baths, plant saucers, and even gutters and flat roofs. The eggs deposited on such waters soon hatch into larvae. In the hot summer months, larvae grow rapidly, become pupae, and emerge one week later as flying adult mosquitoes. A few important spring species have only one generation per year. However, most species have many generations per year, and their rapid increase in numbers becomes a problem.
Only the Female Can Bite: When adult mosquitoes emerge from the aquatic stages, they mate, and the female seeks a blood meal to obtain the protein necessary for the development of her eggs. The females of a few species may produce a first batch of eggs without this first blood meal. After a blood meal is digested and the eggs are laid, the female mosquito again seeks a blood meal to produce a second batch of eggs. Depending on her stamina and the weather, she may repeat this process many times without mating again. The male mosquito does not take a blood meal, but may feed on plant nectar. He lives for only a short time after mating.
Winter Survival Is Important: Most mosquito species survive the ,inter, or overwinter, in the egg stage, awaiting the spring thaw, when waters warm and the eggs hatch. A few important species spend the winter as adult, mated females, resting in protected, cool locations, such as cellars, sewers, crawl spaces, and well pits. With warm spring days, these females seek a blood meal and begin the cycle again. Only a few species can overwinter as larvae.
Mosquitoes Can Transmit Disease: Mosquito-borne diseases, such as malaria and yellow fever, have plagued civilization for thousands of years. Organized mosquito control in the United States has greatly reduced the incidence of these diseases. However, there are still a few diseases that mosquitoes in New, Jersey can transmit, including Eastern Equine Encephalitis and St. Louis Encephalitis. The frequency and extent of these diseases depend on a complex series of factors.
Mosquito control agencies and health departments cooperate in being aware of these factors and reducing the chance of disease. It is important to recognize that young adult female mosquitoes taking their first blood meal do not transmit diseases. It is instead the older female, ho, if she has picked up a disease organism in her first blood meal, can then transmit the disease during the second blood meal. This is also true for the mosquito transmitted disease in dogs, dog heartworm (a mosquito-borne disease), which is explained in Circular 607-A, " Does Your Dog Have Heartworm ?" (available from the New, Jersey Agricultural Experiment Station).
You Can Reduce Mosquito Annoyance: When mosquitoes are numerous and interfere with living, recreation, and work, you can se the various measures described in the following paragraphs to reduce their annoyance, depending on location and conditions.
Reduce the Amount of Standing Water: The most efficient method of controlling mosquitoes is by reducing the availability of water suitable for larval and pupal growth. Large lakes, ponds, and streams that have waves, contain mosquito-eating fish, and lack aquatic vegetation around their edges do not contain mosquitoes; mosquitoes thrive in smaller bodies of water in protected places. Examine your home and neighborhood and take the following precautions:
- Dispose of unwanted tin cans and tires.
- Clean clogged roof gutters and drain flat roofs.
- Flush sump-pump pits weekly.
- Stock ornamental pools with fish.
- Change water in birdbaths, fountains, and troughs twice a week.
- Clean and chlorinate swimming pools; when not regularly used, they should be emptied.
- Turn over unused wading pools and other containers that tend to collect rainwater.
- Cover containers tightly with window screen or plastic when storing rainwater for garden use during drought periods.
If mosquito breeding is extensive in such areas as woodland pools or roadside ditches, the problem may be too great for individual residents. In such cases, call the organized mosquito control agency in your area. These agencies have highly trained personnel who can deal with the problem effectively.
Use Insecticides Safely: Several commercially available insecticides can be effective in controlling larval and adult mosquitoes. These chemicals are considered sufficiently safe for use by the public. Select a product whose label states that the material is effective against mosquito larvae or adults. For safe and effective use, follow the instructions for applying the material. The label lists those insects that the Environmental Protection Agency (EPA) agrees are effectively controlled by the product. Read the label.
For use against adult mosquitoes, some liquid insecticides can be mixed according to direction and sprayed lightly on building foundations, hedges, low shrubbery, ground covers, and grasses. Do not overapply liquid insecticides - excess spray dips from the sprayed surfaces to the ground, here it is ineffective. The purpose of such sprays is to leave a fine deposit of insecticide on surfaces where mosquitoes rest. Such sprays are not effective for more than one or two days.
Some insecticides are available as premixed products or aerosol cans. These devices spray the insecticide as very small aerosol droplets that remain floating in the air and hit the flying mosquitoes. Apply the sprays upwind, so the droplets drift through the area here mosquito control is desired. Rather than applying too much of these aerosols initially, it is more practical to apply them briefly but periodically, thereby eliminating those mosquitoes that recently flew into the area.
Repellents Can Offer Relief: Various commercially available repellents can be purchased as creams, lotions, or in pressurized cans and applied to the skin and clothing. Some manufacturers also offer clothing impregnated with repellents; coarse, repellent-bearing particles to be scattered on the ground; and candles whose wicks can be lit to release a repellent chemical. The effectiveness of all repellents varies from location to location, from person to person, and from mosquito to mosquito. Repellents can be especially effective in recreation areas, where mosquito control may not be conducted. All repellents should be used according to instruction. A further discussion of insect repellents is offered in Circular 592-A, New Jersey Agricultural Experiment Station.
What Attracts Mosquitoes?: Mosquitoes are attracted by perspiration, warmth, body odor, carbon dioxide, and light. Mosquito control agencies use some of these attractants to help determine the relative number of adult mosquitoes in an area. Several devices are sold that are supposed to attract, trap, and destroy mosquitoes and other flying insects. However, if these devices are attractive to mosquitoes, they probably attract more mosquitoes into the area and may, therefore, increase rather than decrease mosquito annoyance.
You Can Learn More about Mosquitoes: Much has been published and is available in libraries about mosquitoes and their effect on mankind. But you can also learn a great deal by watching mosquito larvae, pupae, and adults. Most larvae and pupae come to the water's surface to get oxygen and can be captured by dipping the surface of the water with a cup. Sometimes, the larvae and pupae are quicker than the hand and dive to avoid capture. Once caught, however, they can be confined in a small dish of water, and studied for their type, behavior, growth, and structure. The adult mosquito can best be captured in the act of biting by inverting a vial or small jar over her. When disturbed, she will fly up into the container, which can then be quickly capped. A short time in the freezer will immobilize the adult for closer examination. The following chart shows some of the principal characteristics used to identify three major genera of mosquitoes.
Some Suggested References
- Darsie, R. F., Jr., and R. A. Ward. 1981. Identification and Geographical Distribution of Mosquitoes of North America, north of Mexico. Fresno, CA: American Mosquito Control Association.
- Headlee, T. J. 1945. The Mosquitoes of New Jersey and Their Control. New Brunswick, NJ: Rutgers University Press.
- Journal of the American Mosquito Control Association, formerly, Mosquito News
- Mattingly, P. F. 1969. The Biology of Mosquito-Borne Disease. New York: American Elsevier.
- Proceedings of the New Jersey Mosquito Control Association, Annual Meetings.
- Worth, C.B. 1972. Of Mosquitoes, Moths, and Mice. New York: Norton and Co.