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Fish Pond Mosquito (Culiseta incidens)

May contain: invertebrate, insect, animal, and mosquito
Fish Pond Mosquito (Culiseta incidens). Photographer: Sean McCann

Fish Pond Mosquitoes (Culiseta incidens) are one of 53 types of mosquitoes that occur in California and are found in all California counties.

This mosquito is usually found breeding in fishponds, creeks, and containers and is the second leading cause of service requests for the District. Small sources, such as buckets, cans and tires, can produce sufficient numbers to cause discomfort in a neighborhood. This mosquito is moderately aggressive and bites in the evening or in shady places during the day. It is easily noticed because of its large size and dark spotted wings.

This species primarily occurs west of the Rocky Mountains, from Alaska to the Southern California border. Breeding records have been reported from Texas, Michigan, Nebraska, North Dakota, and several provinces in Canada. In California it occurs from below sea level to at least 9,500 feet elevation, which is indicative of its adaptiveness and distribution on the West Coast.

Diseases Transmitted

Fish Pond Mosquitoes are primarily a domestic nuisance and in some regions are considered relatively unimportant as a human pest. Although not found to be naturally infected with mosquito-borne diseases, successful laboratory experimental transmission of St. Louis Encephalitis, Western Equine Encephalitis and Japanese B Encephalitis virus does indicate a potential medical importance for this mosquito.

Life Cycle

Adult Daily Activity

This species is most abundant in the spring and fall during periods of cool, moderate temperatures. Although influenced by many factors, the female life expectancy usually ranges from two to three weeks. In colder regions, the females overwinter by hibernating, but where temperatures are moderate, such as along the California coast, development continues throughout the year.

Humans frequently encounter this species while sitting around swimming pools, camping, working in the yard or engaging in outdoor activities such as backyard barbecues. Adults will enter dwellings but not as frequently as some other types of mosquitoes.

Where large populations exist, male swarming flights may be observed around twilight. Mating often takes place in conjunction with the male swarms. Most breeding sites are located near the area of complaints

Adult Flight Range

This mosquito tends to stay near its breeding site but is capable of traveling up to five miles.

Adult Feeding

Females feed primarily on birds and domestic animals but are troublesome pests in areas where they feed on humans. Bites are experienced mostly in shady areas during the twilight hours, when the mosquito is most active. Males do not bite, but feed on nectar and plant juices. Females may also feed on plant juices, but usually must have a blood meal in order to develop their eggs. Remaining indoors or away from breeding areas will often serve to protect individuals from its bite.

Eggs and Larvae

An adult female lays about 150-200 eggs in clusters called rafts which float on the surface of the water until they hatch in about two days. Larvae are found in a wide variety of standing water sources including creeks, fish ponds, abandoned swimming pools, stagnant and polluted waters, log ponds, reservoirs, snow pools, brackish water, horse troughs, artificial containers, and even discarded automobile tires. The large and normally dark larvae and pupae can readily be observed moving about in the water.