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Los Angeles County West Vector & Vector-Borne Disease Control District
Mosquito Ecology
What is a Mosquito?
Any winged insect of the family Culicidae, order Diptera, having a narrow abdomen, a
long and slender proboscis, and narrow wing scales on the wing margins and veins.
Males have feather-like antennae and mouthparts which are not adapted for piercing.
Females have slender antennae and a set of needlelike organs in the proboscis with which
they puncture the skin of animals to feed on their blood.
In some species (Aedes spp.), eggs are laid directly on or into soils that will later be flooded. Other species lay their eggs directly on the water either singularly (Anopholes spp.) or in egg rafts(Culex spp.). The larvae, sometimes called wigglers because of their swimming motions, are aquatic, but usually come to the surface to breathe. The pupae, sometimes called tumblers because of their swimming motions, are also aquatic and generally found at the water surface. Many species pass through several generations a year and hibernate through the winter as adults; others overwinter in the egg or mature larval stage. Some mosquitoes are important in the transmission of disease-causing agents, whereas others are important more for their pestiferous habits.
Mosquitoes must have water to complete
their life cycle.
Only seven days are required to
complete their life cycle (egg to adult) during warm weather.
Mosquitoes do not develop in grass or
shrubbery, although flying adults frequently rest in these areas during daylight hours.
Only the female mosquito bites to
obtain a blood meal. The male mosquito lives only on plant juices.
The female may live as long as three
weeks during the summer or many months over the winter in order to lay her eggs in the
following spring.
The Mosquito Life Cycle
- EGG RAFT
The most common mosquitoes lay egg rafts that float on the water. Each raft
contains from 100 to 400 eggs. Some mosquitoes lay their eggs singularly on the
water surface, and some lay their eggs on rocks and vegetation awaiting to be submerged by
a strong rain. Within a few days of being laid or submerged by water, the eggs hatch
into larvae.
- LARVA
The larva or "wiggler" comes to the surface to breathe through a tube called a
siphon. It molts (sheds its skin) four times during the next several days.
These molts are called instars. It grows rapidly between each molt. After the
fourth instar it changes into a pupa.
-
PUPA
The pupa or "tumbler" cannot eat. It breathes through two tubes on its back called a siphon. The adult mosquito grows inside the pupa and in two days or so, when it is fully developed, it splits the pupal skin and emerges as an adult mosquito.
ADULT
The newly emerged adult rests on the surface of the water until it is strong enough to
fly away and feed.
Common Mosquitoes Found
in Los Angeles County
Culex tarsalis (CT), the principal vector for
WNV, SLE and WEE in California.
Culex quinquefasciatus (CQ) is commonly called the
southern house mosquito. Culex quinquefasciatus is not a primary vector
of WNV, SLE, or WEE. CQ primarily bite birds and do not use humans as a
preferred blood source. Culex quinquefasciatus are much less
efficient than
Culex tarsalis in transmitting WNV, SLE, & WEE to humans.
Culiseta incidens (CI) is commonly called the
cool-weather mosquito. Culiseta incidens is not known to transmit
any diseases to humans. They are considered only pestiferous in nature. However,
they are believed to be a transmitter of dog heartworm.
Culex erythrothorax (CE) has been found naturally infected with WNV, SLE, and WEE viruses, but is generally not considered a significant vector of these diseases.
Culex stigmatosoma (CS) may act as enzootic amplifiers of SLE viruses in nature.
