About Mosquitoes
Mosquitoes are small flying insects found throughout the United States and are known for feeding on the blood of humans and animals. Only female mosquitoes bite, using blood to support egg development. Mosquitoes are active in a wide range of habitats and are associated with standing water, warm temperatures, and humid environments.
Physical Characteristics of Mosquitoes
Adult mosquitoes typically measure between 1/8” and 1/4” in length. They have slender bodies, long legs, and one pair of narrow wings covered in fine scales.
Mosquitoes are identified by:
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A long, thin proboscis used for piercing skin
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Antennae that vary between males (feathery) and females (threadlike)
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Distinct wing patterns depending on species
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A lightweight body adapted for hovering flight
Larvae and pupae are aquatic and develop in still or slow-moving water.
Mosquito Appearance in California
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The Southern house mosquito is common in urban and suburban regions and appears light brown with narrow wings.
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The Western encephalitis mosquito is typically darker and associated with agricultural and rural settings.
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Aedes mosquitoes, including Aedes aegypti and Aedes albopictus, which have expanded across California in recent years, are identifiable by their black bodies with white striping.
These species differ in their activity schedules, preferred breeding sites, and regional distribution.
Breeding Requirements and Lifecycle
Mosquitoes require standing water to complete their development. Females lay eggs on or near water sources such as:
- Containers
- Birdbaths
- Gutters
- Irrigation runoff
- Flooded soil
- Ponds or slow-moving streams
- Wet vegetation
The lifecycle consists of four stages: egg, larva, pupa, and adult. Development time varies with temperature and can be as short as seven to ten days in warm conditions.
Lifecycle Patterns in California
- Mild winters in many parts of California allow some mosquito species to remain active nearly year-round.
- Irrigation systems, especially in suburban and agricultural areas, create consistent breeding sites.
- Coastal and delta regions with marshes or wetlands support larger populations.
- Aedes mosquitoes, recently established, use small artificial containers for breeding, increasing activity in urban counties.
Climate variation creates significant differences in mosquito pressure across the state.
Feeding Behavior and Activity Times
Only female mosquitoes bite, using blood to produce eggs. Male mosquitoes do not bite and feed on nectar or plant juices. Mosquitoes detect hosts through body heat, carbon dioxide, and scent.
Feeding and activity traits include:
- Increased activity during dawn and dusk for many species
- Nectar feeding between blood meals
- Preference for shaded or sheltered areas during daylight
- Species-dependent host preference (birds, mammals, humans)
Different mosquito species feed at different times of day, which affects exposure risk.
Feeding Behavior Observed in California
- Aedes mosquitoes, now widespread in parts of California, are aggressive daytime feeders.
- Culex mosquitoes are most active at dusk and nighttime, contributing to evening biting pressure.
- Areas with irrigated vegetation or consistent moisture may have higher mosquito activity.
- Warm summer evenings increase mosquito movement throughout most regions of the state.
These patterns differ between coastal, inland, and desert climates.
Where Mosquitoes Are Commonly Found
Mosquitoes thrive in environments that provide both standing water and warm temperatures. Common locations include:
- Containers holding rainwater
- Clogged gutters
- Irrigated lawns
- Storm drains
- Birdbaths and fountains
- Marshy or wetland areas
- Shaded vegetation near moisture
They often rest in cool, humid areas during the day before becoming active again at dusk.
Common Mosquito Locations in California
- Coastal marshes and wetland preserves with stable humidity
- Central Valley irrigation systems, canals, and agricultural runoff
- Urban neighborhoods where Aedes mosquitoes use small containers and yard clutter
- Foothills and riparian corridors, which support Culex species
- Suburban areas with frequent watering, which maintain moisture throughout hot months
California’s diverse habitats support several mosquito species with varying behaviors and breeding cycles.
What Are the Risks of Mosquitoes?
Mosquitoes are considered significant public health pests due to their ability to transmit pathogens. While not every mosquito carries disease, certain species can spread viruses or parasites during feeding.
Potential concerns include:
- Itchy welts and skin irritation
- Allergic reactions in sensitive individuals
- Spread of viruses and other pathogens depending on species and region
- Increased outdoor discomfort during warm seasons
Different mosquito species pose different levels of risk depending on geography and climate.
Mosquito-Related Concerns in California
- West Nile virus is the most commonly reported mosquito-borne illness in the state, primarily transmitted by Culex mosquitoes.
- Expansion of Aedes aegypti and Aedes albopictus increases potential exposure to viruses found globally, though local transmission remains uncommon.
- Seasonal irrigation and warm temperatures encourage high summer activity.
- Marshes, wetlands, and coastal regions maintain mosquito presence beyond peak summer months.
These factors contribute to varying levels of mosquito activity across California throughout the year.