Washington State hosts 19 distinct mosquito species that emerge throughout different seasons, each with unique habitats and behaviors that directly impact your outdoor activities.
While some species like the Northern house mosquito are merely nuisances, others such as the Western encephalitis mosquito can transmit serious diseases.
Understanding these differences helps you protect your family and enjoy Washington’s beautiful outdoors more safely.
This identification guide covers every mosquito species you’ll encounter across Washington’s diverse ecosystems, from urban backyards to mountain wetlands.
You’ll learn to recognize each species by their distinctive markings, understand their seasonal patterns, and discover which ones pose the greatest health risks in your specific region.
Western Encephalitis Mosquito
The Western encephalitis mosquito (Culex tarsalis) ranks as Washington’s most medically significant mosquito species due to its ability to transmit West Nile virus and Western equine encephalitis. You’ll recognize this medium-sized mosquito by its golden-brown coloration and distinctive white bands on its legs and proboscis.
This species thrives in irrigated agricultural areas, particularly around dairy farms, rice fields, and other water-holding agricultural sites. Peak activity occurs during warm summer evenings when temperatures remain above 60°F. The Western encephalitis mosquito prefers to feed on birds but will readily bite humans when bird hosts are scarce.
Important Note: This species is the primary vector for West Nile virus in Washington State. Cases typically peak in late summer when mosquito populations reach their highest densities.
Female Western encephalitis mosquitoes lay their eggs in rafts on the surface of permanent or semi-permanent water sources. Development from egg to adult takes approximately 14-21 days under optimal conditions. You’ll find this species most active in blood-feeding insects communities throughout eastern Washington’s agricultural regions.
Northern House Mosquito
The Northern house mosquito (Culex pipiens) represents the most common urban mosquito species across Washington State. This brown-colored mosquito with unremarkable markings breeds prolifically in artificial containers, storm drains, and neglected swimming pools around residential areas.
You’ll encounter this persistent species from late spring through early fall, with populations peaking during warm, humid summer months. Northern house mosquitoes exhibit strong preference for human blood and will enter homes through open doors and windows to feed on sleeping residents.
| Characteristic | Northern House Mosquito | Comparison Species |
|---|---|---|
| Size | 4-6mm | Similar to most Culex species |
| Color | Brown with pale bands | Less distinctive than Aedes species |
| Breeding Sites | Artificial containers | More urban-adapted than rural species |
| Disease Risk | Low to moderate | Lower than Western encephalitis mosquito |
This adaptable species overwinters as mated females in protected locations like basements, garages, and crawl spaces. Understanding Culex mosquito biology helps explain why Northern house mosquitoes remain active longer than other species in urban environments.
White-Dotted Mosquito
The White-dotted mosquito (Culex restuans) closely resembles the Northern house mosquito but displays distinctive white spots on its abdomen. This early-season species emerges in spring when temperatures consistently reach 50°F and typically disappears by midsummer as other species take over.
You’ll find White-dotted mosquitoes breeding in temporary pools, tree holes, and containers with organic-rich water. Unlike their house mosquito relatives, this species shows stronger preference for bird blood but will feed on humans when necessary. Their early emergence makes them important in disease transmission cycles involving migratory species returning to Washington.
Pro Tip: White-dotted mosquitoes serve as early indicators of mosquito season. Their appearance in April signals the start of mosquito activity across Washington State.
Snow Pool Mosquito
The Snow pool mosquito (Aedes communis) emerges from snowmelt pools in mountainous regions throughout Washington’s Cascade and Olympic ranges. This hardy species displays dark coloration with silver-white scaling on its thorax and distinctive banded legs.
You’ll encounter aggressive swarms of Snow pool mosquitoes during late spring and early summer hiking trips above 2,000 feet elevation. These mosquitoes breed exclusively in temporary pools formed by melting snow, completing their entire development cycle within 4-6 weeks before pools dry up.
Female Snow pool mosquitoes lay drought-resistant eggs in depression areas that will hold snowmelt the following year. This adaptation allows the species to thrive in harsh mountain environments where other mosquitoes cannot survive. Hikers exploring high-elevation wildlife habitats should prepare for intense mosquito activity during peak emergence periods.
Floodwater Mosquito
The Floodwater mosquito (Aedes vexans) ranks among Washington’s most aggressive biters, emerging in massive numbers following spring floods and heavy rainfall events. This medium-sized mosquito features brown coloration with golden scaling and will travel several miles from breeding sites to find blood meals.
Floodwater mosquitoes breed in temporary pools created by flooding rivers, irrigation overflow, and seasonal wetlands. Their eggs can survive dry conditions for months, hatching rapidly when flooded. Peak emergence typically occurs 7-10 days after major flooding events throughout Washington’s river valleys.
- Eggs survive drought conditions in flood-prone areas
- Heavy rains or floods trigger synchronized hatching
- Larvae develop rapidly in nutrient-rich floodwater
- Adults emerge in massive swarms seeking blood meals
- Mated females disperse to lay eggs in suitable sites
This species demonstrates remarkable dispersal ability, with marked individuals recovered up to 20 miles from breeding sites. Understanding Washington mosquito surveillance patterns helps predict when and where Floodwater mosquito outbreaks will occur.
Banded Spring Mosquito
The Banded spring mosquito (Aedes cinereus) appears during cool spring months when other mosquito species remain dormant. You’ll identify this species by its distinctive white bands on dark legs and its preference for shaded woodland areas near streams and seeps.
This cold-tolerant species begins activity when temperatures reach just 45°F, making it one of the earliest mosquitoes you’ll encounter during Washington’s spring season. Banded spring mosquitoes breed in small, temporary pools in forested areas, particularly those fed by groundwater seepage.
Key Insight: Banded spring mosquitoes serve as important pollinators for early-blooming woodland flowers, making them ecologically beneficial despite their biting behavior.
Summer Mosquito
The Summer mosquito (Culiseta inornata) represents Washington’s largest mosquito species, with females reaching up to 8mm in length. Despite their intimidating size, Summer mosquitoes are relatively weak fliers and prefer to feed on large mammals rather than humans when given the choice.
This species breeds in permanent water bodies including ponds, marshes, and slow-moving streams throughout Washington’s lowland areas. Summer mosquitoes exhibit peak activity during warm summer evenings, particularly in areas with abundant cattle or other livestock.
| Feature | Summer Mosquito | Average Mosquito |
|---|---|---|
| Size | 6-8mm | 3-6mm |
| Flight Strength | Weak, short distances | Moderate to strong |
| Host Preference | Large mammals | Varies by species |
| Breeding Habitat | Permanent water | Various water types |
Winter Mosquito
The Winter mosquito (Culiseta incidens) demonstrates remarkable cold tolerance, remaining active well into Washington’s winter months when temperatures allow. This large, dark-colored mosquito breeds in tree holes, artificial containers, and protected water sources that don’t freeze completely.
You might encounter Winter mosquitoes during mild winter days, particularly in western Washington’s temperate coastal regions. Their ability to remain active at low temperatures makes them unique among Washington’s mosquito fauna and important for understanding climate adaptation in insects.
Common Mistake: Many people assume all mosquitoes die in winter, but Winter mosquitoes can remain active year-round in mild coastal climates.
Spring Snow Mosquito
The Spring snow mosquito (Aedes cataphylla) emerges from high-elevation snowmelt pools throughout Washington’s mountain ranges. This cold-adapted species displays robust build and dark coloration that helps absorb solar radiation in cool mountain environments.
Spring snow mosquitoes complete their development in temporary pools created by melting snow, typically at elevations above 3,000 feet. Their larvae can tolerate near-freezing water temperatures and develop successfully even when pools partially refreeze at night.
Female Spring snow mosquitoes exhibit extreme host-seeking behavior, flying considerable distances to locate blood meals necessary for egg development. Mountain recreationists often encounter dense swarms of these mosquitoes during late spring backcountry trips in areas with diverse alpine wildlife.
Common Malaria Mosquito
The Common malaria mosquito (Anopheles freeborni) represents Washington’s only Anopheles species capable of transmitting malaria parasites. While malaria transmission doesn’t currently occur in Washington, this species remains medically significant due to its potential role in disease outbreaks.
You’ll identify Common malaria mosquitoes by their distinctive resting position with abdomen angled upward, unlike other mosquito species that rest parallel to surfaces. They prefer clean, permanent water sources including ponds, slow streams, and irrigation channels for breeding.
- Adults rest with characteristic upward-angled abdomen
- Larvae lack respiratory siphon, breathing through spiracles
- Prefer clean, sunlit water for breeding
- Most active during evening and nighttime hours
- Feed primarily on mammals including humans
Historical records indicate malaria transmission occurred in Washington during the early 1900s, making continued surveillance of this species important for public health preparedness. Understanding vector-borne disease risks helps explain why monitoring continues despite current absence of local transmission.
Western Treehole Mosquito
The Western treehole mosquito (Aedes sierrensis) breeds exclusively in water-filled tree holes, particularly in oak woodlands throughout southwestern Washington. This specialized species has adapted to the unique chemistry and limited space of tree hole environments.
Western treehole mosquitoes demonstrate strong site fidelity, with females returning to the same tree holes generation after generation. Their larvae feed on organic matter that accumulates in tree holes, including fallen leaves, dead insects, and other detritus.
This species plays an important ecological role in tree hole ecosystems, helping decompose organic matter while serving as food for other tree hole inhabitants. Their specialized habitat requirements make them vulnerable to forest management practices that remove older trees with suitable cavities.
Woodland Mosquito
The Woodland mosquito (Aedes increpitus) inhabits forested areas throughout Washington’s temperate rainforests and mixed woodlands. This shade-loving species breeds in small, temporary pools within forest understories, particularly those created by seasonal flooding or heavy rainfall.
Woodland mosquitoes exhibit crepuscular activity patterns, becoming most active during dawn and dusk when light levels are low. Their dark coloration provides excellent camouflage against tree bark and forest debris, making them difficult to spot until they begin feeding.
Pro Tip: Woodland mosquitoes are most problematic during spring when temporary pools are abundant but natural predators haven’t yet established populations.
Female Woodland mosquitoes require multiple blood meals for egg development, making them persistent biters in suitable forest habitats. Their preference for shaded environments means they remain active during midday hours when most mosquitoes seek shelter, affecting hikers and forest workers exploring Washington’s forest ecosystems.
Saltmarsh Mosquito
The Saltmarsh mosquito (Aedes dorsalis) thrives in Washington’s coastal salt marshes and estuarine environments along Puget Sound and the Pacific coast. This salt-tolerant species breeds in tidal pools and brackish water areas that experience regular saltwater intrusion.
Saltmarsh mosquitoes synchronize their breeding cycles with tidal patterns, laying eggs in areas that will be flooded by spring tides. Their larvae can survive in water with salinity levels approaching that of seawater, giving them exclusive access to breeding sites unavailable to freshwater species.
You’ll encounter Saltmarsh mosquitoes primarily in coastal areas during summer months when warm temperatures and optimal salinity levels support rapid development. Their strong flight capabilities allow them to disperse several miles inland from breeding sites, affecting coastal communities and recreational areas.
Sapphire Mosquito
The Sapphire mosquito (Uranotaenia sapphirina) represents one of Washington’s most distinctive mosquito species with its metallic blue-green coloration and small size. This beautiful species breeds in permanent water bodies with abundant aquatic vegetation, particularly those with neutral to slightly alkaline pH.
Sapphire mosquitoes exhibit unusual feeding behavior, with adults feeding primarily on amphibian blood rather than mammalian hosts. This specialization makes them less troublesome to humans but ecologically important in wetland food webs where they interact with Washington’s native amphibians.
| Characteristic | Sapphire Mosquito | Typical Mosquito |
|---|---|---|
| Coloration | Metallic blue-green | Brown to black |
| Size | 2-3mm (very small) | 4-6mm |
| Host Preference | Amphibians | Mammals/birds |
| Habitat | Vegetated permanent water | Various water types |
Swamp Mosquito
The Swamp mosquito (Aedes excrucians) inhabits Washington’s freshwater swamps, marshes, and seasonal wetlands throughout both eastern and western regions. This medium-sized mosquito displays distinctive white-scaled markings on its dark thorax and legs.
Swamp mosquitoes emerge in multiple broods throughout the growing season, with populations peaking during warm, humid periods following rainfall. Their larvae develop in shallow, temporary pools within swamp environments, particularly those rich in organic matter and partially shaded by vegetation.
This species demonstrates strong dispersal behavior, with adults traveling up to 10 miles from breeding sites to locate suitable hosts. Swamp mosquitoes prefer feeding on large mammals but will readily bite humans, making them significant pests in recreational areas near wetlands.
Striped Mosquito
The Striped mosquito (Aedes pullatus) displays prominent white stripes on its legs and thorax, making it one of Washington’s most easily recognizable mosquito species. This container-breeding species has adapted well to urban and suburban environments throughout the state.
You’ll find Striped mosquitoes breeding in artificial containers including flower pots, bird baths, and clogged gutters around residential areas. Their eggs can survive dry conditions for several months, allowing populations to persist through Washington’s dry summer periods.
Important Note: Striped mosquitoes are aggressive day-biters, making them particularly troublesome during outdoor activities when most mosquitoes are inactive.
Female Striped mosquitoes exhibit multiple feeding behavior, taking several small blood meals rather than one large feeding. This behavior increases disease transmission potential and makes them persistent pests around homes and businesses where indoor-outdoor insects create ongoing problems.
Ochlerotatus Fitchii Mosquito
The Ochlerotatus fitchii mosquito (Aedes fitchii) inhabits woodland areas throughout Washington’s forested regions, breeding in temporary pools created by spring snowmelt and seasonal rainfall. This shade-tolerant species displays mottled brown coloration that provides excellent camouflage in forest environments.
Ochlerotatus fitchii mosquitoes emerge during cool spring months when forest canopies are still developing, taking advantage of increased sunlight reaching temporary pools. Their development synchronizes with amphibian breeding seasons, creating complex ecological interactions in forest wetlands.
This species exhibits strong host-seeking behavior during cool weather when other mosquitoes remain inactive. Forest workers and early-season hikers often encounter aggressive swarms of Ochlerotatus fitchii mosquitoes in areas with suitable breeding habitat and abundant wildlife hosts.
Northern Mosquito
The Northern mosquito (Aedes punctor) represents Washington’s most cold-tolerant species, remaining active at temperatures as low as 40°F. This hardy mosquito breeds in permanent and semi-permanent water bodies throughout northern Washington and high-elevation areas.
Northern mosquitoes display remarkable longevity, with adults surviving several months under favorable conditions.
Their extended lifespan allows them to bridge seasonal gaps when other species are absent, maintaining continuous mosquito activity in suitable habitats.
You’ll encounter Northern mosquitoes primarily in cooler regions of Washington, including mountain valleys, northern forests, and areas influenced by marine climates.
Their cold tolerance makes them important components of Pacific Northwest ecosystem dynamics throughout extended growing seasons.
Understanding these 19 mosquito species helps you prepare for outdoor activities across Washington’s diverse environments.
Each species presents unique challenges and opportunities for control, from eliminating breeding sites around your home to using appropriate protection during wilderness adventures.
By recognizing the seasonal patterns and habitat preferences of different mosquito species, you can better protect yourself and your family while enjoying everything Washington State has to offer.
Remember that mosquito activity varies significantly based on weather patterns, local habitat conditions, and seasonal timing.
Staying informed about current mosquito surveillance data and implementing integrated pest management strategies around your property will help minimize encounters with these persistent insects while supporting the ecological balance they maintain in Washington’s complex insect communities.
