Where Do Mosquitoes Lay Eggs?

Eggs hatch within 24–48 hours and must hatch quickly because they have essentially no desiccation resistance. Culex pipiens is NH's primary West Nile Virus vector. Aedes / Ochlerotatus (Ae. vexans, Ae. canadensis, Ae. triseriatus, Ae. japonicus, Ae. excrucians, Ae. stimulans): Females lay individual eggs glued above the waterline on damp substrates — container walls, moist soil in flood-prone meadows, salt marsh edges. These eggs are highly desiccation-resistant and hatch only when water rises to meet them. Aedes vexans eggs survive dry for up to three years in NH soil (Walter Reed Biosystematics Unit). Culiseta (Cs. melanura, Cs. morsitans): Lay rafts similar to Culex, but in highly specific habitat — acidic swamp water and subterranean root crypts of red maple and Atlantic white cedar swamps. Cs. melanura uniquely overwinters as larvae in these crypts (Andreadis et al. 2012), then matures in spring. It is the EEE enzootic vector but rarely bites humans directly. Coquillettidia (Cq. perturbans): Lays rafts of 150–350 eggs on permanent freshwater marsh surfaces near emergent vegetation. After hatching, larvae and pupae attach to cattail and sedge roots underwater, piercing the aerenchyma tissue with a modified siphon to draw oxygen directly from the plant — never surfacing where most larvicides act (UF IFAS EENY-694). Anopheles (An. punctipennis, An. quadrimaculatus, An. walkeri): Lay individual eggs on water surfaces with lateral floats that keep them stable. Found in permanent ponds and marshes. Historic malaria vectors; currently a JCV bridge vector in NH.

Culex pipiens eggs are not desiccation-resistant — they must hatch within days of being laid, which is why weekly emptying of bird baths, gutters, and containers works decisively against Culex and significantly reduces WNV risk in your immediate area. By contrast, Aedes eggs are built for survival. The CDC states Aedes eggs 'stick to container walls like glue' and 'can survive drying out for up to 8 months.' Laboratory studies on Ae. aegypti measured 88% egg viability at 56 days and 2–15% viability after a full year (Faull & Williams 2015, J Vector Ecol, PubMed 26611964). For NH's most consequential nuisance species, Aedes vexans, the Walter Reed Biosystematics Unit documents that eggs 'can survive desiccation and weather extremes for up to three years.' These eggs wait in NH soil — dry meadows, roadside ditches, lawn low spots — and hatch explosively within hours of flooding by rain, snowmelt, or seepage. A dry summer field that has never held visible standing water can produce an explosive biting brood of Ae. vexans days after a heavy thunderstorm.

After hatching from egg rafts on marsh surfaces, Cq. perturbans larvae swim down and attach to cattail and sedge roots with a modified sclerotized siphon that pierces the plant's aerenchyma tissue, drawing oxygen directly from the plant rather than the water surface (UF IFAS EENY-694). The larvae spend their entire development period — and the pupal stage — underwater, attached to roots. They never come to the surface where Bti and other larvicides act. A Rutgers trial found that doubling the standard Bti application rate on Cq. perturbans habitat achieved only about 60% larval reduction — far less effective than typical surface-breeder control. This biology explains why communities near cattail marshes in southeastern NH experience intense biting at dusk in late June and July despite aggressive source reduction efforts.

Unlike the other genera discussed here, Cs. melanura breeds in highly cryptic habitat: the acidic, tannin-stained water in root cavities and subterranean pools beneath red maple swamps and Atlantic white cedar swamps. These are the same wetland types that dominate the high-risk EEE corridor from Hampstead and Danville through Kensington and Kingston. Cs. melanura overwinters uniquely as larvae in these root crypts — protected from winter cold by the soil — and resumes development in spring. It feeds almost exclusively on birds and rarely bites humans directly; human EEE cases occur when bridge vectors (Cq. perturbans, Ae. canadensis, Ae. vexans) acquire the virus from birds and then bite people. No homeowner can meaningfully treat Cs. melanura habitat — it requires municipal-scale larviciding of wetland margins.

Aedes excrucians and Ae. stimulans emerge from snowmelt woodland pools in April–May and are early carriers of Jamestown Canyon Virus (JCV). Aedes vexans and Cq. perturbans reach nuisance and egg-laying peak in July after summer flooding events. Culex pipiens WNV oviposition peaks in August when temperatures are highest and the bird–mosquito transmission cycle has amplified the virus. Culiseta melanura EEE amplification in bird populations peaks in late August and September — historically when human EEE cases are diagnosed in NH. After the first hard frost, adult mosquitoes die, Culex pipiens females enter winter diapause in basements and culverts, Cs. melanura larvae overwinter in swamp root crypts, and Aedes eggs enter dormancy in soil to wait for next spring's flooding.