E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Aedes sierrensis (Ludlow)
Mosquito
Family: Culicidae
Species account author: Peter Belton.
Extracted from The Mosquitoes of British Columbia (1983)

© Sean McCann  Email the photographer   (Photo ID #8927)

E-Fauna BC Static Map
Distribution of Aedes sierrensis in British Columbia
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Species Information


Click on the image(s) below to view an expanded illustration for this taxon.



Illustration 2


A small to medium-sized mosquito, breeding in tree-holes, its tarsal segments with characteristic silvery white bands; wing length 2.9-4.8 mm.

Female

Proboscis dark-scaled. Palps dark, apices of segments white-scaled, distal segment entirely white in some specimens. Pedicels dark, dorsomedian surface white-scaled. Scutum with a median stripe and curved lateral lines of golden scales on a background of curved dark brown scales. No lower mesepimeral setae or postprocoxal or hypostigmal scale patches. Abdominal tergites dark with strongly contrasting white basal bands, widest at centre, narrowing laterally. Hind tarsomeres 1 & 4 with broad silvery white basal and apical bands, 2 & 3 with broad basal and narrow apical bands, 5 entirely white. Wings dark, a patch of white scales at base of C.

Larva

Antennae smooth, 1-A unbranched (as in hendersoni). Head setae 5 & 6-C 1 or 2-branched. 12-23 long comb scales in a patch. Siphon about 3 x 1, pecten evenly spaced on basal ¼ to 1/3. 1-S many branched, inserted before mid siphon. Saddle small, reaching about half way around anal segment. 1-X long, 2-branched. Papillae long broad and bluntly rounded, and swimming setae sparse (as in hendersoni).



Glossary of Terms [PDF]

Genus Description


Aëdes is the Greek word for disagreeable. Without the dieresis the word means house or building. Although Meigen did not use a dieresis, he translated it as troublesome. Some authorities, therefore, write the generic name Aëdes. Most species of British Columbian mosquitoes belong to this genus. The females all have short palps, usually less than one quarter of the length of the proboscis, and in both sexes the posterior margin of the scutellum is tri-lobed with the setae in three tufts.

Aedes is a large and variable genus and in the field the most reliable character to separate females from other mosquito genera is the pointed abdomen. Males can be identified in the field by their large and separated gonocoxites but if these are not obvious the thorax can be examined for the presence of postspiracular setae which are absent in the males of Culex, Culiseta, and Mansonia. A slide of the terminalia, as well as confirming the genus, can be used to determine the species. (See Wood et at. 1979).

When at the water surface, the larvae of all culicines hang downwards from the hydrophobic tip of the siphon and are thus easily distinguished from anophelines.

Aedes larvae can be distinguished from those of Culex and Culiseta by the position of the siphon seta (1-S). It is never at the base of the siphon in aedines and can be seen with a hand lens if the larva cooperates.

The pupae are hard to identify. It is usually simpler to let them emerge.

Nearly all aedine adults in British Columbia die in late summer or autumn. The eggs are laid singly or in clusters, usually in crevices at the margins of suitable breeding sites. They do not float. Most aedines overwinter as eggs.

Biology

Species Information

This species was known as varipalpus until 1957 (Belkin & MacDonald). Like hendersoni, it breeds in tree-holes but sierrensis is also occasionally found in artificial containers. Eggs laid in late summer are reported to hatch in the fall and winter is spent in the larval stage. I have found that eggs laid in captivity in the Lower Mainland will hatch when immersed in early December and evidently do not have a rigid diapause. Fourth instar larvae, however, will not pupate until the days reach a critical length in the following spring (Arnell & Nielsen 1972). Sierrensis breeds in holes in a variety of deciduous trees across the south of the Province and, in the Kootenays, was once discovered 500 m above the treeline in an artificial container (Dyar 1904). The most northerly record is from Terrace (Arnell & Nielsen 1972). Males have the habit of dodging around warm-blooded animals, where they seize and mate with females that approach to take blood. Biting females enter houses in the Lower Mainland between May and August. Adults vary greatly in size. They tend to be small when temperatures are high, but their size is probably also influenced by the nutrient content of the water in the breeding site. The smallest females can penetrate normal insect screening (7/cm mesh).

Control of larvae in the breeding sites is usually impractical, although rot cavities in garden and boulevard trees should be plugged when found. Fine window screening is probably the best solution in wooded areas. The release of sterile males or biological control techniques using parasites or predators would be worth investigating if the species becomes an important pest. It transmits Dog heartworm (Dirofilaria immitis) in many parts of its range.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS5No StatusNot Listed
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Notes

"This species can be a significant pest on the west coast and the south of the Province, biting during the day and entering houses. It develops in tree cavities and shaded artificial containers, overwintering in the larval stage or as eggs if the late summer is dry. Its West Nile Virus (WNv) infection and transmission rates were low in California tests (Goddard et al. 2002). It has not been found with WNv in the wild and, because it seems not to bite birds, may not be an important virus vector". (Belton 2007, with permission).

References

Belton, Peter. 2007. British Columbia mosquitoes as vectors of West Nile virus. Peter Belton web site. Simon Fraser University.

Synonyms and Alternate Names

Ochlerotatus sierrensis (Ludlow)

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 12/11/2019 9:07:15 AM]
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