Distinguishing Aedes albopictus, the Asian Tiger mosquito, from native British mosquitoes
Source: gov.uk (2025-03-06)

False reports of possible Asian Tiger mosquitoes (Aedes albopictus) have been received by MEZE. This page outlines differences between this species and similar native species.

CCHS navigation menu: CCHS homepage (https://www.gov.uk/government/organisations/the-centre-for-climate-health-security)Topic: health impacts (https://www.gov.uk/government/collections/health-impacts) Vector-borne disease: mosquitoes (https://www.gov.uk/government/collections/mosquitoes)Part of: learning about mosquitoes

Culiseta annulata

Culiseta annulata is one of the most common mosquito species in the British Isles. It thrives in a diverse range of natural and artificial water bodies, such as ponds, ditches, marshes, garden water butts, and cisterns. These breeding sites can be sunlit or shaded, fresh or brackish, clean or polluted.

Unlike most British mosquitoes, Culiseta annulata remains active throughout the year in all life stages—eggs, larvae, pupae, males, and females—without entering diapause. Diapause a dormant state triggered by unfavourable environmental conditions. This unique trait allows them to overwinter successfully, making them one of the few mosquito species active in late autumn and early spring. Reports of mosquito bites during these seasons are almost always linked to this species.

Adult females feed both indoors and outdoors on a variety of vertebrate hosts, including humans and birds, contributing to their widespread presence and persistence.

Key features:
- large compared to other British mosquitoes (13 to 15 mm)
- brown in colour and lack a white stripe on their thorax
- collections of black scales on their wings which make them appear spotted
- distinctly striped legs
Aedes geniculatus

Aedes geniculatus mosquitoes are mostly found in forests with a mix of trees or mainly deciduous trees. It is rare in forests with only conifers. They are found in urban areas where there are old trees (for example horse chestnut, beech or London plane). These mosquitoes can cause nuisance biting.

They lay their eggs in tree holes and stumps especially in water-filled beech tree holes, but they can also use objects like old tyres. The water they breed in usually has a lot of organic matter and tannins.

Their eggs can survive cold weather and drying out. In colder places, they spend winter as eggs, while in warmer places, they survive as larvae. They feed on different animals, including humans, cows, birds, and reptiles. Female mosquitoes bite during the day and at twilight.

Adult emergence begins in May and there are 2 generations per year with the last adults occurring in September.

Notable features include:
- white spots on its ‘knees’
- the back (scutum) has two black stripes in the middle - these stripes may be joined together or completely separated by a pale stripe
- the lower leg segments (tibiae and tarsi) are covered in black scales
Culex pipiens s.l./ Culex torrentium

Culex pipiens sensu lato and Culex torrentium are 2 mosquito species in Britain that look almost the same, except for differences in male genitalia. Cx. pipiens has two types: pipiens and molestus. The pipiens type is the most common mosquito in Britain, found across England, Scotland, and Wales. The molestus type lives mostly in underground shelters and is less often recorded.

Both species hibernate in winter. Male Cx. pipiens die, while females find places to survive until spring. Adults appear in May, peak in June, and females switch to feeding on plant juices after August to prepare for winter.

They breed in many water sources, including ponds, ditches, marshes, water tanks, and buckets. The pipiens type is common in temporary water like puddles and flooded grasslands. Cx. torrentium also lays eggs in tree holes and containers.

Notable features include:
- light to medium-sized and mostly brown - it may have some pale scales on its body
- its abdomen being rounded, with pale bands at the base of each segment
- legs that are plain and do not have the light and dark rings found on some other mosquitoes
Reasons for confusion over identification

The most likely reasons why many people confuse these 2 mosquito species for the Asian Tiger mosquito are:
- Cs. annulata is large and has very distinctive and boldly striped legs similar to Ae. albopictus
- Ae. geniculatus has very white scales on a black body similar to Ae. albopictus
There are 3 important differences between Cs. annulata and Ae. albopictus:
- Although both species have legs that have rings of white scales which give a banded appearance, Cs. annulata is much larger than Ae. albopictus with a wing span 13 to 15 mm, compared to 7 to 8 mm,
- Cs. annulata also have clusters of scales on their wings which make them look spotted; this does not occur on the wings of Ae. albopictus,
- The thorax of Ae. albopictus has a single white central line from front to back; this does not occur on Cs. Annulata.
There are 2 important differences between Ae. geniculatus and Ae. albopictus:
- the bright white scales on a black body of Ae. albopictus can also be confused with similar bright white scales on Ae. geniculatus; however, the latter differs in that tarsi on the legs are not banded, except for a white tip to the femurs (appearing as white ‘knees’)
- the thorax on Ae. geniculatus has many white lines, and not just a central line as in Ae. albopictus
This table show the main differences between Ae. albopictus and commonly found British species.