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Recognising mosquitoes

Not sure if that insect is a mosquito or something else? Below is some guidance on recognising mosquito adults and larvae and distinguishing them from other similar-looking insects.

A drawing of an adult mosquito
A drawing of a mosquito larva
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Recognising adult mosquitoes

You might recognise the sound of an adult mosquito better than the sight of one - a high-pitched whining in your ear late at night is likely to only be one thing. But how can you correctly identify the culprit?

The main identifying feature of an adult mosquito is its proboscis, the long tube extending from its mouthparts which it uses to suck blood and nectar. If you can't see a long proboscis, it probably isn't a mosquito! 

Proboscis

A drawing of a mosquito on a wall. It has a long proboscis (a tube pointing forwards from its head)

Clegs and biting midges: not-so-innocent victims of mistaken identity

Horseflies and deer flies, colloquially known as 'clegs', are common in many parts of Scotland and can be mistaken for mosquitoes due to their inclination to bite. However, they are a completely separate family of insects. Clegs are much bigger and stouter than mosquitoes and they do not have a proboscis. They have a much more painful bite than a mosquito bite - when a cleg bites you, you know about it! 

Biting midges are abundant in much of Scotland, particularly in the north-west. Again, they are a separate family to mosquitoes and in this case they are much smaller than mosquitoes. They do not have a proboscis. A midge bite is much less painful than a cleg bite but it can still be felt; typically as an itchy sensation. The Highland midge and many other biting midge species have dark grey patches on their wings, forming patterns that can be seen by eye. 

Size comparisons

Size comparison of different biting flies (horsefly, mosquito and biting midge). The horsefly is largest (approximately 19mm long). The mosquito is approximately 7mm long and the biting midge is approximately 2mm long.
  • Adult mosquitoes are small (usually 4-10mm in length), slender flies with long fragile legs.

  • They have scales on their wings which give the wings a hairy or dusty appearance. In some mosquito species, the wings are spotted.

  • Some species (but not all) have stripes on their legs.

Victims of mistaken identity

  • There are several other types of insects that are commonly mistaken for mosquitoes but are harmless! Below are some examples (non-biting midges, fungus gnats and crane flies). 

Crane fly
Fungus gnat
An image of a chironomid
  • You might be able to see that none of these insects has a long proboscis, although some of them have long antennae that could be mistaken for a proboscis. Remember that mosquitoes also have antennae, so mosquitoes have at least* three (two antennae + one proboscis) long extensions from their heads, while other insects just have two. If you can see at least three head extensions, it's almost certainly a mosquito. 

* Male mosquitoes and both sexes of some species have two additional long head extensions either side of the proboscis: the palps. You can find out more about the palps on our photo guidance page.

Tiger mosquitoes - more cases of mistaken identity

Aedes albopictus, known as the Tiger mosquito, is an invasive mosquito species in many parts of Europe. It is able to transmit several serious diseases. It is a small black and white mosquito with stripes on its legs. It is not found in Scotland.

There are at least 12 mosquito species native to Britain that have stripes on their legs and may consequently be mistaken for Tiger mosquitoes. In particular, the banded mosquito (Culiseta annulata) often causes alarm as it is very large and has black and white colouration. However, there are several key visible differences between the banded mosquito and the Tiger mosquito:

1. Size. The banded mosquito is almost double the size of the Tiger mosquito, with a wing span of up to 15mm compared with approximately 7mm in the Tiger mosquito.

2. Wings. The banded mosquito has spots on its wings, while the Tiger mosquito does not.

3. Legs. The tips of the banded mosquito's legs are black, while the Tiger mosquito has white tips at the end of its legs. 

So don't panic if you see a mosquito with striped legs in Scotland - the chances are it is a (relatively) harmless native species!

Banded mosquito

Native banded mosquito - NOT a Tiger mosquito!

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Mosquito larvae identification guidance

Unless you have a water barrel outside, you might never have seen or noticed mosquito larvae in Scotland. Read on to find out more about where you might see mosquito eggs and larvae and how to recognise them.

Mosquito eggs and larvae are found in standing water such as:

  • wetlands like bogs, marshes (including saltmarsh) and flooded grassland

  • reedbeds and ponds

  • puddles and footprints

  • artificial containers that have collected water, such as outdoor buckets, bird baths, gutters and plant pots

You will not find mosquito larvae in:

  • running water (e.g. flowing rivers and burns)

  • lochs (apart from at the edges if they are shaded and/ or have lots of vegetation)

  • the sea​​

Some mosquito species lay individual eggs on water surfaces or on substrates that are subject to flooding or waterlogging. Eggs are very small (approximately 0.8mm in length) and are only just visible to the naked eye. They are typically dark in colour and have a pointed oval shape. 

Other mosquito species lay eggs in 'rafts' - a collection of eggs stuck together on the water surface. Rafts can be up to 1cm in length and can be seen without a microscope. They are normally teardrop, semicircle or arc-shaped. If you have standing water in containers in your garden, you may see egg rafts at the surface during the spring and summer months.

A mosquito egg raft.
A mosquito egg raft.

Mosquito larvae go through four larval stages after hatching. The first stage is very small (approximately 1-2mm in length), but they can grow to over 1cm by the final stage. First stage larvae are usually pale and semi-translucent, but they often look darker and more opaque as they develop. 

 

The most distinctive feature of mosquito larvae is their behaviour. They rest just below the surface of the water to breathe, then wriggle quickly down to the bottom. Most Scottish mosquito species hang from the water surface with their head facing downwards, but a few species rest parallel below the surface. 

Videos: Rebecca Brown

Mosquito larva with siphon
Mosquito larva without siphon (Anopheles)

Most mosquito larvae have a siphon, which is a breathing tube at the base of the abdomen. Larvae that have siphons will hang downwards from the surface of the water with the siphon at the surface. Larvae without siphons will rest parallel just below the surface. Siphons can be long and thin like in the image on the left below, or they can be stubbier and more cone-shaped.

Siphon

No siphon

Thorax

Thorax

Abdomen

Head

Head

Abdomen

Photos: Rebecca Brown

The presence of a siphon is a sure sign that the larva is a mosquito, but the absence of one doesn't necessarily mean that it's not a mosquito. Other clues that you have a mosquito larva are:

  • An abdomen that is visibly narrower than the head/ thorax. The abdomen is the long segmented section at the bottom of the mosquito. Some other types of insect larvae do not have a clear distinction between the abdomen and the rest of the body, making them look worm-like in appearance. Mosquito larvae usually have a head and thorax (the middle section of the body) that is broader than the abdomen. In some species, this gives them a shape a bit like a lollipop!

  • Long hairs on the sides of the body. This might not be obvious to the naked eye, but should be visible under a magnifying glass.

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