DIPTERA > NEMATOCERA | Lower Diptera

CULICOMORPHA > Culicoidea > Culicidae (36 species)

(subfamilies: Anophelinae and Culicinae)

Mosquitos are small to medium-sized midge-like flies, typically around 4-9mm long with a slender body, long delicate legs and a pair of narrow, scale-covered wings. They have a comparatively small head with large compound eyes, complex mouthparts with a long protruding proboscis that differs in form between the sexes, and fifteen-segmented antennae, which in the female are long and pilose but, in the male, covered with hair-like, bushy whorls.

They go through a complete metamorphous, hatching from eggs into larvae, then pupating before emerging as adults. Both sexes feed on plant-based sugars, but the female has to supplement her intake with a blood meal, which is necessary for egg development. In most cases they will target animals or birds rather than humans, but there are a few species, such as the 'house mosquito' Culiseta annulata that you sometimes hear buzzing around your face at night, that are well-known nuisance biters. 

The need to extract blood has resulted in the female having a complex proboscis where six separate stylets are housed within a sheath-like labium; consisting two mandibles, two maxillae that are used to saw their way through skin, a hypopharynx and the all-important labrum that is used to suck up the blood, but which is initially curled back when the mosquito begins to bite, although always staying in contact with the skin to guide the stylets downwards before pushing itself into the opening.

When seen at rest, mosquitoes typically sit with their forelegs bent outwards, which is a useful way of avoiding confusion with similar looking Chironomids that characteristically extend their front legs forward.

Thirty-six species of mosquito have been recorded in Britain; six in the Anopheles genus, identifiable by their long palps which are about the same length as their proboscis; the remaining thirty, are all in the Culicinae subfamily, within six genera, Aedes, Ochlerotatus, Coquillettdia, Culex, Culiseta and Orthpodomyia.

Species are associated with specific aquatic habitats that are suitable for egg-laying and survival of the larvae. The adults generally don't disperse too far from these breeding areas, so the 'habitat type' is an important indicator and a good place to start when trying to identify particular mosquitoes. The most likely species can then be listed together with any other possible candidates. The rest can pretty much be ignored. There are six primary habitats, ranging from temporary saline or freshwater pools to permanent ground water, such as ditches, ponds or canals, to artificial or underground water sources.

An identification key can then be used to narrow down the options, but it's dependent on features that aren't always visible in photos and, from my limited experience, it's unlikely that you'll be able to take shots from all the required angles. Individuals tend to settle in awkward places where you may only be able to take a photo from one position.

After initially determining the sex, the key starts with the length of the palps. If they are as long as the proboscis the individual in question should be an Anopheles. If the wings have 'spots' it should be Anopheles maculipennis, but otherwise you would have to check for white scales on the head. If the palps are shorter, no longer than half the length of the proboscis, other features come into play, such as an evenly tapered abdomen with long cerci indicates an Aedes species. From there you need to be able to check distinctive characters, particularly any leg and/or abdominal markings.

Ochlerotatus annulipes and Ochlertatus cantans, formerly of the Aedes genus and often still listed as such in some literature, are two common species that can be found in shady areas of wet woodland. They are morphologically very similar and, in some cases, difficult to separate from photos, but with a good view of the pale-scaled annulations around the tarsi they can often be distinguished. In Ochlerotatus cantans these white bands cover only the proximal ends of each tarsomere occupying around a third of the segment, whereas in Ochlerotatus annulipes they are much broader and cover close on half the length. The arrangement and extent of the annulations is similar on each leg, but is best compared by looking at the hind tarsi. Each tarsus consists of five segments (tarsomeres), which get progressively smaller as you count down the leg to the foot. The first long segment has just a small white band below the 'knee' joint, but all of the others, apart from the fifth and final tarsomere of the forelegs which is entirely black, have distinctive patterning.

As a point of interest, Ochlerotatus cantans is one of the species most commonly associated with nuisance biting in the UK. In fact, it's probably the most troublesome mosquito we have after Culiseta annulata. It's very persistent as I can attest to and a known species for biting throughout the day as well as at dusk. Strangely, the same is said about Ochlerotatus annulipes, but even when kneeling down in the damp grass to try to photograph them I wasn't pestered, but subsequently, when I went to see what I could find at a particular spot in Ringwood Forest I was bitten numerous times by Ochlerotatus cantans within just a few minutes.

Another frequently occurring species in wet woodland, especially in areas where there are shady pools with decaying leaves in the bottom where the larvae can develop, is Ochlerotatus rusticus. The side view of the individual featured below does not provide the detail required to confirm identity, but it is the most likely species given the habitat, general appearance, size and, importantly, the absence of any pale banding around the legs.

The remaining two individuals are probably Ochlerotatus annulipes and Ochlerotatus rusticus respectively given that they were again photographed at Blashford Lakes in the same general area, albeit during a previous visit, but there's simply not enough detail to be sure. They're both females and they both have tapered abdomens with the first showing at least some white banding on the legs and the second clearly with none.

I guess that most people would prefer to avoid mosquitoes rather than try to photograph them, but they are an integral part of our wildlife fauna providing an important food source for many aquatic and terrestrial creatures and, as such, need to be featured on this website like any other species.

New family added, June 24 (v.1)