InfluentialPoints.com
Biology, images, analysis, design...
Clegs etc Ticks Mossies Tsetse
"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

 

 

Family Culicidae (Mosquitoes)

Very slender flies with an elongate piercing proboscis, stiff palpi and no ocelli. Legs are long and antennae are plumose in the males, pilose in the females. Wings are fringed with scales along the posterior margins and veins. Maxillary palps of the female may be as long as, or longer than the labium (subfamily Anophelinae) or much shorter than the labium (subfamily Culicinae).

Biology & Disease Transmission: The enlargement shows the mouthparts. The paired mandibles and maxillae lie around the tube-like labrum to form the stylets (showing bright red here as the blood is sucked up). When not biting, the stylets are enclosed by the labium (the sheath curving down below the stylets). When the mosquito bites, the pointed and barbed maxillae penetrate the skin and anchor the mouthparts in the tissue. The sheath like labium slides back and the stylets pass through its tip and into the tissue. Saliva containing anticoagulants is injected through the hypopharynx. Blood is then sucked up through the labrum.

Mosquitoes are important vectors of disease including yellow fever and dengue fever, transmitted mainly by Aedes aegypti, and malaria, transmitted by Anopheles spp. The recently emergent West Nile virus is mainly transmitted by various Culex species.

Genus Anopheles

Adults are slender insects with head and abdomen oriented in a straight line at an angle to the surface when at rest. The maxillary palpi are about as long as the proboscis and in males are clubbed at the end. The scutellum posterior margin is evenly rounded. Abdominal segments usually have only small patches of scales or none at all. Larvae do not have a siphon. They live in a variety of aquatic habitats but predominantly in ground waters. The larvae feed at the water surface Adults of most species are nocturnal or crepuscular, resting in cool damp places during the day. They feed on the blood of warm-blooded animals.  

Anopheles plumbeus

The adult has white scales on the head and lacks clearly defined patches of dark scales on the wings. The pleurites of the thorax and lateral parts of the scutum are blackish brown forming a distinct contrast to the ashy grey median part of the scutum which has narrow to moderately broad pale spatulate scales. (The similar Anopheles claviger has the pleurites of the thorax and lateral parts of the scutum fawn brown or light brown, hence not contrasting sharply with the median part of the scutum.) The antennae have numerous long flagellar whorls and the scales on wing veins are dense. The wing length is at most 5.0 mm.

Anopheles plumbeus breeds almost exclusively in tree holes, and is known to bite frequently in daytime. It is present over much of Europe and parts of Asia and the Middle East and readily attack humans. Anopheles claviger has a much wider range of breeding sites including clean, dirty, or brackish water in ditches, streams, ponds, and rain barrels.

This mosquito was found commonly in woodland at Ebernoe Common in West Sussex, UK where they were biting (us) vigorously! We cannot be certain that it is Anopheles plumbeus rather than Anopheles claviger, but both are of interest since they are potential malaria vectors. Until recently in Europe more work has been done on Anopheles claviger since is a known malaria vector in the Middle East. For example Service (1973)  showed that Anopheles claviger had two generations per year in southern England with maximum biting densities in May and September.

There is renewed interest in Anopheles plumbeus following a strong population expansion all over Belgium creating a severe nuisance at a local scale. Dekoninck et al. (2011)  has suggested this is the result of a recent larval habitat shift of this species from tree-holes in forests to large manure collecting pits of abandoned and uncleaned pig stables. Moreover, Schaffner et al. (2012)  have shown that the species is receptive to the malaria parasite and hence increases the malaria transmission risk in Central-Western Europe.

Genus Culex

Adults are rather drab coloured insects, although some species do have markings on the legs and wings similar to Anopheles. They have distinct pulvilli (pads) at the ends of the legs and have no prespiracular or postspiracular setae. The maxillary palpi are shorter than the proboscis . Larvae have a siphon. They live in a variety of semipermanent or permanent bodies of ground waters as well as leaf axils, tree holes and artificial containers. Adults of most species are nocturnal. They feed on the blood of warm-blooded animals including humans, as well as on amphibians and reptiles.  

Culex pipiens (Northern House Mosquito)

Adults of the Culex pipiens complex are light brown mosquitoes that lack distinctive markings on the proboscis and legs. Adult females of the complex are usually identified by the presence of distinctive, basal, pale abdominal bands which are broadly rounded medially and distinctly constricted sublaterally before joining large, lateral scale patches. Adult males also have pale abdominal bands but they are not diagnostic. Larvae of the Culex pipiens complex can be identified by: the presence of a moderately long siphon that has 6-13 pecten teeth located on the basal third, and 4-branched siphonal tufts, one of which is inserted laterally and out-of-alignment with the other three.

Members of the Culex pipiens species complex include Culex pipiens (the northern house mosquito), Culex quinquefasciatus (southern house mosquito) and Culex australicus. In addition the subspecies Culex pipiens pallens occurs in Far East (as well as Mexico and parts of the USA) and the hybrid Culex pipiens Culex quinquefasciatus is common in the USA. There are also several very similar species not now formally included in the complex such as Culex torrentium which is present over much of Europe. The situation is further complicated by Culex pipiens having two distinct forms. Form pipiens diapauses, requires a blood meal to lay eggs, is unable to mate in confined spaces, and mainly feeds on birds. Form molestus is active all year round, lays its first batch of eggs without a blood meal, mates in confined spaces and feeds on both birds and mammals especially humans. Form pipiens is widespread but form molestus is mainly confined to urban sites such as deep mines and underground railway systems in northern Europe which offer shelter from adverse winter conditions. Members of the Culex pipiens species complex transmit the viruses responsible for various types of encephalitis including West Nile virus, and also of Wuchereia bancrofti which causes lymphatic filariasis throughout the tropics.

Our first picture above shows a male of the Culex pipiens species group reared from larvae found in a water container outdoors in September in UK. Male characteristics include plumose (feather-like) antennae and long feathery palps about as long as the proboscis. Species group characteristics are the light brown colour with six basal pale bands on the abdomen and no distinctive markings on the proboscis or legs. The specimen pictured is most likely Culex pipiens, although Culex pipiens and C. torrentium are morphologically similar and can only be reliably distinguished using characters of the adult male genitalia. Its outdoor breeding site strongly suggests the bird-feeding form pipiens.

 

These two pictures show female Culex pipiens reared from the same batch of larvae as the male. Unlike the males, the antennae are pilose (with only a few short hairs) and the palps (visible in the second photo above) are much shorter than the proboscis. We were unable to get these Culex pipiens females to accept a human feed, consistent with them being bird feeders. They are one of the prime suspects of arbovirus transmission between birds.

 

Culex pipiens form pipiens breeds in a wide range of sites including ponds, marshes, ditches, tree holes, and containers such as tanks and butts. The water may be fresh or brackish, clean or foul, and with or without overhanging or emergent vegetation. The first picture above shows a final instar larva of Culex pipiens, one of many found in a water container filled with rainwater in a rural East Sussex garden. It is filter feeding with its mouth brushes. Note the rather long siphonal tube - this is an extension of posterior spiracles and is used as a breathing tube by the larvae of Culicine mosquitoes. The second picture shows a pupa of Culex pipiens- the pupa takes oxygen through two breathing tubes at the front of the head called trumpets. The pupa does not consume food, but if disturbed it can dive in a jerking tumbling motion before it floats back to the surface.

The Culex larva in the image above appears to be using the feeding current generated by the mouth brushes to glide slowly through the water as described by Brackenbury (2001). 

 

Genus Culiseta

Adults are rather large mosquitoes which superficially resemble Culex. The maxillary palpi are shorter than the proboscis. They lack pulvilli, but have prespiracular setae and possess a diagnostic patch of setae at the base of the subcosta on the ventral surface of the wing. They live in ground waters such as bogs, marshes and streams with a few species breeding in tree holes and rock pools. They feed on the blood of birds and mammals and a few feed on reptiles.  

Culiseta annulata (Banded house mosquito)

The costa is largely or entirely dark scaled and the wing has distinct dark spots. The legs and abdominal terga have a contrasting pattern of dark and pale scales. A widespread and often common mosquito in Western Europe and parts of the Middle East. It breeds in natural and artificial waters, sunlit or shaded areas, and fresh or brackish water. Adult females feed both indoors and outdoors on a variety of hosts including humans and birds.

This picture shows a female Culiseta annulata found inside the house during a mild spell in February. She attempted (unsuccessfully) to get a blood meal from the occupant. The contrasting pattern of dark and pale scales on the legs is clearly shown. The picture below shows the same specimen preserved and mounted to show the pattern of markings on the wing and abdominal tergites.

The wing costa (leading marginal vein) is mainly dark-scaled with isolated pale scales. There are four or five distinct dark spots on the wing caused by dark scales. White or yellowish scales on the abdominal tergites are restricted to basal bands and a longitudinal band on tergum II. Although this image was taken in mid-summer, this species is often responsible for nuisance biting early and late in the year. Culiseta annulata is a cold adapted species able to overwinter without the need for diapause.

Whilst the bites are irritating, the species is not known to transmit malaria. However Medlock et al. (2007)  reports that it is a known carrier of several arboviruses, and is a potential vector of West Nile virus. Hatherly et al. (2009)  found the species breeding in water pools in old tyres on several tyre disposal sites in the West Midlands in Britain. They recommended that, to reduce mosquito numbers, tyres at the perimeter of storage sites should be treated with insecticide.

Genus Ochlerotatus

The palps are about one third to one quarter the length of the proboscis. The thorax is usually dark grey to dark brown or blackish, and the scutum is covered in scales. Prespiracular setae are absent. The legs are mostly covered with dark scales, but pale scales may be scattered or grouped to form a knee spot or basal or apical rings. Pulvilli are setous or inconspicuous. Wings are predominantly dark scaled. The abdomen has elongated cerci and appears pointed because of the narrowed last segments. The scaling of the abdomen is extensive with various patterns of banding. The genus was formerly treated as a subgenus of Aedes (and some still consider it this way).  

Ochlerotatus cantans (Woodland mosquito)

In this species the white bands on the tarsi cover only the proximal ends of each tarsomere occupying about a third of each tarsomere (this distinguishes from Ochlerotatus annulipes bands where the white band covers nearly half of each tarsomere). The outer surface of the hind-femur is fairly evenly sprinkled with dark scales though proximally and ventrally they are not so numerous as distally and dorsally. The wings have a pepper-and-salt appearance due to a mixture of light and dark scales.

This mosquito was previously misidentified on our website as Culiseta. However, it is clearly belongs to the Ochlerotatus/Dahlia group given the (apparent) pointed shape of the abdomen. Species identification is difficult as we cannot see the dorsal surface of the abdomen, but we have tentatively identified it as the common woodland mosquito Ochlerotatus cantans.

 

Family Ceratopogonidae (Biting Midges, no-see-ums)

Small or very small flies; antennae plumose in male, pilose in female; head not concealed by thorax, thorax without a V-shaped suture; ocelli absent; mouthparts of female adapted for piercing but not in the form of long slender piercing stylets; maxillary palps 3-5 segmented & drooping; fore legs not elongate; wing costa not extending around entire wing; wings folded one above the other and held over the body when at rest.

Biology & Disease Transmission: Adult biting midges are usually ectoparasitic feeding on blood. Females of the genus Culicoides feed on the blood of vertebrates. Females of most other genera including Forcipomyia and Atrichopogon feed on the blood of large insects.

 

Atrichopogon (Meloehelea)

Adults of the subgenus are distinguished by the following combination of characters: sensory pit located at midlength of third palpal segment; eyes bare; wing membrane with macrotrichia in both sexes; two seminal capsules; female lacinae smooth or with 6-15 teeth. Species identification of midges feeding on insects is somewhat problematic. Mann & Turner (2003)  reported Atrichopogon (Meloehelea) winnertzi as feeding on Meloe violaceus in UK. However, Szadziewski et al. (2007)  have stated that all reports of this species feeding on Meloid beetles are misidentifications. In Poland they identified seven other Atrichopogon species all feeding on Meloidae. We make no attempt to assign a species name to the ones we have photographed.

These midges were seen attacking a blister beetle (Meloe violaceus). If attacked by a predator, these beetles exude a blistering fluid which contains cantharidin. The midges are thought to use the odour of cantharidin to find their host. In this image they can be seen feeding at the thin intersegmental membranes of the beetle.

Identifications & Acknowledgements

Whilst we try to ensure that identifications are correct, we do not warranty their accuracy. We have mostly made identifications from our photos of living specimens. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. Most of the taxonomic information on families is summarized from Richards & Davies (1977) . Becker et al (2003)  was used for mosquito identification. Information on the distribution and biology of mosquitoes in the UK was obtained from Snow (1998) , Health Protection Agency (2009)  and Medlock & Vaux (2011) 

References

  •  Becker, N. et al. (2003). Mosquitoes and their control.Springer.

  •  Brackenbury, J. (2001). Locomotion through use of the mouth brushes in the larva of Culex pipiens (Diptera: Culicidae). Proceedings of the Royal Society B 268, 101-106. Abstract   Full text 

  •  Dekoninck, W. et al. (2011). Human-induced expanded distribution of Anopheles plumbeus, experimental vector of West Nile Virus and a potential vector of human malaria in Belgium. Journal of Medical Entomology 48 (4), 924-928. Abstract 

  •  Hatherly, I.S. et al. (2009). Mosquito breeding in tyre disposal sites in the West Midlands.Journal of Environmental Health Research 9 (1). Full text 

  •  Health Protection Agency (2009). Mosquito Recording Scheme: Species Profiles. Full text 

  •  Mann, D.J., & Turner, C.R. (2003). Atrichopogon (Meloehelea) winnertzi Goetghebuer (Diptera: Ceratopogonidae) feeding on Meloe violaceus Marsham (Coleoptera: Meloidae). British Journal of Entomology and Natural History 16, 7-9.

  •  Medlock, J.M. et al. (2007). Possible ecology and epidemiology of medically-borne arboviruses in Great Britain. Epidemiology and Infection 135, 466-482. Abstract  Full text 

  •  Medlock, J.M. & Vaux, A.G.C. (2011). Assessing the possible implications of wetland expansion and management on mosquitoes in Britain.European Mosquito Bulletin 29, 38-65. Full text 

  •  Richards, O.W. & Davies, R.G. (1977). Imms' General Textbook of Entomology. 10th Edn. Chapman & Hall, London.

  •  Schaffner, F. et al (2012). Anopheles plumbeus (Diptera: Culicidae) in Europe: a mere nuisance mosquito or potential malaria vector? Malaria Journal 11, Full text 

  •  Service, M. (1973). The biology of Anopheles claviger (Mg) (Dipt., Culicidae) in southern England.Bulletin of Entomological Research 63, 347-359. Abstract 

  •  Snow, K. (1998). Distribution of Anopheles mosquitoes in the British Isles. European Mosquito Bulletin 1, 9-13. Full text 

  •  Szadziewski, R. (2007). European Atrichopogon biting midges of the subgenus Meloehelea (Diptera: Ceratopogonidae). Polish Journal of Entomology 76, 267-284. Full text 

Last updated 17 January 2013