*14.1.1* Anopheles *mosquitos*

as parasites. Adult flies of many pest species are invited to decomposing material (such as rotting offal of fish) and dung, wherever they may breed and feed. They might thus spread pathogenic organisms when these lay eggs on fish.

Biting flies are two-winged external insects that feed actively on the blood of vertebrate hosts in the morning or evening and at night or day, and their biting is of a considerable nuisance. Their irritating bites could transmit pathogenic organisms that cause devastating loss of human and animal lives. The biting insects suck blood from humans and animals, and their biting is of a significant annoyance. More importantly, they are carriers for a number of organisms producing diseases and result in expiries on a huge scale. The most significant set of biting Diptera is mosquitos that have a slender and long body, and needle-shaped long piercing mouthparts. Others comprise phlebotomine sandflies, blackflies, tsetse flies, biting midges, stable flies and horseflies (tabanids), which normally have smaller biting mouthparts and additional robust bodies. The last three sets as vectors of human

Mosquitos diverge from other biting Diptera in having long needle-shaped mouthparts, a long slender body and long legs. The wings occasionally have noticeable outlines of scales. The adult insects measure between 2 and 12.5 mm in length. Certain species bite at night or in morning and evening, whereas others feed out of doors or during the day time indoors. There are several important genera of mos-

Males of the numerous species do not suck blood but feed on plant juices. The females usually mate only once, but produce eggs at intervals throughout their life and so most female mosquitos require a blood-meal. The ingestion of a blood-meal and the coinciding eggs development take 2–3 days in tropics, however longer in temperate regions. The gravid females look for appropriate places to lay their eggs, afterwards which another blood-meal is taken and another batch of eggs is laid. This practice is repetitive till the mosquito perishes. The mosquito life cycle involves eggs that are laid mainly in water. In some species, eggs are laid signally, while in others, these are laid joined together in rafts. Dependent on the species, a female lays eggs between 30 and 300 at a time. Various species directly lay their eggs on water surface either singly (*Anopheles*) otherwise fixed jointly in floating rafts (*Culex*). Particular species (*Aedes*) lay their eggs just above the water link otherwise on wet mud and only when flooded with water these eggs hatch. If left dry, these can keep on viable for several weeks. Larvae (wigglers) hatch and feed on aquatic material, pupate (become tumblers) and eventually emerge as adults. Adult females

Among the mosquitos there are two groups that suck human blood and may transmit disease. The anophelines; the genus *Anopheles* is best known for its role in transmitting of malaria, but in some areas it can also transmit filariasis. The culicines comprise the genera *Aedes,* vectors of dengue, yellow fever and other viral diseases and from time to time of filariasis; *Culex,* vectors of filariasis and various viral diseases; *Mansonia*, transmitter of *brugian filariasis*; and *Sabethes* and *Haemagogus*, spreaders of yellow fever in forests of Central and South America. Mosquitos *Aedes*, *Anopheles* and *Culex* may be differentiated from each one by way as presented in **Figures 8**–**12**. The best valuable features to distinguish anophelines from other

quitoes and key genera include *Culex, Aedes* and *Anopheles.*

**14. Biting Diptera**

*Life Cycle and Development of Diptera*

disease are of limited importance [64].

may live for several months [65, 66].

**26**

**14.1 Mosquitoes (Culicidae)**

About 380 species of *Anopheles* mosquitoes occur around the world. Some 60 species are sufficiently attracted to humans to act as vectors of malaria. A number of *Anopheles* species are also vectors of lymphatic filariasis and viral diseases. Female and male adult mosquitoes may be distinguished from every one due to occurrence of antennae that is bushy in males than females. Genus *Anopheles* may be distinguish from whole others genera based on occurrence of clubbed palps within males, while non-clubbed in rest of species and lengthy palps in *Anopheles* female whereas small palps in all other females (**Figure 7**).

The most preferred breeding sites are pools, seepages, quiet places in slowrunning streams, rice fields, leaf axils of certain epiphytic plants and puddles of rainwater, but not artificial containers, except in the case of *Anopheles stephensi* Liston (**Figure 8**). The eggs are elongated, about 1 mm in length, have a pair of

**Figure 7.** *(a) Male antenna, (b) Female antenna.*

**Figure 8.** Anopheles stephensi*.*

lateral floats and laid singly on the water surface where these float until hatching that occurs in 2–3 days. The larvae float in a horizontal position at the surface, where these feed on small organic particles. In the tropics, the duration of development from egg to adult is 11–13 days. Some species feed mostly on animals, while others feed almost entirely on humans. Mosquitos *Anopheles*, are active between sunset and sunrise, and there are variations also in their liking for biting outdoors or indoors. The anophelines, which come in houses to feed habitually rest for a few hours indoors after feeding, then can leave for outdoor protected resting sites like burrows, vegetations, crevices and cracks in ground, trees or in caves and undersides of bridges. On the other hand, they may stay for the whole period indoors required to digest blood-meal and produce eggs. Once the eggs are fully developed the gravid mosquitos leave their resting sites and try to find a suitable breeding habitat [69–72].
