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Bionomics of culex

Bionomics is a branch of biology concerned with the relations between

organisms and their environment. The study on mosquito bionomics greatly

assists in tracking their population dynamics. All mosquitoes need water for

breeding and thus complete their life cycle. Thus, the study on its bionomics

assists in tracking the source of a mosquito problem. Mosquitoes are ubiquitous,

conquering almost all water bodies for breeding, but their behavioral differences

exhibit specificity in occupying numerous ecological niches in choosing their

habitats. The knowledge on the bionomics of various species aids in surveillance

and planning further control strategies.

Mosquitoes of the genus Culex can breed in a variety of breeding places

ranging from highly polluted cesspits to clear water pools and containers. They

can not only inhabit semi-permanent or permanent bodies of ground water, but

also live exclusively in leaf axils, tree-holes, rock-holes, and crab-holes. Few

species for instance Cx. quinquefasciatus exclusively show high tolerance to

organically polluted water. Most of the species are categorized by their preference

for permanent water, floodwater, transient water or artificial container and tree-

hole habitats. While some species use more than one type of habitat. Accordinglythe larval habitats are categorized into standing water (permanent and transient)

and floodwater (including natural and artificial containers as well as floodwater)

habitats.

The standing water are permanent or transient pools and species

habituating these aquatic bodies lay eggs either singly or in rafts on the surface of

standing water, brood several times annually and also survive harsh

environmental circumstances. The permanent water group includes the freshwater

marshes where Culex species like Cx. nigripalpus, Cx. salinarius, Cx. tarsalis,

Cx. erraticus and Cx. Peccatorwere found, lakes with floating or emergent plants

host larvae ofCx. salinarius, Cx. nigripalpus, Cx. erraticus, Cx. Peccator, and in

ponds for example the grassy woodland ponds or fluctuating ponds and sinkhole

ponds contain larvae of Cx. nigripalpus, Cx. quinquefasciatus, Cx. restuans, Cx.

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salinarius, Cx. erraticus, Cx. peccator, Cx. pilosus, Cx. territans. Culex mosquito

group constituting Cx. quinquefasciatus, Cx. tarsalis, Cx. restuans and Cx.

nigripa1pus are found in transient water group. These water groups are the salt or

brackish water ditches, borrow pits and canals are evaded by Cx. nigripa1pus, Cx.

quinquefasciatus, Cx. restuans, Cx. salinarius and freshwater drainage ditches

with Cx. nigripalpus, Cx. pilosus, Cx. erraticus, Cx. quinquefasciatus larvae

along with larvae of other mosquito groups.

Very few species occupy the flood water group. Cx. atratus, Cx. pilosus are found

in rain and flood water pools and Cx. nigripalpus breed in both the former and

the mangrove swamps. The artificial environment breeding mosquito groups

involve only few species like Cx. quinquefasciatus which can breed in tree holes,

Cx. stigmatosoma, Cx epidesmus and Cx. tarsalis in tree canopy, Cx. opisthopus

in crab holes and Cx. quinquefasciatus, Cx. restuans, Cx. salinarius, Cx.

nigripalpus in artificial containers. Cx. territans is the species that is found

habitating the streams although it is found in other waters also. Thus, a wide

variety of Culex species found occupying multiple habitats, illustrates the

complexity of the problem faced by control agencies.