44

■Bio-mathematics, Statistics and Nano-Technologies: Mosquito Control Strategies

Figure

4.1:

Schematic

life

cycle

of

mosquitos

(Source:

www.mosquitoes.org/

LifeCycle.html).

either singly (Anopheles) or stuck together in floating rafts (e.g., Culex). In the tropics, the

eggs usually hatch within 2–3 days. Some species (e.g., Aedes) lay their eggs just above

the water line or on wet mud; these eggs hatch only when flooded with water. If left dry

they can remain viable for many weeks (Service 1993).

4.3.1

Eggs stage of mosquitos

One factor common to all mosquito species is that eggs are laid in association with free

water or on a moist surface. Eggs are white when first deposited, darkening to a black or

dark brown within 12−24 hours. Single eggs are about 1/50 inch(0.5mm) long and those

of most species appear similar when seen by the naked eye, one exception is the Anopheles

spp. (Figure 4.2 a) whose eggs have floats attached to each side of the egg (Harbach &

Kitching 2005). Eggs are laid singly by some species, such as Aedes albopictus (Figure

4.2 b) and others lay eggs together to form rafts such as Culex species (Figure 4.2 c).

The incubation period (time between when eggs are laid and when they hatch) may vary

considerably among species. Eggs of permanent-water mosquitos where eggs are deposited

on the water surface may hatch in 1−3 days depending on temperature. Floodwater species

deposit their eggs on moist soil or another wet substrate and have a wide variation in

incubation periods. These eggs will not hatch until submerged by rising water caused by

rainfall, melting snow in the spring, or other floodwater. Depending on the species and