**4. Life cycle of** *Aedes aegypti*

*Aedes aegypti* is geographically distributed in tropical areas and it breeds in artificially filled water containers such as drums, tyres, flower vases such as plastic food containers, tin cans and old motor parts [4]. *Aedes aegypti* is a holometabolous type of insect, going through complete metamorphosis meaning four developmental stages from egg to adult stage. Life span of adult can range from 2 weeks to about 4 weeks but it depends on conditions of environment. A female mosquito lay eggs for about 4–5 times during her entire life span and average number of eggs in single spawn ranges from 10 to 100 eggs. *Aedes aegypti* are found in three different polytypic forms: sylvan, domestic, and peridomestic. The domestic type usually breeds in urban habitats, mostly inside or around houses. The sylvan type is rural form which breeds in tree holes, normally in forests, and the peridomestic form generally lives in environmentallymodified regions as coconut farms and groves (**Figure 4**) [24].

As the spread of mosquitoes is concerned, it occurs by active flight (adult) and passive transportation (immature stages) through international trades. Successive waves of invasion of *Aedes aegypti* and *Culex pipiens* have been aided by commercial passages also from fifteenth century to onward. *Aedes aegypti* substituted *Aedes albopictus* in Asian countries during the twentieth century [25, 26].
