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Aedes aegypti is a domesticated mosquito with a short flight range, and urban spread of dengue is frequently house-to-house in a contiguous manner. The mosquito breeds in tropical or sub-tropical climates in man-made water-holding receptacles in and around human habitation, or in tree holes or plants in close proximity to human dwellings. These sturdy urban survivors are found in nearly every major city in the tropics, as well as in the sub-tropics, and they apparently prefer the blood of humans to that of other animals. Aedes aegypti has four stages in its life cycle with the first three (egg, larva, and pupa) played out in water. However, in the fourth stage, the adult is a flying arthropod equipped with sucking mouthparts to feed on human or animal blood or on plant juices and it seeks an aquatic environment in which to reproduce. Aedes aegypti eggs are laid singly on the surface of water or in clusters called rafts. Eggs of some species of mosquitoes may be laid on moist ground subject to periodic flooding (they lay dormant until flooding occurs) when the larvae emerge to live in water; different species have adapted to exploit almost every aquatic environment. The larvae molt four times in, at least, a ten-day period, which culminates in the pupal stage. Both larva and pupa are active stages, yet unlike the larva the pupa does not feed. The pupal stage lasts from one day to a few weeks, after which the adult emerges from the pupal skin. The emerging adults are small and fragile with one pair of narrow wings, three pairs of long, thin legs, and a slender abdomen.  Interestingly, only female mosquitoes bite and the females of most species require a blood meal before they are able to lay fertile eggs. While the primary environment of the adult mosquito is the air, they consistently mate while airborne, rarely are they encountered in large numbers far from their aquatic breeding sites suitable for egg laying.