The Wild Party: A Diary of Urban Entomology

The mosquito blood-meal

After the pupation of the aquatic larvae, adult mosquitoes emerge from their pupae and fly off to breed. This is a mosquito of the genus Ochlerotatus, and probably the species Ochlerotatus trivittatus (formerly placed in the genus Aedes). It is now found throughout the world.

Most mosquitoes feed by drinking floral nectar or the juices of rotting berries and other fruit. After mating, however, a female must obtain a rich dose of protein to finish the development of her eggs. For this, she seeks a large blood-meal from a vertebrate—in this case, from me. Sensitive readers should look away now.

After piercing the skin with her proboscis, she angles and explores until she nicks a venule or arteriole. Meanwhile, her salivary tube pumps out an anticoagulant that helps the flow of blood. When she has found blood beneath the skin, she holds still and, in the span of 90 seconds, distends her abdomen to grotesque proportions with as much blood as she can hold.

After withdrawing, she flies off tipsily, carrying blood amounting to two or three times her body weight. Then she finds a safe resting place. In a process taking at least 45 minutes, she releases the water content of the blood by passing it in pink droplets through her anus. After thus dumping needless weight, the mosquito flies away with proteinaceous solids in her gut that will nourish her eggs, which she lays in large numbers in rafts on the surface of water.

There are parts of the world where encouraging a mosquito to suck one's blood would be foolish: delivered in the anticoagulant saliva, mosquito-borne diseases such as malaria (carried by the genus Anopheles) and dengue fever (the genus Aedes) are serious problems in many tropical areas. Fortunately, the mosquitoes of my temperate latitude are almost totally harmless.

Mosquito larvae

All that mosquitoes require for breeding are warmth, a source of vertebrate blood, and a shallow puddle; and after they hatch, the aquatic larvae are not fussy about the tiny organisms and organic detritus they eat. The nutrients in this little pool of rainwater, for example, will do very nicely.

The larvae resemble little tadpoles: eating machines with just a head, a mouth, and a locomotive body:

After several days of feeding, the larvae will pupate in the water. The pupae float on the surface, but each has primitive vision and an appendage that can flick the pupa a short way under if its escape reflex is triggered by an approaching threat. The adult mosquitoes emerge after pupation of only a few days.

Life isn't all in the mosquitoes' favor, however. The eggs, larvae, and pupae make good food for many predators, from aquatic dragonfly nymphs to fish. In fact, the accepted natural measure for controlling mosquitoes in a garden that has ponds or pools is stocking them with goldfish, which eat mosquito eggs and larvae.