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2.2.2. Anopheles larvae and pupae

Eggs

Mosquito females lay between 30-300 eggs in each oviposition. Eggs are brown or blackish and about 1 mm long. They are usually boat-shaped in anophelines, with characteristic lateral floaters. Eggs are usually laid single and float on water. In the tropics, eggs hatch in 2-3 days. Eggs are unable to survive dessication, but may survive a few days in soft mud.

Typical anopheline eggs : the eggs are usually laid single and float on water

Typical anopheline eggs : the eggs are usually laid single and float on water

Enlargement of an anopheline egg

Enlargement of an anopheline egg

Credits : Hilary Hurd

Typical egg of Anopheles showing the characteristic lateral floaters

Larvae

  • Mosquito larvae can be distinguished from all other aquatic insects by being legless and having a bulbous thorax that is wider than both the head and the abdomen.
  • All mosquito larvae require water in which to develop. They have to undergo 3 moults (i.e. there are 4 instars larvae). Mosquito larvae feed on yeast, protozoa and micro organisms. In contrast to the larvae of other mosquito genera, Anopheles larvae are surface feeders. In tropical countries, larval development (from hatching egg to pupation) requires between 5-14 days. In temperate areas, larval development may take several weeks or months, and some species overwinter in the larval stage.
  • For a detailed description of the morphology of larvae, showing the features used for taxonomy, go to the unit Morphology of larvae. The main feature that distinguishes Anopheles larvae from the larvae of other mosquitoes is the lack of siphon in Anopheles.
Aquatic larvae of Anopheles. Note the distinctive position with respect to the water surface

Credits : Image collection, LSTM

Aquatic larvae of Anopheles. Note distinctive position with respect to the water surface

Pupae

Pupae do not feed, but spend most of their life at the water surface taking in air through their respiratory trumpets. This is, however, a stage where major changes of internal organs take place, where the insect looses its specific larval organs and internally develops its adult organs, including legs, wings and biting mouth parts. Pupal development takes 2-3 days in the tropics. At the end of pupal life, the skin on the dorsal surface splits and the adult mosquito struggles out.

Pupae spend most of their life at the water surface taking in air through their respiratory trumpets.

Pupae spend most of their life at the water surface taking in air through their respiratory trumpets.

Credits : Image collection, LSTM

Anopheles pupae at the water surface, breathing through their respiratory trumpets.



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