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Eggs
 Mosquito eggs are generally
cylindrical with an approximate length of one millimeter. They are
laid individually (Ochlerotatus , Anopheles) or in groups
named eggrafts containing 50 to 200 items (Culex, Culiseta).
The shape of the eggrafts prevents them from sinking; in certain
cases of individual eggs, this is achieved by floating devices (Anopheles).
In another genus (Ochlerotatus ), the female lays the eggs
in dry substrates such as the ground of a salt marsh, where they
remain inactive. In such cases, egg hatching is related to environmental
events, such as flooding.
 All
mosquito larvae are aquatic. Their life cycle comprises four development
stages with corresponding moults. In this time, they grow from a
mere 1 mm in length to around 12 mm (depending on species). The
length of the cycle is closely related to water temperature. In
the Llobregat delta the Culex pipiens larval development can be
as short as 5 to 7 days in summer, although it can be much longer
in lower temperatures. Larval movement is achieved by characteristic abdominal movements. The larvae feed upon small organic material such as algae and bacteria. They can act as filterers and sediment browsers. In most species, the larvae breathe atmospheric oxygen using a siphon, located in the abdomen, which they use at the water/air interface when in a normal inverted position. The larvae of species from the genus Anopheles have no siphon, and thus they remain just above the water surface and breathe directly through the abdominal spiracle. In some species in the genus Coquillettidia, mobility has been lost and they have adapted a modified siphon that they hook to subaquatic plants, thus breathing through the parenquima of the plant.
 The
changes that allow the mosquito to shift from an aquatic to an aerial
evironment begin at the end of the fourth stage with the initial
muscle lysis, and continue through the metamorphosis into the pupal
stage. The pupal stage lasts for 2 to 3 days, during which no feeding takes place, but rather pupae survive on the nutrients they have accumulated. They breathe through two respiratory trumpets located on the cephalothorax, and are much more active than other insects. Although they remain in a resting position at the water's surface, they can dive and move very quickly due to the contraction of their abdominal paddles. At the end of this stage, the exoskeleton is longitudinally broken, the adult takes in as much air as possible, and abandons the pupal shell. It rests for a while on the water surface before taking off for its first flight.
 Adult
mosquitoes both male and female, usually feed on sugary substances
such as flower nectar. However, mosquitoes are well known blood
suckers because females need blood as a nutritional protein supplement
for egg laying. The females of several species can fly for very
long distances seeking the blood they require. Mosquitoes are vertebrate parasites but can show trophic preferences for certain orders. Some species prefer birds (Culiseta longiareolata) or amphibians (Culex hortensis). Other species such as Culex pipiens can produce a first egg batch without having had a blood meal. This phenomenon is called autogeny and it is possible thanks to the nutritional reserves of the larva. Most mosquito species bite at certain times of the day, typically at dusk and dawn. Some species, however, such as many Ochlerotatus , bite throughout the day in the Baix Llobregat. Each female generally mates only once, shortly after emergence from the pupal shell. Mosquitoes can, like other species, mate in swarms without having to stop flying. The male sperm is retained by the inseminated female in the spermatheque from where it fertilizes the eggs on being laid. The number of eggs laid depends on the species and the amount of blood that the female has fed on. One bite may well provide the necessary blood for an egg batch, and the female will not bite again until it has been laid.
Winter hibernation can take place during a specific stage (egg, larva or adult) or during two or more stages; however, the most common hibernating stage is that of the the adult female. These mosquitoes obtain all the nectar they can in order to produce a special organ, the fat body, which provides nutrients during the cold period. The females then seek shelter and suspend their metabolic activities, whereas the males simply die. An adult mosquito can have a lifespan ranging from just a few days to a couple of months, depending on the species and the climate.
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