Everyone knows what mosquitoes are, bothering us with their buzzing and painful bites. The name actually refers to over 3.000 species of diptera (including flies and horseflies as well), characterized by the presence of only two wings, while the other, club-shaped pair, have a sensory function only.
Mosquitoes belong to the genus of Culicoides and their life is closely intertwined with that of man, since most females feed on the blood of humans or domestic animals. When the female pricks man or another animals, it injects some of its saliva, so if it happens to be carrying parasites, these can infest the unfortunate “victim”. These insects have been the object of many studies, since they transmit a great number of diseases .
Mosquito eggs need water in order to develop; females lay their eggs in rivers and in stagnating water contained in recipients – for instance saucers, tree cavities, etc. Some species, such as Aedes, lay eggs on mud or damp ground; eggs belonging to these species resist to drying even for years, hatching when environmental conditions become favourable.
Mansonia mosquitoes lay their eggs on the underside of acquatic plant leaves. Eggs are lain in a raft-like structure and each aggregation can contain up to 400 eggs. After hatching, larvae disperse, feeding on fragments of organic substances; larvae breathe thanks to the presence of a thin tube allowing them to source oxygen present in the atmosphere. Larvae feed on organic debris, bacteria, protozoa, algae; subsequently, they transform into pupae and as such remain for 2 – 3 days. Finally, after about one week after hatching, they become adults, ready after 2 – 3 days to start a new lifecycle. Only females feed on warm-blooded animals, whereas males prefer nectar and plant sap. Males present long, frayed antennae, capturing vibrations coming from females. In Italy, mosquitoes belonging to Culex and Aedes genuses are very common.
Mosquitoes belonging to the Aedes genus have only recently reached Italy. Smaller than common mosquitoes, it is of Asiatic origin, characterized by being black with white stripes on their legs and abdomen. Known as the tiger mosquito, a very aggressive animal causing swelling and blisters when it bites: so far it hasn’t caused any particular diseases. The Culex genus is ubiquitous and many species are known as “house mosquitoes” since, similarly to the Aedes genus, they develop in recipients containing stagnating water, located close to houses. The animal can transmit viral encephalitis and, in tropical and subtropical climates, filariasis. During Summer in 1999, around Queens and New York they transmitted the so-called West Nile virus, which causes a serious form of encephalitis in man and domestic animals.
How to defend oneself from moquitoes?
The most widely used chemical substance worldwide to keep mosquitoes at a distance is diethyltoluamide (D.E.E.T.); present under false name in some insect repellant products for environments or explicitly mentioned in various lotions, sprays, sticks and body creams, D.E.E.T. is very effective in keeping mosquitoes away, as it is toxic for man. Dozens of studies and publications carried out worldwide prove that D.E.E.T. is poisonous for man, to the point that ingestion of liquid contained in a bottle (60% is sufficient) and based on this substance is lethal also for healthy adults: typical symptoms are convulsions, hallucinations and coma, occurring within an hour following ingestion.
Given that ingestion can only be accidental, what’s however particularly worrying are the potential consequences deriving from systematic topical use. A published study has proved that a child was born with facial deformities and mental retardation due to the fact that the mother used a D.E.E.T. based insect repellant during pregnancy.
Diethyltholuamide is therefore a substance to be used with caution and this is clear from the warnings that manufactures are obliged to mention in the labelling of their products: “do not drink or smoke during application, do not apply on newborn babies, use on children with caution, …”; among these warnings, one in particular catches the eye: “do not spray on varnished surfaces or plastic materials (this is all the more paradoxical, given that the product to be applied on the skin should be “gentle” and not corrode plastic!).