Migration of the insects

Billion Insectes migrates each year, some at small distances, others at intercontinental distances, comparable with those of the migrations of birds.

One knows since antiquity the migration of the Criquet pilgrim. That of certain butterflies, whose Monarque in the USA has been studied for several centuries, but the study of the migrations of insects permitted by the radioémetteurs (Radio-alignment) and of novel modes of marking and follow-up is recent.

It is important for the ecology of the landscape and entomology or agriculture, because the insects have important ecological functions, and can sometimes be ravageurs of the cultures or trees. The knowledge of the animal migrations is also an public health issue, because certain insects, increasingly resistant to traditional insecticides, can convey microbes or parasites, them-even possibly become resistant to antibiotics, or likely to become it.

The modifications of these migrations can be due to the human activities, the fragmentation of habitats and the climatic modifications related to the Greenhouse effect.

The example of the dragonflies

One had a presentiment of that at least certain species of Libellule S were migrating, but without knowing at which distances nor which routes.

A team associating the universities of Princeton and Rutgers recently showed that dragonflies migrate a little to the manner of the birds, while being a priori able to make more than 100 km/par week per good weather without wind. One is unaware of still their routes, but while following (by car and/or plane) during 6 to 9 days 14 dragonflies of the species Anax junius (Anax of June) captured in the New Jersey, and equipped with transmitter-radio miniaturized, one showed that they migrated a little to the manner of the birds (towards the south of the USA in autumn), some making the voyage of the North-East of the country until in Florida at a mean velocity of 12 km per day (up to 100 miles/day, while being weighed down by the transmitters). They take place of rest, and like the birds, they steal whatever the direction of the wind, by compensating for little their drift (in this case, but butterflies were observed or dragonflies tropical to carry out a rectilinear way with the top of the sea or a lake, of day, but are posed when the speed of the wind exceeds 25 km/h and/or in rainy weather. It would be the temperature which pushes them; they seem to take off only after two nights cold following one another.

The dragonflies being supposed appeared 285 million years ago approximately (almost of 140 million years before the birds) perhaps they were pionnières as regards air migration.

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