Mosquito lore

Why are mosquitoes religious?

Because they prey on you! The unpronounceable Aedes aegypti mosquito is worse than most: yellow fever, dengue fever, chikungunya, and now Zika, which has spread to more than 50 countries.

The species was first named Culex aegypti in 1757 by the Swedish naturalist Fredric Hasselquist, whose mentor, Carl Linnaeus, lacked information about the natural history of Palestine. The unfortunate Hasselquist set off for Asia Minor, Egypt, and Cyprus, but succumbed to travel fatigue and died near Smyrna on his way home. Linnaeus later published the account of his trip in Voyages and Travels in the Levant.

Interestingly, Hasselquist speaks not of mosquitoes but of Gnats: “They were a different sort from those we have in Europe, being less; but bit worse, and left great boils in the skin, with an intolerable itching in the place they bit. They are quite different from those I saw at Alexandria, which were as large as we have them in Sweden, but of a different colour, namely ash-coloured with white spots on the joints of their legs.”

Perhaps they were not gnats but Aedes aegypti. Today, commerce, travel and global warming are helping the mosquito to flourish in places where it was previously unknown. In “Mosquitoes on the move” (Science, 25 November 2016), Jeffrey R. Powell, professor of ecology and evolutionary biology at Yale University, says that “These expansions are putting at risk large human populations that never experienced aegypti-borne viruses and therefore have no immune defences against them… greatly increasing the likelihood of severe epidemics.”

There are two subspecies of A. aegypti – the human-loving “Aaa” and the “Aaf” form traditionally found in forests – which are now interbreeding from Argentina to Africa. The consequences of increasing hybridization are unclear, although increased genetic variation could make the mosquito more resilient.

A. aegypti is able to adapt, evolving to thrive and survive in densely populated places, particularly urban environments littered with old tires and open containers. It can breed in bottle caps. Its larvae don’t necessarily need water to survive and eggs can lie dormant for a year or more – only to hatch once submerged in water.

Mark Twain was more than familiar with mosquitoes. In Life on the Mississippi (1883), one of his characters tells a tall story about lawless mosquitoes seen trying to vote: “Noticing that this statement seemed to be a good deal of a strain on us, he modified it a little: said he might have been mistaken, as to that particular, but knew he had seen them around the polls ‘canvassing’.”

Mark Twain also found a way of getting rid of mosquitoes that may be useful in tackling today’s Egyptian plague. In the first volume of his Autobiography (1924) he tells how in Italy, “The mosquitoes are not a trouble. There are very few of them, and not much interested in their calling. A single unkind word will send them away; if said in English, which impresses them because they don’t understand it, they come no more that night.”

That should save the World Health Organization a heap of time and money.

aedes-egypti

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