Mosquito Mysteries

Pessimists who fear that science is exhausting nature's mysteries can take fresh hope from a newly published book: The Natural History of Mosquitoes, by Dr. Marston Bates (Macmillan; $5). Mosquitoes punch holes in man; they pester him, keep him awake, infect him with deadly diseases. So well-financed scientists, determined to deal with mosquitoes, have studied them intensively for more than half a century, accumulating a vast amount of information. But, as Dr. Bates points out, they have hardly begun to find out how even the best-known species go about their business.

The feeding habits of mosquitoes (their most intimate contact with man) are still poorly understood. Scientists agree that the males puncture only plants, but they are not sure which plants, for they rarely catch them at it. In some species, the females bite warm-blooded animals whenever they get the chance, but they can also thrive on vegetable food only.

Go to the Ant. The genus Harpagomyia preys on ants. The mosquito alights in front of an ant and holds it tightly with its forelegs. After a while the ant opens its mouth. The mosquito inserts its proboscis and sucks up food which the ant squeezes from its stomach. Both parties seem to enjoy this interchange. The mosquito vibrates its wings with pleasure; the shmoo-like ant caresses the mosquito's proboscis with its palpi.

Though mosquitoologists have turned up many such fascinating tidbits, they have not yet found what attracts mosquitoes to their human victims. It is not sight, for mosquitoes are almost blind. It is not odor; no odor, human or otherwise, seems to attract mosquitoes. Temperature may have something to do with it. A glass cylinder filled with water at blood heat is often attacked by swarms of hungry mosquitoes. A moist towel heated electrically gets the same attention. Some investigators think mosquitoes are attracted by carbon dioxide in the human breath. But neither theory explains how mosquitoes find their victims at a distance.

The sex habits of mosquitoes, though closely studied, are still a dark mystery. The males of a few species take their mates where they find them, just like less subtle insects. Among the Opifex fuscus of New Zealand, the males like their females young. They skim along the surface of stagnant water, watching downward intently and sometimes thrusting their heads below the surface. They are looking for female pupae about to become adult. When a pupa breaks the surface, the male tears open the pupa case and mates with the still-soft imago before it has fully emerged.

Male Swarming. Most mosquitoes are less direct. Their mating habits center around a curious custom that scientists call "swarming." Hundreds of males gather 'in a dim-lit space, whirling around & around one another, emitting a low hum. This, according to one theory, excites and attracts the females. Certainly any female that comes near the swarming males is never the same again. Some observers claim to have seen the same female join the same swarm repeatedly.

But often no females show up, though the males dance and hum their best. This has led to another theory that swarming is merely a device to brief the males and encourage them. After the dance is over, presumably, the males sally forth, full of enterprise, to hunt for mates.

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