Mosquito Blitzkrieg

Mosquito Blitzkrieg

From earliest members of the human species to those living on the planet today, almost every person has been bitten by a mosquito. It is probable that mosquitoes originated sometime during the Paleozoic Era, at least 300 million years ago, when insects and land vertebrates first lived together. Bites may be inflicted on any vertebrate — bird, mammal, reptile, or amphibian — anywhere on the earth except in the driest deserts, on the highest mountains, and in the most remote midocean or polar regions.

Throughout history the mosquito has had a devastating effect on mankind. As vectors of disease it has been responsible for more human deaths than any other single form of animal life. On the other hand, the mosquito has protected many tropical and subarctic regions from invasion, since native populations were able to become resistant to its bite. Mosquitoes became their allies against newly arrived conquerors.

In the tropics almost 2,000 species of mosquitoes continue their war against mankind. They transmit more than one hundred diseases to humans, including dengue fever, filariasis, viral encephalitis, typhus, and elephantiasis, and heartworm to dogs. Malaria and yellow fever are the most widespread of their depredations; these two diseases have probably killed more humans than have all the wars in history combined. At least a million people still die from malaria annually, and untold millions are stricken.

Among microscopic parasites that require a human host, there appears to be an "old girl network" that recognizes the need for a carrier to man. For this purpose the mosquito is perfect. It is the female that does the biting, since she must have blood for the protein needed to produce eggs. This is the bite that releases the disease—transmitting organism into the new host.

The victim is often unaware of being bitten but certainly hears the attacking mosquito because her wings vibrate at a rate of 200 to 500 beats per second. The attack completed, she will fly off carrying about three times her normal weight in blood. The mosquito is now loaded with enough nutrients to produce up to 500 eggs, depending on the species. Mosquitoes lay these eggs in water that may be fresh, brackish, or salt but must be slow—moving or stagnant. They exploit every imaginable source of standing water from a pitcher to a pitcher plant, a tire rut to a discarded tire.

Veterans of jungle warfare during World War II will recall a constant fight against mosquito hordes, and many soldiers were afflicted with malaria or other mosquito—borne parasites. Those stationed in the jungles of New Guinea were often horrified by what seemed to be a solid wall of mosquitoes on the trail ahead. Mosquito repellent was ineffective because it was rapidly diluted by perspiration, so all the mosquitoes of the world appeared to hum while waiting for them.

Because of the tremendous diversity of habitats in the warm, moist climates, three—fourths of all mosquito species do live in the tropics and subtropics. Some tropical areas can claim more than 150 species within a square mile. The number of species drops dramatically toward the Arctic latitudes. In the United States there are about 170 species, about 70 in Canada and fewer than a dozen species in the Arctic.

Despite the scarcity of species, the greatest concentration of individual mosquitoes occurs in the Arctic tundra. In the short summer, thousands of square miles of melted snow and ice flood the tundra over—lying the permafrost. Here mosquitoes hatch in such enormous hordes that the sunlight is actually darkened. Life for both man and beast becomes unbearable at this time, and it is quite common for outdoor workers to be draped in mosquito netting.

The mosquitoes seem to sense that summer is short and that they must move quickly to propagate their race. Their swarming attacks on anything that moves are almost frenzied. Many cases of the human mind temporarily succumbing to the drone of mosquito wings have been documented.

Canadian researchers, in the interest of science, once exposed their arms and torsos to a swarming horde of Arctic mosquitoes. They reported an occurrence of more than 9,000 bites per minute. For an unprotected person this could result in the loss of half of his blood supply in just two hours. This, of course, suggests death from shock, but since no human deaths have been documented as a result of excessive mosquito bites, no one seems to have completed that experiment.

Scientists refer to such an attack as a mosquito blitzkrieg, a phrase borrowed from World War II that seems most appropriate. To the infantry soldier who had experienced New Guinea, it would appear that the "solid wall of mosquitoes" had been transplanted to the Arctic.

From the book: 
Our Fascinating Earth