Culex pipiens
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Consider the most common mosquito on earth, one that is likely resting in some dark corner of your very own home or, if you are reading it during warm summer evening, you are about to issue its faint buzz – do you hear it right now? – in your ear.
This soft, dusty brow insect with a body less than a quarter inch long, is probably Culex pipiens, one of more than 2,500 different species of mosquitoes. You’ve seen her land on your arm. You have caught her just at the end of feeding, her translucent belly swelling red with your blood. At such a moment, you can be forgiven for failing to notice what an elegant and hardy thing she is. But she is.
The scientific mission was accomplished with the help of a shiny spoon attached to a stick which, once places over the water. It seemed to attract mother mosquito who then began over positing in flight, like a tiny dive bomber.)
Secure in the raft, each Culex pipiens mosquito embryo develops with its head down, resting against a line of fracture encircling its shell. The entire incubation process take just two days, and at the end, often nearly in unison, the grayish white larvae burst outward by the hundreds. They emerge as long, segmented, wriggling larvae with whiskered heads that hang down in the water for feeding and tails equipped with a breathing tube that takes in air at the surface of the water.
All of the worlds insects as well as all arthropods, including crabs and lobsters, are descended from a single segmented ancestor, a warmish creature called an onychophoran. Onychophora, which still crawl the planet today, are made of more than a dozen similar segments, each with a pair of stubbly legs. An onychophoran possesses a mouth, which is always open, a simple gut, and an anus at its terminal end.
Though it is sometimes difficult to see, especially in crabs, all arthropods share onychopphora’s segmentation. It is quite evident in a mosquito larva, which has a wormlike abdomen but is also equipped with a thorax and a well formed head with eyes and elaborate mouth. The mouth includes a pair of mandibles for chewing, a pair of laterally mounted maxillae for grasping, and upper and lower lips known as the labrum and the labium.
Beyond the head, three segments of the larva’s thorax are ornamented with hairs, which the larva uses to stabilize itself in the water. The terminal group of segments bears the air tube, or siphon, through which it breathes. Nearly all larvae drift through life with this tube, located on their rears, poking up against the surface of the water where it can take in air.
If Culex pipiens and all the other mosquitoes never developed beyond the larval stage they would still be beautiful and fascinating animals. To the naked eye, they seem to float peacefully, their bodies hanging down from very surface of the water. Under magnification, they can appear as fierce as any monster in an outer space movie, with large eyes, spiky whiskers, and hungry mouths.
Among the thousands of species of mosquito that have been names there are many variations on this beginning to life. One, Wyeomyia smithi, will develop only in the water that collects in North American pitcher plants. In the same bogs where the pitcher plants grow, a mosquito called Coquillettidia pertubans has a truly bizarre way of finding its air supply. At birth, the larva of this mosquito swims backward, pressing its siphon against the root of cattail plants. From the end of the siphon it extends first a kind of tweezer that opens a hole in the cattail root. It then inserts its breathing tube into the hole and uses a series of hook like appendages to secure itself firmly in place. The siphori brings the larva air from chambers inside the plant’s roots. The larva will remain suspended there through this stage of life, and the next.
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