Page:Popular Science Monthly Volume 70.djvu/60

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56 POPULAR SCIENCE MONTHLY

hemispheres; and about 4,000 species of their nearest relatives, the locusts, or Acrididse, to which group the notorious migratory locusts also belong. It is estimated that there are about 2,500 kinds of spec- ters, or walking-sticks (Phasmidse), which inhabit tropical regions chiefly and are noted for their close resemblance to twigs and leaves. Much smaller is the number of those creatures called earwigs, although they are neither worms nor crawl into the ears; scientifically they are termed Dermaptera, and comprise about 500 species. Less noteworthy are the 200 forms of small thrips, or Physopoda. The stately, but harmless, praying-crickets, or Mantidse, are represented throughout the world by only 800 different species. On the other hand, about 1,200 kinds of cockroaches, or Blattidae, are known, and this family unfor- tunately includes the small Croton-bug and its larger black cousins. In warm countries, with these troublesome creatures are associated about 400 different species of white ants. The very small insects called body-lice, book-lice or wood-lice, which belong to the Corrodentia or Copeognatha, are represented in almost equal numbers. Mallophaga (bird-lice, which should not be confounded with bird-ticks) already number 1,300 species, for nearly every kind of bird has its special parasite. On the other hand, luckily, only 50 species of true blood- sucking lice have become known, a relatively high percentage of which afflicts mankind. One hundred and sixty thousand species is certainly not too large a figure to include the hosts of beetles, or Coleoptera, which people every corner of the globe, and may be obtained in the region of perpetual ice as well as in salt marshes. We are acquainted with but 52,000 species of Hymenoptera, or membrane-winged insects, among which are the many ' wild ' relatives of the honeybee, the colo- nies of ants, the true wasps, digger-wasps, ichneumon-flies, gall-flies, saw-flies, golden-wasps and wood-wasps. Of dragon-flies, or libellids (Odonata), there may be about 2,300 different kinds at present de- scribed, while 300 species of May-flies (Plecoptera) and stone-flies (Perlidae) are recognized. True JSTeuroptera (netted-winged insects), which also include the ant-lions and lace-winged flies, number 1,400 species; Panorpidse, or scorpion-flies, about 100, and caddice-flies, or Phryganeidse, 1,200. After the beetles, the forms most abundant in species are the butterflies, or Lepidoptera; of these science has dis- closed the existence of about 55,000 species up to the present time. Next come the much less noted two-winged insects, or Diptera, of which two main groups, Orthorrhapha (midges, gnats, horse-flies, etc.) and Cyclorrhapha (true flies), with 14,000 and 30,000 species, re- spectively, share in the sum total of insect forces. The number of fleas, or Suctoria, is small in comparison, only 100 species as yet being known, one of which lives on the blood of mankind. Further, if the 30,000 kinds of bugs, cicadas and plant-lice included in the Hemiptera,

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