Page:The New International Encyclopædia 1st ed. v. 10.djvu/744

INSECT. 658 INSECT. cdy for the stinps of both hvva and wasps is the iii-tncdinte application of an alkali. Many of tiie poisonous tlics art' treated of under -Mosiji'iTO; Gad-fly; and Hlack-flv. The true l)iij,'s which t:ive a pdisonous bite with a piercing beak, and which may attack man, be- long almost entirely to the family Keduviidic (see Co.NE.NOSE), to which the terms 'pirate- bugs' and "kissing bugs' are a])plicd. The Ka.stern species are Ui)sica:tcs (or hilutius) pcrsoiiulus, .Vilanotestvs piciix's, ami Mcliiiiokstcs ubdomi- nalis; ami the principal Southern and Western forms are liasahus higuttatus and CoiiorhinuD saiiiiuisugus. (See the article CoxEXOSE. ) The bite of these bugs is specifically poisonous, but the great inflammation which so often occurs is doubtless due to the entrance into the cir- "ulatinn of germs of putrefaction, since the bugs are attracted to dead animal matter. The Eastern species i Mitatiolcstc.s jtirijics) is a shin- ing black bug rather more than a half inch in length. The principal Western species {Uithnsus bifiiittatus) is reddish in color with blue black fore wings, each marked with a round reddish spot. This latter species is, according to David- son, the cause of nearl.v all of the supposed cases of 'spider-bites' in the Southwest. EcoLonY. As a class, insects are represented in practically all parts of the world. While flourishing more abundantly in the tropics, they are found in countless numbers in the temperate regions, and are also very numerous in boreal regions. They abound inside the Arctic Circle, and in the short .Arctic sinuncr many species of nearly all orders may be collected. As a rule, as with other classes of animals, the forms occurring in tropical regions are larger in size and more brilliant in color. Many groups are coiitiiiod to the tropics: others have a wide geo- graphic distribution. The value of the class Insecta in the study of the geographic distribu- tion of life is very gieat with certain grovips, while others have comparatively slight faunistic value. Civilization e.crts a direct and destruc- tive influence upon the insect faunas of large regions. Insfcts being largely dependent, directly or indirectly, upon vegetation, the destruction of the wild llora and sylva and the introduction of cultivated crops almost immediatelj- change com- pletely the characteristics of a given insect fauna. The rapid development of methods of transportation, and especially intercommunica- tion between remote regions, hv means of the constantly increasing number and speed of ves- sels, has resulted in the accidental introduction and acclimatization of many hundreds of spe- cies of insects into regions remote from their original homes, many of which succeed in estab- lishing themselves. The facility of acclimatiza- tion varies greatly with difTcrcnt groups, and this facility is dependent upon the degree of sim- plicity of the life of the insect and upon the degree of simplicity of its natural environment. So great has become the danger of the introduc- tion of injurious species from one country' to another during late years, that many nations seek to protect themselves by special quarantine measures. From what has preceded, it is evident that insects, in spite of their small size and their consequent slight strength, have been remarkably successful in the so-called struggle for existence. They have a long geological historj', and the in- sects of Tertiary rocks are in some instances almost generically related to living forms. Kapidity of growth and power of multiplication have been prime factors in this persistence, while the relations which e.ist between circulation and respiration have been almost cipially significant. In many instances the growth from the egg to the individual occupies only a few days, while in .some species a single female will lay several thousands of eggs. The functions of circulation and respiration are so related that nutrition can be carried on very rapidly and very ellicicnlly. By the phenomenon of metamorphosis, growth and development are isolated from one another, allowing growth to go on unchecked and uncom- plicated by development. The social life of insects is very remarkable; organiz.ed societies are formed with many species, especially the Hymenoptcra (bees, wasps, and ants) and the Isoptera (white ants or 'rermiti- difl. In these societies great ninnl>ers of indi- viduals live together and are greatly modified in structure in accordance with the ditfcrent fum- tions which they perform in the coninuuiitv. Sec AxT; Bee; Wa.si'; Termite; and Social tnnccts, below. Reproduction-. Nearly all insects undergo in the course of their lives remarkable changes in form. A f^w forms are ovoviviparous — that is, bring forth living young, but the great majority lay eggs. (See Egg.) With some forms there is a development without metamorphosis, and in these the young insect just hatched from the egg is of the same form as the adult insect. With others there is what is termed an incomplete metamorphosis — that is to say, whore, although the young greatly resemble the adult, there is still a striking change of form during life. 'ith others still there is what has been termed a complete metamorphosis (q.v. (, in which the young just hatched is strikingly different from its subsequent stages. With the bees, butter- flies, flics, beetles, and other insects, the form which hatches from the egg, and which is known as the 'larva,' is a 'grub' or a 'caterpillar.' This, after reaching full growth, passes into another form, which is known as the pupa, and in which in the majority of cases the insect is quiescent, while from this stage there eventually emerges the perfect insect. Larva- grow by molting; the skin is more or less hard and is composed of chitin; a new skin is formed beneath the old skin, which eventually bursts and permits the larva to emerge. The number of molts difTers with the larvip of different groups and ranges from two or three to as many as twelve or more. The phenomenon known as hypermetamorphosis sometimes occurs. With certain of the blister- beetles, for example, the first larva- which are born possess legs, by the aid of which they can cling to a bee and be carried to its nest, where they will live on the food stored by the bee; after a molt they lose their legs and become almost organless, floating about in the honey. Later still, another form of larva is fouml. See Meta- jii)Ki*iio.sis (in Animals); Larva; Pupa. SoctAL Tn.sect.s. a great many insects lead solitary lives. Others, either as larv.T or as adults, are gregarious, and in gregarious feeding and gregarious life we have the beginning of social communities. Many lepidopferous larvie, or eaterpillnrs, feed together in great masses, like the army worm (q.v.) of the United States, and