ENTOMOLOGY. 



51 



and observations show that no species is without 

 them, or, at least, something similar to them ; and, 

 in many insects, they are larger in proportion to 

 their bodies than in other animals. In most of them 

 they lie at or near the surface of the body, and send 

 out lateral pores or trachea. The respiration of 

 insects has attracted the attention of many natural- 

 ists ; and it is found that insects do not breathe 

 through the mouth or nostrils ; that there are a 

 number of vessels, for the reception of air, placed 

 along on each side of the body, commonly called 

 spiracula, which are subdivided into a number of 

 smaller vessels, or branchiae; that the vessels, or 

 tracheae, which proceed from the pores on the sides, 

 are not composed of a simple membrane, but are 

 tubes formed of circular rugae ; that the spiracula 

 are distinguishable, and are covered with a small 

 scaly plate, with an opening in the middle like a but- 

 ton-hole, which is furnished with membranes, or 

 threads, to prevent the admission of extraneous 

 bodies. 



Insects are the only animals without vertebrae, in 

 which the sexes are distinguished. Copulation is 

 performed in them by the introduction of the parts of 

 generation of the male into those of the female. All 

 insects are either male or female, except in a few of 

 the genera of the order hymenoptera.such as the bee, 

 ant, &c., where individuals are to be found, which 

 are neither male nor female, and, on that account, 

 called neuters. Among the bees, the neuters form 

 the far greater part of the community, and perform 

 the office of labourers. Among the ants, the neuters 

 are very numerous, and constitute the only active 

 members of the society. It has been alleged, that 

 these neuters are nothing but females, whose parts 

 have not been developed for want of proper nourish- 

 ment. Oliver, however, after strict examination, is 

 disposed to think them really different, though he 

 does not adduce facts sufficient to establish his 

 opinion. The parts which distinguish the male from 

 the female may be divided into two classes, viz., I. 

 those which are not directly connected with genera- 

 tion; 2. those which are absolutely necessary for 

 the purposes of generation. The circumstances 

 which have no direct communication with generation, 

 which serve to point out the distinction between the 

 sexes, are the difference of size observable in the 

 male and female ; the brightness of the colour in each; 

 the form and number of articulations of the antennas ; 

 the size and form of their wings ; the presence or ab- 

 sence of a sting. The male is always smaller than 

 the female ; the female ant is nearly six times larger 

 than the male : the female cochineal is from 12 to 

 15 times the size of the male ; the female termes is 

 200 or 300 times the size of the male ; the colours of 

 the male are commonly much more brilliant than 

 those of the female ; this is particularly the case in 

 lepidopterous insects ; in some insects, the colour of 

 the male is totally different from that of the female : 

 the antennae of the male are commonly of a different 

 form, and larger than those of the female : frequently 

 the males are furnished with wings, while the females 

 have none ; the lampyris, coccus, and blatta and 

 several moths, afford an example of this : the female 

 bee is furnished with a sting, while the male is desti- 

 tute of one : the males of some insects are furnished 

 with sharp, prominent points, resembling horns, 

 situated either on the head or breast, which are either 

 not perceptible, or very faintly marked in the 

 female. The parts essential to generation afford the 

 best distinguishing mark ; in most insects, they are 

 situated near the extremity of the rectum ; by pressing 

 the abdomen near to the anus, they may frequently 

 be made to protrude ; but the parts of generation are 

 not always situated near the anus; in the spiders, 



they are situated in the feelers ; in the libellula, the 

 male organ is situated in the breast, while that of the 

 female is placed at the anus. 



The eggs of insects are of two sorts; the first 

 membranaceous, like the eggs of the tortoise and the 

 other reptiles ; the other covered with a shell, like 

 those of the birds. Their figure varies exceedingly ; 

 some are round, some elliptical, some lenticular, 

 some cylindrical, some pyramidal, some flat, some 

 square ; but the round and oval are the most com- 

 mon. The eggs of insects seldom increase in size, 

 from the time they have been deposited by the 

 parent till they are hatched : those of the tenthredo, 

 however, and of some others, are observed to increase 

 in bulk. At first, there is nothing to be perceived 

 in the eggs of insects but a watery fluid ; after some 

 little time, an obscure point is observable in the 

 centre, which, according to Swammerdam, is not 

 the insect itself, but only its head, which first acquires 

 consistence, and colour ; and the same author 

 alleges, that insects do not increase in bulk in the 

 egg, but that their parts only acquire shape and 

 consistence. Under the shell of the egg, there is a 

 thin and very delicate pellicle, in which the insect 

 is enveloped, which may be compared to the chorion 

 and amnios, which surround the foetus in quadrupeds. 

 The little insect remains in the egg till the fluids are 

 dissipated, and till its limbs have acquired strength 

 to break the egg and make its escape ; the different 

 species of insects remain enclosed in the egg for 

 very different periods ; some continue enclosed only 

 a few days, others remain for several months. The 

 eggs of many insects remain without being hatched 

 during the whole winter, and the young insects do 

 not come forth from them till the season at which 

 the leaves of the vegetables, on which they feed, 

 begin to expand. When the insects are ready to 

 break their prison, they commonly attempt to pierce 

 the shell with their teeth, and form a circular hole, 

 through which they put forth first one leg, and then 

 another, till they extricate themselves entirely. 



Insects afford nourishment to a great number of 

 the superior animals; many of the fishes, reptiles, 

 and birds> draw the principal part of their susten- 

 ance from that source. The immense swarms of 

 different species of crab, which abound in every sea, 

 directly or indirectly form the principal part of the 

 food of the cod, haddock, herring, and a great 

 variety of fishes. The snake, lizard, frog, and many 

 other reptiles, feed both on land and aquatic insects. 

 Gallinaceous fowls, and many of the small birds, &c., 

 feed on insects. Swallows, indeed, feed entirely on 

 winged insects. They afford food, likewise, to 

 many of the mammalia, viz., to many species of the 

 bat, to the ant-eater, &c., and even to man himself. 

 Many species of crab, viz., lobster, common crab, 

 shrimp, prawn, land-crab, &c., are reckoned delica- 

 cies. The larvae of some coleopterous insects and 

 locusts form part of the food of man. Insects, like- 

 wise, by consuming decayed animal and vegetable 

 matter, which, if left to undergo the putrefactive pro- 

 cess on the surface of the ground, might taint the 

 atmosphere with pestilential vapours, preserve the 

 air pure for the respiration of man and other ani- 

 mals. On the other hand, the injuries which they 

 inflict upon us are extensive and complicated ; and 

 the remedies which we attempt, are often aggrava- 

 tions of the evil, because they are directed by an 

 ignorance of the economy of nature. 



The little knowledge which we have of the modes 

 by which insects may be impeded in their destruc- 

 tion of much that is valuable to us, has probably 

 proceeded from our contempt of their individual 

 insignificance. The security of property has ceased 

 to be endangered by quadrupeds of prey, and yet our 

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