INSECTS. 



which they extract from flowers : indeed, 

 the construction of their mouths pre- 

 .vents them from taking any other than 

 fluid food. 



We shall now refer to the functions of 

 insects : beginning with respiration, which 

 is the act of inhaling and exhaling the air 

 into and out of the lungs. Quadrupeds, 

 birds, and most of the amphibia, breathe 

 t hrough the mouth and nostrils. The air, 

 when received into the lungs, is mixed 

 with the blood, and imparts to it some- 

 thing necessary, and carries off something 

 noxious. Some authors have asserted, 

 that insects have no lungs ; but later ex- 

 periments and observations show, that no 

 species wants them, or, at least, some- 

 thing similar to them ; and in many insects 

 they are larger in proportion to their bo- 

 dies than in other animals. In most of 

 them they lie at or near to the surface of 

 . the body, and send out lateral pores or 

 tracheae. 



The respiration of insects has attracted 

 the attention of many naturalists, 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, 

 which are commonly called spiracula, 

 which are subdivided into a number of 

 smaller vessels, or bronchiae ; 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 spira- 

 cula are distinguishable, and are covered 

 with a small scaly plate, with an opening 

 in the middle like a button-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 distin- 

 guished. Copulation is performed in them 

 by the introduction of the parts ofgener- 

 tion of the male into those of the female. 

 All insects are either male or female, ex- 

 cept 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 nou- 

 rishment. Oliver, however, after strict 

 examination, is disposed to think them 



really different, though he does not ad- 

 duce facts sufficient to establish his opi- 

 nion. The parts which distinguish the 

 male from the female may be divided into 

 two classes, viz. 1. Those which are not 

 directly connected with generation. 2. 

 Those which are absolutely necessary for 

 the purposes of generation. The circum- 

 stances which have no direct communica- 

 tion 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 antennae ; the size and 

 form of their wings ; the presence or ab- 

 sence of a sting ; the male is always small- 

 er than the female; the female ant is 

 nearly six times larger than the male; 

 the female cochineal is from twelve to 

 fifteen times the size of the male; the 

 female termes is two hundred or three 

 hundred 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 lepidopter- 

 ous insects ; in some insects, the colour 

 of the male is totally different from that of 

 the female; the antennze 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 molhs, afford an 

 example of this ; the female bee is fur- 

 nished with a sting, while the male is des- 

 titute 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 per- 

 ceptible, 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 fre- 

 quently be made to protrude; but the 

 parts of generation are not always situat- 

 ed 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 exceed- 

 ingly ; some are round, some elliptical, 

 some lenticular, some cylindrical, some 

 pyramidal, some flat, some square, but 

 the round and oval are the most common. 

 The eggs of insects seldom increase in 



