804 IN SECT A. 



and which Latreille calls a spurious proboscis ; and in regard to this organ 

 Lamarck considers the Hymenoptera as intermediate between the gnawer; 

 and suckers. Among the insects which feed on fluids, or which extract their 

 food by suction, the organs of manducation appear under two modifications. 

 In the first, the mandibles and jaws are replaced by minute laminae, in th< 

 form of seta?, composing by their union, a kind of sucker (haustellum) which 

 is received into a sheath, the substitute for a lip, either cylindrical, conical, 

 or jointed, termed the rostrum or beak in the Hemiptera, or membranous 

 and fleshy, terminated by two lips, termed the trunk or proboscis, in the 

 Diptera. The labium is triangular or conical, and covers the base of the 

 sucker. In the second modification, the mandibles are excessively small, 

 and in the form of a tubercle, more or less triangular, furnished with cilia 

 on the internal margin ; the lip is only distinguished by the presence of 

 palpi; the jaws acquire an extraordinary length, and unite to form a probos- 

 cis or tongue, {lingua,) rolled up in a spiral form. Interiorly, this tongue i? 

 provided with three canals, of which the intermediate is the conduit of the 

 nutritive juices; and at the base of the filaments is a minute palpus. The 

 mouth of the Lepidoptera is an instance of this construction. 



The trunk or thorax is that part of the body which unites the head to the 

 abdomen, and to which are attached the organs of locomotion. It is form- 

 ed of three segments, each with a pair of feet ; but in the winged insects 

 tho upper sides of the last two segments also form points of attachment 

 for the wings. The term thorax has been given to the upper surface of the 

 trunk, and that of breast, to the opposite face below. The middle part of 

 the breast between the feet, is the sternum, and the portion between the at- 

 tich'.nent of the wings, generally triangular, and sometimes very large, i* 

 named the shield, or scutcllum. The anterior segment of the thorax, hi a 

 great many winded insects, is much larger lhan the other segments, and 

 separated from the second, by a very marked articulation ; in others it is 

 extremely short, and has the appearance of a collar, while the two follow- 

 ing segments, of greater size, are internally united, and form a rounded mass, 

 distinct from the abdomen. In both these cases, the large naked portion 

 receives the name of thorax. 



The insects of the first three orders have but one species of locomotive 

 organs, and only proper for walking ; others have, also, wings to the number 

 of four; and the posterior extremity of the thorax is furnished, in those 

 which have only two wings, with two appendages, one on each side, termed 

 : oisers or balancers, [halteres,) and often other appendages in the form of 

 spoonlike scales, (squamulte,) or winglets. 



The wings {ala) are membranous, elastic, gererally transparent, and 

 attached to the upper sides of the thorax. The ribs or nerves, more 

 or less numerous, which run through them, form sometimes a net-work, 

 sometimes anastomosing veins. In wasps and bees, these wings, four 

 m number, are naked and transparent; in butterflies, they are cover- 

 ed with minute scales, resembling fine powder, and embellished with 



