60 



PROF. AGASSIZ'S 



nevertheless, exists. There is a circulation in In- 

 sects which is only more generally overlooked. 

 The heart is a more elongated tube than in Crus- 

 tacea, but it exists in all insects. It exists more 

 developed in their larval condition, which shows 

 that having a large heart in articulated animals, is 

 not characteristic of a higher structure ; and how 

 a great bulk of blood can be concentrated upon 

 one point in Articulata, without assigning them a 

 character of great eminence, is distincly shown, 

 when we consider that in Worms, which undoubt- 

 edly stand below the other two classes, there are 

 as many as six, eight or more hearts, and in which 

 the bulk of the blood is proportionally much great- 

 er than in Crustacea or in Insects ; so that, the im- 

 portance ascribed to the circulation of Crustacea, 

 when this class was placed above Insects, I think 

 vanishes before the consideration of the value of 

 these characteristics, as noticed throughout the 

 metamorphoses of Insects. 



A few words upon the subject of mastication 

 and upon the chewing orders, will further show 

 that Insects have to stand higher than other articu- 

 lated animals. The chewing apparatus in Insects 

 is a very complicated apparatus, so complicated 

 that it is scarcely possible to give a correct idea of 

 the arrangement of these parts, unless a person 

 has become familiar with the objects themselves. 



I must, however, attempt to convey some idea 

 of this apparatus. On the two sides of the head 

 in those insects which are generally considered the 

 highest, there are two large moveable pieces, mov- 

 ing from right to left on the right side, and from 

 left to right on the left side, in opposite directions 

 horizontally. Ttuese parts are called mandibles. 

 Below these, is another pair of similar organs, 

 moving also horizontally, which are often ser- 

 rated, and to which are frequently added articu- 

 lated appendages: these are called the maxillae. 

 These constitute two pairs of strong forcep-like 

 jaws, very different, it seems, from any part in the 

 whole insect. 



In the diagram here, Jaws of Insects (Plate XVI. 

 ngs. A, B) your see the whole apparatus, first from 

 a Beetle and a Grasshopper, (fig. C). Seen from 

 above (fig. A) there is u kind of lip in sight, cov- 

 ering the mandibles, and below, are the maxillse ; 

 and below (tig. B) there is another kind of lip,keep- 

 ing these in their respective positions. To the 

 lower lip are also frequently appended articulated 

 tentacles the palpi. Fig. C represents the maxillae 

 of a Grasshopper seen in profile. 



Now, each of these parts being taken asunder, 

 we will have a strong mandible above ; and some- 

 what below and inward, the maxillae ; and farther 

 below, we have the lower lip. So that, between two 

 horizontal continuous plates, called lips, there are 

 moving forceps, the upper, called mandibles, and 

 the lower maxillae. Then we have maxillary pal- 

 pi. And to the lower lip there is another pair of 

 palpi attached the labial palpi. 



This is the structure of the jaws in all chewing 



[PLATE XVI JAWS OF INSECTS.] 



insects. The Caterpillars have also such maxillae 

 as the perfect chewing insects, though not so com- 

 plicated, to be sure, as in the most perfect Beetles, 

 but nevertheless constructed in the same way.with 

 a horny, powerful jaw, by which they chew the 

 large quantity of food which they devour. Now 

 this condition is changed in the Caterpillar during 

 the pupa condition, when we have no longer such 

 enlarged jaws; but a long sucker [Plate XVI fig. D] 

 consisting, however, of the same parts as in the 

 chewing insects, only those parts which were mov- 

 ing horizontally have become elongated, and with 

 their margin have united, and instead of now mov- 

 ing in that way, remain closed together, and form, 

 a tube, a real sucker, through which, by the assist- 

 ance of the tongue, they actually pump liquid food 

 into their stomachs. (The Professor here repre- 

 sented, by means of his fingers, the jaws of the 

 chewing insect, and the manner in which, by uni- 

 ting, they can be transformed into a sucker.) 



Let the tube now be contractile and retractile,be- 

 tween the upper and lower lip, and you have pow- 

 erful jaws transformed into a narrow tube. It is 

 a transformation which takes place with the other 

 successive and progressive changes, so that we are 

 entitled to consider such changes as also a pro- 

 gress, if I am not mistaken ; and to consider the 

 condition of the insect in which he chews food, as 

 the lower one, as it is the condition of the Larva; 

 and the condition in which he sucks, to be the 

 higher condition of the insect. And therefore, in 

 principles derived from the study of Insects, and 

 not from the study of other animals, judging of 

 Insects by notions gained from that class, we shall 

 consider those which suck their food, in which the 

 jaws are elongated, those which pass through vari- 

 ous metamorphoses, higher than those in which 

 the jaws are placed horizontally sharp cutting 

 jaws,which devour large quantities of food. But this 



