PAP.TS OF INSECTS. 31 



the Hymenoplera and Lepidupiera a large plane of one or more joints in- 

 tervenes between tlie true thorax and the scutel; and it is to this last- 

 inentioncd dorsal space that the term thorax is assigned. Hence it ia 

 evident that the language of Entomology in tliis point is not altogether 

 consistent; because what we denominate the collar in Hymcnoptcra, 

 is the thorax in Cokoptcru ; and in Colcoptcra we find nothing analo- 

 gous to the thorax of the other order, except the collar. 



The thorax in those insects which have that part consisting of a 

 single piece, or the first segment in such as are of a compound nature, 

 has the first pair of legs arising from the lower surface, and it is in 

 this part that the muscles which move the head as well as this pair of 

 legs are said to be contained. The thorax in difterent kinds of insects 

 varies considerably in form, and affords very excellent generic and spe- 

 cific distinctions. Some are armed with spines, others denticulated, 

 inarginated, &c. 



Pectus, the Breast, is the third segment of the body, or that to which 

 the four posterior feet are attached, and which is longitudinally di- 

 vided at tlie anterior part of the sternum. The wings in lepidojiterous 

 and most other insects have their origin or base in the superior part 

 of the breast. The wings and elytra in the Colcoptcra and Hcmiptcra 

 deviate a little from this, as they are placed more iiinnediately on the 

 back tlian in a lateral position; the breast contains tlic muscles that 

 move the wings and give action to the four posterior legs. This part 

 is capable of being compressed and dilated, the alternate motion of 

 which is very evident in some insects of the butterfly or moth kind 

 when held between the fingers. The power of compression and dila- 

 tation is supposed to iu-ise from the action of some very strong mus- 

 cles, being reddish yellow, and extremely loose. It has been con- 

 jectured that these muscles may assist the motions of the organs of 

 flight. 



Sternum, or Breast-bone. By this term entomologists define that por- 

 tion of the middle part of the breast which is situated between the 

 base of the four posterior legs. This piece terminates in some insects 

 anteriorly in a somewhat acute point; in others it appears rather bi- 

 lobate; and in the far greater number ends obtusely or in an obtuse 

 lobe. There are few insects in which the sternum is remarkable, either 

 from its magnitude or figure. In some of the coleopterous tribes, as 

 in the Jiydrophili and Dytici, this part is most conspicuous. 



ScuTELLtM (Linne),the Scutel or Escutcheon: thelobc-like process ;ji- 

 tuated immediately at the posterior part of the thorax in the scutellate 

 insects. The scutel is not of the same form in all insects, yet its general 

 tendency is towards a sub-triangular figure. In the coleopterous tiibes 

 it approaches nearest to this form; its deviations incline more or less to 

 heart-shaped, with the tip pointing backwards. The same figure pre- 

 vaijs \xi some of the Hemiptcra, In the JVeMropfera, Hymenoptera, and 



