EXTERNAL ANATOMY OF INSECTS. 415 



gies that hold in this respect between the different tribes. 

 Thus the Coleoptera are analogous to the Heteropterous 

 Hemijpterct; the Orthoptera, with the exception of the 

 Mantidce, to the Homopterous Hemiptera ; the Mantidce 

 to the Libellulina ,- the Lepidoptera to the Trichoptera ,- 

 the Hymenoptera to the Diptera, with a slight variation, 

 and probably others might be traced. 



viii. A word or two upon the motions of which the 

 head of insects is capable. M. Cuvier, in the extracts 

 lately laid before you, speaks of different powers of move- 

 ment as the result of different configurations of the parts 

 of the head. This probably is correct with regard to 

 many cases ; but a great deal will depend upon the power 

 the insect has of protruding its head and disengaging 

 its base from the restriction of the prothorax ; for where, 

 like the Harpali, Staphylini, &c. it is able to do this, it 

 can probably move its head in every direction. It is 

 only where the ligaments are less elastic, or allow of lit- 

 tle tension, that its movements are confined; and few 

 living insects have been sufficiently examined to ascer- 

 tain how far this takes place. In those cases belonging 

 to the third section of articulations, in which the head 

 moves upon the thorax as upon a pivot, as is the case 

 with Hymenoptera and Diptera, the movement is nearly 

 versatile. I have seen a fly turn its head completely 

 round, so that the mouth became supine and the vertex 

 prone; and from the form and fixing of the head, it 

 should seem that those of the Mantidce were endued 

 with the same faculty. 



ix. The parts and appendages of the head are now in 



