88 EXTERNAL ANATOMY OF INSECTS. 



is a large, obtuse, exarticulate terminal lobe. In the Hydrophi- 

 Utes, the maxillary feelers are used as antennae ; they are 

 consequently very long : the helmet is a distinct obtuse lobe. 

 In the Scarabcsites, the feeler-jaws are soft, membranaceous, 

 and hairy ; the helmet is extremely pilose and indistinct. In 

 Lucanus the helmet is remarkable ; it is employed to draw up 

 sap into the mouth, and thus performs the office of a tongue. 

 In the Ceramby cites, CurcuUonites, &c. all the parts are 

 obvious ; their variations are very valuable in generic descrip- 

 tions. In Orthoptera, the parts and appendages of the feeler- 

 jaws are very fully developed. The helmet in this class appears 

 to have reached its maximum ; it is frequently, as in Acridium, 

 three-jointed : in Acheta, the common cricket, it consists of 

 two joints, the basal being the shortei-. In Hemiptera,'^ the 

 feeler-jaws undergo a complete change. Their appendages 

 are obsolete. Their blade is a slender hair, encased in the 

 under lip, already described ; » the pair being united, serrated, 

 and linguiform. 



The MANDiBUL^ or mandihules constitute the fourth section 

 of the head. They are not situated, in tetrapterous hexapods, 

 more in front or further from the prothorax than the feeler- 

 jaws ; but in the apterous octopods they retain their position in 

 front, while the feeler-jaws, with their appendages, take up their 

 station immediately behind. The mandibles are situated above 

 the feeler-jaws and below the upper lip, one on each side the 

 mouth. It is worthy of remark, that the mandibles form a 

 striking exception to the rule which assigns to an insect, longi- 

 tudinally divided down the centre, two equal halves alike in all 

 their parts. The mandibles in those classes, in which they 

 possess the horizontal motion before alluded to, are almost 

 invariably different in the structure of their inner surface. My 

 attention was called to this in the first instance, by finding that 



° In first dissecting the mouth of Hcviiptera, I had concluded, with the early 

 entomologists, that the long lances were never more than three in number. The 

 central filament, which I then supposed to be the tongue, is certainly, in some 

 Cimicites, divisible into two lacinite, which I presume correspond with the maxilltB 

 of other insects. 



° Tous les auteurs out ecrit que le bee des Hemipteres contenait un sucoir 

 forme par trois soies. Le fait n'est pas exact; le sucoir des Hemipteres se 

 compose toujours de quatre soies, bien distinctes, c'est-el-dire, de deux man- 

 dihules et de deux machoires. Ces quatres pieces sont cornees, renflees a la 

 base, comprimees et armees de cils ou de dents tres aigues, lorsque les espdces 

 sont carnassieres. — Savigny. 



