32 EXTERNAL ANATOMY OF INSECTS. 



is a large, obtuse, exarticulate terminal lobe. In the Hi/drop/d- 

 liles, the maxillary feelers are used as antenncc ; they are 

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

 In the ScarabeeiU's, 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 Ccramh y cites, Curciiiionites, &c. all the parts are 

 obvious ; their variations are very valuable in generic descrip- 

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

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

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

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

 two joints, the basal being the shorter. In Hemijdera,'^ the 

 feeler-jaws undergo a complete change. Their appendages 

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

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

 and linguiform. 



The mandibuL/T: or »«««</«/; «/e« constitute the fourth section 

 of tiie 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 

 fi-ont, 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 tlie moutli of Hemiptera, I had concluded, with the early 

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

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

 Cimkiles, divisible into two lacinia, which I presume correspond with the ma-xilta 

 of other insects. 



"> Tous les auteurs out 6crit que le bee des llemiptferes contenait un sucoir 

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

 compose toujours de (juatie soies, bien distinctes, c'cst-il-dire, de deux man- 

 dibules et de deux machoires. Ces quatres piiSces sont cornfies, renflces 4 la 

 base, comprimfies et armies do cils ou de dents trds aiguijs, lorsquc les espiccs 

 sont carnassiircs. — Suvignij. 



