896 



INSECTA. 



with the mandibles in mastication," and that 

 "this is a departure from a general law of 

 nature, and its occurrence is well worth re- 

 marking; as the motion of the shield might in- 

 duce an observer to suppose it the lip, which 

 would consequently become a new and super- 

 numerary elementary part." Thus, then, the 

 motion of this part in Orthoptera is considered 

 as an anomalous condition, but the same thing 

 occurs in Coleoptera. In Dyticidf, the cly- 

 peus is freely moveable, as well as the labrum, 

 and probably this mobility has reference to the 

 rapacious habits of the insects. 



The inferior surface of the head in Orthoptera 

 varies a little from the type of the Coleoptera, 

 although it is formed, as in that order, of four 

 distinct parts. The gula, or basilar region (m), 

 which includes part of the occipital foramen, is 

 a broad transverse plate, rounded at its lateral, 

 and concave at its anterior and posterior mar- 

 gins. In the mole-cricket, as in most of the 

 beetles, the true gula is well developed be- 

 tween the occipital foramen and sub-men- 

 tum, and in that insect is of a trian- 

 gular shape, with its apex directed backwards. 



Fig. 374. 



Under surface of mouth of Blatta. Figures as 

 before. 



But in the Blattida: (fig. 374, m), the sub-men- 

 tum and gula appear to have been closely 

 united, without trace of their former distinc- 

 tion, and the mentum (I) is short, transverse, 

 and articulated with the palpiger and ligula 

 (i). From the complexity of parts into 

 which the ligula is divided, we consider it 

 better, as before remarked, to omit any parti- 

 cular description of the palpiger, which, Mr. 

 Newman states, is situated between the proper 

 ligula and mentum. In Blatta the ligula is 

 divided into six distinct parts. To two of these 

 (/) are attached the labial palpi, and they ap- 

 pear to be the palpiger as described by New- 

 man. From the upper anterior margin of 

 these, nearest the median line, arise two short 

 lobes, covered partly on their exterior margins 

 by two larger ones, the paraglotte (* *), 

 which become of much importance in the 

 mouth of Hymenoptera. In the mole-cricket 

 the ligula is divided only into four lobes, all of 

 which are exceedingly narrow, and very much 

 resemble palpi. In some of the Locuslida; 

 the labium is simply divided in the median 

 line as in Hydrous. The true ligula or tongue 

 (fig. 374*) in most of the Orthoptera is a 

 soft projecting fleshy body, like the tongue of 



other animals, and is situated above the men- 

 tum and sub-mentum, within the mouth of 

 which it forms the floor and passage to the 

 pharynx. In Blatta it is narrow and elon- 

 gated, and projects as far as the middle of the 

 ligula, and it is even more largely developed in 

 the Locustidtf and Achetida. In the maxillie 

 we recognise the same parts as in Coleoptera, 

 with but little variation of form except in the 

 galea and lacinia. The lacinia (5) is usually 

 elongated, and furnished with a sharp hook 

 bipid at its apex. In Achetida and most of 

 the vegetable feeders it is strong and much 

 bent at its extremity, but in the omnivorous 

 Blattidte it is also sharpened to a cutting edge 

 along its inner margin. It is in this order of 

 insects that the secondary appendage of the 

 maxilla, the galea (6), is most fully developed, 

 and covers the lacinia so completely as to serve 

 the office of a shield or helmet. In the vege- 

 table-feeding Loctutidtf, this part is sometimes 

 three-jointed, as observed by Newman* in 

 Acrydium, but usually it is simply an obtuse 

 double-jointed organ, hollowed on its inner 

 side; but in the Blattida it is expanded at its 

 extremity into a thick oval bulb, or soft 

 cushion, encircled with fine hairs, evidently 

 well adapted for touching or feeling. In all 

 the Orthoptera, but more particularly in the 

 Bliiltidtc, the articulation of the maxilla with 

 the sub-mentum is less compact than in the 

 Coleoptera ; and this appears to be referable to 

 the same circumstance as before noticed with 

 regard to the mobility of the anterior clypeus, 

 the voracious habits of the insect. Thus, to 

 allow of very extensive motion to the parts, the 

 stipes (2) is articulated at an angle with the 

 cardo (1), and a broad muscular structure, at- 

 tached along the inner border of the lacinia, as 

 far as the base of its sharp articulated apex, 

 upon which it acts, is interposed between the 

 maxilla and sub-mentum, and forms part of the 

 inferior boundary of the mouth. The mandibles 

 in this order of insects, as remarked by Marcel 

 de Serres,-)- are more perfectly constructed than 

 in any other. In those which masticate their 

 food, and devour large quantities of vegetable 

 matter, as the Locustidtz, the mandibles are 

 furnished both with cutting and grinding sur- 

 faces. The anterior or apical margin is deve- 

 loped into acute cutting teeth, somewhat like 

 the canine teeth of vertebrata, while the inner 

 and posterior part of the mandible is broad, 

 flattened, and covered with elevated irregular 

 ridges, like the teeth of some Herbivora, and is 

 admirably adapted for grinding or chewing. 

 This complicated structure does not exist in 

 the more carnivorous species, the Blattida, in 

 which the mandibles are arched, and indented 

 with sharp triangular teeth (fig. 373,/,), very 

 closely resembling the cutting teeth of Carni- 

 vore, and are articulated by strong condyles at 

 the side of the head, on a line with the articula- 

 tion of the clypeus anterior, and not so far back 

 as that of the maxilla. The eyes in Orthoptera 

 are usually exceedingly prominent and round, 

 but not large, except in Blatta, in which they 



* P. 32. 



t Amiak-s dus Museums, No. xvi. p. 56. 



