INSECTA. 



897 



are kidney-sliaped, and are spread over a great 

 part of the sides of the head. The ocelli, 

 which are found in most of this order, do not 

 exist in Blatta. They are very distinct 4n the 

 Gryttida and Locust'idtf, and also in the mole- 

 cricket; but it is remarkable, as Mr. Kirby for- 

 merly observed, that they are not met with in 

 the pupa or larva state of these insects. In the 

 pupa of the mole-cricket there are simply two 

 slightly elevated tubercles, in the situation in 

 which the ocelli are afterwards developed. 

 They thus appear to have reference to some 

 particular condition of the perfect insect, al- 

 though the habits of the three states appear to 

 be similar. The antenna are organs of much 

 importance, and are usually of considerable 

 length, except in the carnivorous Mantida, or 

 praying insects, in which they are very short. 

 These insects, which take their living food by 

 sight alone, have the shortness of thei* an- 

 tennae, the supposed organs of hearing, com- 

 pensated for by the immense size of their large 

 globular corneae, situated at the superior angles 

 of the head, so as to enable the insect to see in 

 every direction. But in those which reside in 

 the dark, or which seek their food by the aid of 

 other senses, the antennae are exceedingly long, 

 and formed of an immense number of joints, 

 especially in the Gryllida, Achetida, and 

 Blattida, which are noted for acuteness of 

 hearing. In the interior of the head the lamina 

 squamosa are thick and strong, and are articu- 

 lated, as in Hydrous, with the angles of the epi- 

 cranial suture superiorly, and inferiorly with the 

 temm* poster ioj-es, and the tentorium forms a 

 distinct ring, as in Lucanus. 



In the Neuroptera we recognise the same 

 elementary parts in the head and mouth as in 

 the preceding Orders, but in this they are de- 

 veloped into new forms. The epicranium, so 

 conspicuous in the former, is reduced to its 

 minimum in this Order, owing to the immense 

 development of the organs of vision, which, 

 attaining their greatest extent in (Eshna gran- 

 dis, are expanded over the whole of the upper 

 and lateral surfaces of the head, and are ap- 

 proximated together in the median line, leaving 

 only the epicranial suture between them. A 

 small portion only of the epicranium exists 

 anterior to these great corneae, but in that por- 

 tion, as usual, are situated the ocelli; while 

 the minute antennae, reduced also to their mi- 

 nimum of size in these Libellulidte, the most 

 rapacious and insatiable of all insects, are still 

 situated, as in Coleoptera, at the external angles 

 of the suture. In the dilated anterior portion 

 of the head we distinctly recognize the clypeus 

 posterior and anterior, and below these the 

 transverse cordiform labrum, separated by su- 

 tures, but freely articulated together as in Or- 

 thoptera. At the lower concave margin of the 

 clypeus anterior in CEshna grandis is a short 

 triangular plate intervening between the clypeus 

 and labrum, and articulating with both like a 

 distinct segment; it is probably only part of 

 the labrum. On the under surface of the head 

 the guUi and sub-mentum are indistinct, and 

 merged as it were in the construction of three 



VOL. n. 



immensely dilated- doubly articulated plates, 

 which cover the whole lateral and under sur- 

 face of the mouth. The anterior portion of 

 the middle plate, which in (Eshna is rounded 

 at its anterior margin, is the true ligula, while 

 the articulation behind it, from which arise the 

 lateral plates, is the analogue of the mentum. 

 The two lateral plates, composed each of two 

 articulations, and in some species also of a 

 third very minute one in the form of a short 

 spine at the apex, we regard, with Brulle,* as 

 the proper labial palpi immensely dilated. The 

 mandibles concealed within the mouth are 

 short, strong, and, in Libellula quadrimaculata, 

 arched. At the apex they are bifid, and armed 

 with two sharp triangular teeth, and at their 

 base with four sharp-pointed ones, excavated, 

 and placed in different directions, adapted for 

 crushing and cutting rather than for mastica- 

 ting the food. Within the head they are arti- 

 culated with portions of the epicranial and ba- 

 silar regions, as in Coleoptera. The maxilla are 

 long and prehensile. The true palpi are en- 

 tirely absent, but the galea exists as an oblong 

 articulated lobe, and the lacinia, which is arti- 

 culated at its base and sharpened along its 

 inner margin, as in the Blattidte, is armed at 

 its apex with four crooked sharp-pointed teeth, 

 while the cardo is long, and articulated with 

 the base of the maxilla at an angle, to allow of 

 extensive motion, as in the maxilla of Orthop- 

 tera. In other families of the Neuroptera, as 

 in the Panorpida, the organs of manducation 

 are small, but the anterior part of the head is 

 elongated into a rostrum, occasioned by the 

 narrowing and extension of the clypei, as we 

 have before noticed in the Curculumtdtt, while 

 in the Pkryganida:, which take no food in their 

 perfect state, the parts of the mouth are almost 

 atrophied. 



In Hymenoptera the mouth assumes an en- 

 tirely new form, but the changes in it are con- 

 fined to the maxillae and labrum, which are 

 soon to become its chief organs. The head, 

 placed vertically on the thorax, is still well de- 

 veloped. The epicranial region is large, and 

 extends very nearly to the insertion of the 

 antenna? on the front. In most species it is 

 densely covered with hairs, and the ocelli (Jig. 

 375, />,) which are constant in this class, are 

 usually arranged in a triangle on its most ver- 

 tical part. The cornea (c) are large and kid- 

 ney-shaped, and cover part of the lateral sur- 

 face of the head, leaving between them a broad 

 front, occupied by the clypei (d) and part of 

 the epicranium. But in the males of the hive- 

 bee, which come abroad only in the brightest 

 sun-light in quest of the female, this space is 

 diminished, and the corneae are expanded over 

 part of the front, and the whole of the epicra- 

 nial region, as in the Libellula; the most ex- 

 tensive vision being required by these insects, 

 to enable them to discover the object of their 

 solicitude, as by the other in the pursuit of its 

 prey. In some of the pollenivorous and pre- 



* Annal. Soc. Entom. de France, torn. ii. p. 



3 N 



