INSECTA. 



907 



and the triangular suture, particularly the ante- 

 rior portion, which divides the epicranium 

 from the clypeus posterior (J), is very distinct. 

 At the anterior external angle of this part of 

 the clypeus, as in Coleoptera, are situated the 

 antenna (A), two short and thick porrected 

 organs, covered with a few long hairs, and 

 which, although apparently composed each of 

 two joints, appear to be rigid and motionless. 

 Immediately anterior to the clypeus posterior, 

 and divided from it by a distinct suture, is a 

 short lunated plate (d*), the clypeus anterior. 

 The cornua of this part are extended laterally 

 at the sides of the mouth, and are continuous 

 with a portion of the under surface of the head 

 (f) that bounds the labium. Between the two 

 cornua of the upper surface is extended a strong 

 and somewhat horny membrane (e\ the proper 

 labrum, which is continuous with a similar 

 membrane on the under surface (/), the labium, 

 which thus forms the orifice of the mouth, the 

 parts of which do not appear to have been 

 sufficiently examined in this order. Thus, 

 although the entrance to the mouth is indicated 

 by a distinctly marked labrum and labium, 

 scarcely more developed than in Coleoptera, 

 the habits of the insect require that it should 

 also be furnished with a strong sucking tube. 

 Accordingly we find that within this mem- 

 branous mouth are situated two curved horny 

 plates, a little convex on their external, but 

 concave on their internal surface, and capable 

 of being protruded to some distance. They are 

 directed downwards, and when approximated 

 form a tube analogous to that of Lepidoptera. 

 These parts have been described by Curtis as 

 the maxilla (g), of which they seem to be the 

 proper analogues, so that in the Homaloptera 

 the maxillae form the sheath or outer part of the 

 sucking tube. At the base of these parts, 

 within the cavity of the mouth, are two horny 

 margins fringed with dark hairs, which are 

 probably rudimental maxillary palpi. In the 

 centre of the mouth is situated an elongated 

 slender organ (*), which is folded at an angle 

 like the proboscis of Diptera, but is retractile 

 within the mouth, and extends backwards to 

 the entrance to the oesophagus. It consists of 

 three parts, an inferior one which is strong, 

 horny, and forms a groove or canal, the upper 

 surface of which is covered by another smaller 

 piece, and the two inclose between them a 

 third setiform organ. Upon the precise nature of 

 these parts we do not offer a positive opinion ; 

 the inferior one, which is continuous with the 

 inflected portion of the labium, seems to repre- 

 sent an elongated portion of that organ, and 

 the middle one probably is the lingua, in which 

 case the upper one would answer to a similarly 

 elongated portion of the labrum. 



The under surface of the head is divided by 

 a deep incisure anteriorly, the margins of which 

 are covered with stiff hairs and form the lateral 

 boundary of the mouth. The mention (/), 

 described as such by Curtis, is a strong convex 

 plate, divided also at its anterior part by a con- 

 tinuation of the incisure just noticed. The 

 cornea (c), of an oval convex shape, are situated 

 more on the upper than on the lateral part of 



the head, but the ocelli in this insect are entirely 

 wanting, unless we regard as a large ocellus 

 a convex plate situated in the middle of the 

 most posterior part of the epicranium (6*). 

 In the other genera of this order, as in Hamo- 

 bora, the head is more orbicular and less flat- 

 tened ; the epicranium is broad and distinct, 

 and the suture between this part and the 

 clypeus posterior is strongly marked. In 

 Mt lophagus, the tick or sheep-louse, the maxillae 

 are of considerable length, and the retractile 

 portion of the labium inclosing the lingua is of 

 considerable strength. The ocelli are present, in- 

 serted in little excavations in Hamobora, but ab- 

 sent in Melophagus. In Nycteribida the head 

 offers a most anomalous condition of parts, its 

 form being, as described by Latreille, that of a 

 reversed cone. We have had no opportu- 

 nities of examining for ourselves either the head 

 or parts of the mouth, which, according to 

 Messrs. Curtis* and \Vestwood,f are styliform, 

 and analogous to those of Hippobosca. 



In Aphaniptera the head is compressed 

 from side to side, but we have not yet identified 

 its primary parts. Its chief characteristics are 

 its extreme narrowness, the situation of its 

 antennae, and the peculiarity of its organs of 

 vision, the corneae of the proper eyes being 

 each simple and not compound as in other 

 insects. The mouth is formed upon the same 

 general principles as in the blood-sucking 

 Diptera, being composed of six primary parts 

 adapted for piercing the skin, and occasioning 

 the pain which distinguishes the puncturing of 

 these troublesome insects. 



In Aptera, all of which, like the insects of 

 the two preceding orders, are parasitic upon 

 the bodies of other animals, the mouth in one 

 family, the true Pediculida, is formed for suck- 

 ing, but in the other, the Nirmida, it is dis- 

 tinctly mandibulated, and approaches the usual 

 type of mandibulated insects. 



In Hemiptera the head is often flattened and 

 somewhat triangular, and the mouth is rostri- 

 form as in some of the Diptera, but the sheath 

 of the organ is formed entirely by the labium 

 (fg. 382, k). The corneae are usually very 

 prominent, and are placed at the posterior 

 angles of the head. The epicranium is distinct, 

 but its occipital portion is sunk into a notch in 

 the prothorax. The ocelli are usually two in 

 number, placed on the most posterior part of 

 the epicranium, and are constant throughout 

 the order in the perfect state, but are not deve- 

 loped in the larva or pupa. The division of 

 the head into its primary parts is very distinct 

 in some genera. In Coreus marginatus the 

 epicranial suture is strongly marked along the 

 middle line as far as the space between the 

 corneae, where it joins the triangular suture which 

 passes outwards immediately behind the inser- 

 tion of the antennae, bounding the clypeus 

 posterior. In some specimens, but more par- 

 ticularly in the pupa, a faint longitudinal suture 

 extends forwards over the clypeus as far as the 



British Entomology, pi. 277. 

 t On Nycteribia, in Transactions of the Zoologi- 

 cal Society of London, vol. i. p. 279. 



