908 



INSECTA. 



Fig. 382. 



Head of Pentatoma rufipes (Savigny). 



most anterior portion of the front of the head, 

 where it joins with a second triangular suture 

 which passes outwards on each side anterior to 

 the insertion of the antennae, and thus divides 

 the clypeus anterior from the posterior. The 

 proper triangular suture between the epicranium 

 and clypeus passes backwards from behind the 

 insertion of the antennae along the sides of the 

 head as far as the margin of the cornea, thus 

 clearly indicating the extent of the epicranial 

 region, as in Coleoptera. The clypeus anterior 

 is distinctly marked at the front of the head (d) 

 as a narrow elongated plate, a little widened at 

 its lower portion, where it is articulated with the 

 labrum (e\ which is narrow, lengthened, and 

 ends in a point, and covers the front of the 

 proboscis (&), which is formed of four joints 

 or articulations, and is believed by Savigny to 

 represent the true labrum. This part, which, 

 in a state of rest, is concealed beneath the 

 under surface of the head and prothorax, forms 

 a cylindrical tube throughout nearly its whole 

 length, from its apex to its base, where it is 

 covered by the labrum. It incloses four dis- 

 tinct setae, which have been shewn by Savigny 

 to be the proper mandibles and maxillae. We 

 are satisfied of the correctness of this opinion 

 from our own examination of these parts, the 

 insertion of the muscles belonging to them 

 being in the basilar portion of the head, as in 

 all the preceding orders. But it is in Reduvius 

 that the parts of the head are most distinctly 

 marked. The occipital portion is so much 

 elongated backwards as to form a very distinct 

 neck, narrower considerably than the other 

 parts of the head, and the corneas are large and 

 protuberant and stand out from its broadest 

 part, while the ocelli, two in number, are also 

 exceedingly large and are placed on short 

 pedicles almost on the constricted neck-like 

 part of the epicranium, far behind the cornea, 

 and with their axis directed posteriorly. Be- 

 tween this portion of the head and that which 

 contains the true corneas is a deep transverse 

 impression, which seems to indicate that the 

 cornese and ocelli are derived from distinct seg- 

 ments. But one of the most marked charac- 

 teristics of the epicranium in this insect is the 

 existence of a triangular elevation or ridge, 



which commences in the usual situation of the 

 suture in the middle line between the corneas, 

 and extending outwards marks the course of 

 the antennae. The posterior margin of this 

 ridge is in the usual direction of the triangular 

 suture, posterior to the insertion of the antennae. 

 Anterior to this is a lozenge-shaped plate, the 

 clypeus posterior, which is elevated along its 

 middle line, and which is continuous with a 

 similar elevation on the clypeus anterior. The 

 labrum is short, and terminates in a triangular 

 process, that covers the base of the proboscis 

 as in the preceding species. We have thus 

 five clearly indicated segments in the head of a 

 perfect insect, the occipito-basilar segment 

 bearing the ocelli, the proper epicranial with 

 the corneas and antennae, the two clypeal, and 

 the labial. The proboscis consists, as in 

 Coreus, of four distinct articulations, which 

 form the labium, and correspond to the seg- 

 ments of the upper surface of the head, but 

 which are extended forwards and form a sheath 

 for the setiform mandibles and maxillae. In 

 the Hydrometrida, which connect the terrestrial 

 with the aquatic Hemiptera, the head is elon- 

 gated forwards, and the cornese, which are large 

 and kidney-shaped, are very protuberant. In 

 Gerris paludum the epicranial region is short, 

 but the suture is still very distinct. It divides 

 as usual at a point opposite to the middle of 

 the corneae, and passes outwards to their ante- 

 rior margin. The clypeus posterior is broad 

 and lengthened, and seems to have become 

 united with the anterior, and the antennae are 

 moved forwards to the base of the proboscis. 

 The Nepida have a form of head similar to 

 that of the Hydrometridse, but the epicranial 

 region (Jig. 383, d) is of greater extent. In 



Fig. 383. 



Upper and under surface of the head of Nepa cinerea 

 (Savigny.) 



a, occiput ; b, epicranium ; c, cornea ; d, cly- 

 peus posterior ; e, labrum ;/, mandibles ; g, maxil- 

 lae j *, labium ; *, lingua. 



the figure which we have copied from Savigny 

 the parts of the head are not distinguished, 

 but they are distinct in the insect. The epicra- 

 nial suture, the proper guide to a correct deter- 

 mination of the primary parts of the head in 

 every species, bounds the corneas anteriorly and 



