Fig. 115.—Under side of head and front of prothorax of Hemimerus. a, base of antenna; b, articulation of antenna; c, labrum; d, mandible; e, condyle of mandible; f, articular membrane of mandible; g, stipes of maxilla; h, exterior lobe; i, palpus of maxilla; k, submentum; l, mentum; m, terminal lobe of labium; n, labial palp; o, plate between submentum and sternum; p, prosternum; q, cervical sclerites. (After Hansen.)

In describing the labium of Mandibulata, p. [97], we alluded to the genus Hemimerus as reputed to possess a most peculiar mouth. When our remarks were made little was known about this Insect; but a very valuable paper[[145]] by Dr. H. J. Hansen on it has since appeared, correcting some errors and supplying us with information on numerous points. M. de Saussure described the Insect as possessing two lower lips, each bearing articulated palpi, and he therefore proposed to treat Hemimerus as the representative of a distinct Order of Insects, to be called Diploglossata. It now appears that the talented Swiss entomologist was in this case deceived by a bad preparation, and that the mouth shows but little departure from the ordinary mandibulate type. There is a large inflexed labrum; the mandibles are concealed by the maxillae, but are large, compressed, and on their inner edge toothed. The maxillae are well developed, are surmounted by two lobes and bear five-jointed palpi. The ligula appears to be broad and short, and formed of two parts longitudinally divided; the short palpi consist of three segments. The mentum is very large. The lingua is present in the form of a free pubescent lobe with a smaller lobe on each side. The structure of the pleura is not fully understood; that of the abdomen seems to be very like the earwigs, with a similar difference in the sexes. The cerci are something like those of Gryllidae, being long, flexible, and unsegmented. The legs have rather small coxae, and three-jointed tarsi, two of which are densely studded with fine hairs beneath, as in Coleoptera. It is difficult to detect the stigmata, but Dr. Hansen believes there are ten pairs.

Fig. 116.—Foetus of Hemimerus. (After Hansen.) a, Antenna; b, organ from the neck; c, cerci; d, membrane (? cast skins).

Fig. 117.—Hemimerus talpoides. Africa. (After de Saussure.) A, Upper; B, under surface.

The species described by Dr. Hansen as H. talpoides is probably distinct from that of Walker, though both come from equatorial West Africa. Dr. Hansen's species, which may be called H. hanseni, has been found living on the body of a large rat, Cricetomys gambianus; the Insect occurred on a few specimens only of the mammal, but when found was present in considerable numbers; it runs with rapidity among the hairs and apparently also springs. The nature of its food is by no means clear. Not the least remarkable fact in connexion with this peculiar Insect is its gestation. The young are borne inside the mother, apparently about six at a time, the larger one being of course the nearest to the orifice. Dr. Hansen thinks the young specimens are connected with the walls of the maternal passages by means of a process from the neck of each. But the details of this and other points are insufficiently ascertained; it is, indeed, difficult to understand how, with a process of the kind of which a fragment is shown in Fig. 116, b, the Insect could fix itself after a detachment for change of position. The young is said to be very like the adult, but with a simpler structure of the antennae and abdomen. On the whole, it appears probable that Hemimerus is, as stated by Dr. Hansen, a special family of Orthoptera allied to Forficulidae; further information both as to structure and development are, however, required, as the material at the disposition of the Swedish entomologist was very small.

CHAPTER IX

ORTHOPTERA CONTINUED—BLATTIDAE, COCKROACHES