Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/131

Rh MYRIAPODA 119 feeders. In the tropics very large representatives of the Julidae occur, especially species of the genus Spirobolus, which do consider able damage in gardens by devouring leaves. In the Polyzonidas (tig. 7) the mouth parts are formed into a pricking and sucking beak or tube. In the Polydesmida the body is semi-cylindrical in section, with the lateral regions of each tergum broadened out into a pair of horizontal projecting plates. In the Palaeozoic Diplopoda, Euphorberict and its allies, the terga bore each six stout projecting spines, forming rows of spines along the body (fig. 6) ; the sterna en closed one-third of the circuit of the body instead of only an insignificant ventral streak as in the Julidae. In addition to the stigmata there are found on the ven tral aspect of these fossil forms certain paired organs supposed by Scudder, who conjectures that these ancient Diplopoda may have been amphibious in habits, to have given support to gills. In the Glo- mcridie the body is shortened, of twelve or thirteen somites only, and closely simu lates that of the woodlouse in appearance. The males of Spfuerotherittm, a genus of this family, possess a stridulating appara tus at the hinder end of the body Very important from a zoological point of view are the genera Polyxcnus and Pau- ropus, the species of both of which are ex tremely small. Polyxenus (fig. 8) is about one-twelfth of an inch in length, and has fourteen pairs of legs, only the first four FIG. 8. Ventral view of pairs of which are borne on the first four Sf^JlSSLgSS. post-cephalic somites. 1 he body is covered tual length a little over with bundles of hairy scales. In Pa u rop us -^th of an inch, o, position (tig. 9) only nine pairs of legs are present, of generative openings. The antennae are branched at their tips ; the first post-cephalic somite bears a single pair of legs, the second post-cephalic a single FIG. 9.- Enlarged view of Pauropus Hu.deijl. (After Lubbock.) pair of legs, and the remaining somites, except the posterior which bears a single pair, two pairs each. Sir John Lubbock, the dis coverer of this form, which has many aberrant features besides those described above, referred it to a separate order of Myriapods, Pauropoda, Order Chilopoda. Myriapoda mostly of dorso-ventrally compressed form, with long multi-articulate antennae ; with the second pair of post - cephalic appendages applied to the mouth as poison-claws ; only one sternum and one pair of legs to each somite ; stigmata lateral (in Scutigera dorsal) ; trachea! organs ramified, not tuft - shaped, often anastomosing ; generative openings posterior ; larvae born with more than three pairs of functionally active legs. In Scolopendra (fig. 10) the body is band-like and flattened dorso- ventrally. The terga and sterna are nearly flat broad plates of chitinous material, connected laterally by more flexible softer skin, in which in each somite lies on either side a single stigma. The corresponding large ramified tracheal trunks, which are provided internally with well-developed spiral filaments, are connected on each side by lateral longitudinal anastomosing tubes. The antenna? are many-jointed, long, and tapering ; the head is followed by a second compound somite formed of four embryonic somites fused, termed the &quot;basilar somite,&quot; which is covered by a single enlarged shield-like tergum. The legs are borne at the lateral margin of the ventral surface, their bases being wide apart ; one pair is present to every post-basilar somite. The mandibles are provided with sharp cutting teeth ; the maxillae are fused together in the middle line as in Diplopods. They do not form a plate, but in the centre a small bilobed process only, and bear a pair of soft palps laterally (fig. 11). The basilar somite bears as the first pair of post-cephalic appendages a pair of palp-like legs turned forwards in front of the mouth, and as the second a pair of large powerful limbs, the poison-claws, provided with a pair of curved claws perforated at their extremities by the ducts of poison-glands embedded in the claws and their penultimate joints. The basilar somite may bear posteriorly in addition a pair of walking legs, but this pair is frequently aborted in the adult animal. The last pair of legs at the hinder extremity of the body is elongated and directed backwards in the line of the body posteriorly. The generative ducts open posteriorly beneath the anus. The Chilopoda are all carnivorous, catching their prey and killing it by means of the poison- claws. Eucorybas crotalus of S. Africa makes with its hind legs a rattling noise like that of the rattlesnake. Arthronomatus longicornis of Europe is phosphorescent in the dark. The Fig. 10. Fig. 11. FIG. 10. Scolopendra inorsitans (after Buffon). n, cephalic tergite ; 5, basilar tergite ; c, first post-cephalic appendage (=third post-oral) ; d, third post- cephalic ; e, antenna; /, second post-cephalic ( = poison-claws) ; g, last pair of appendages enlarged and directed backwards. FIG. 11. Mouth pairs of Scolopendra inorsitans (after Bnffon). 1, the poison- claws or fourth post-oral appendages ; s, median cutting processes formed by the anterior edge of the basilar sterna ; 2, one of the mandibles with its cutting edge to the left ; 3, the maxilhc and third post-oral appendages a ; e, palp-like maxillse ; 6, small process formed by their fused bases ; 4, ventral view of head with jaws removed ; as, eyes ; e, labrum. Gcophilidee, which are without eyes, have very long worm -like bodies, composed of very numerous segments. They live gregari ously in moist earth. In Lithobius, the commonest British Cen tipede, the somites are unequal in size, there being nine larger and six smaller terga and fifteen legs composed each of six joints and a claw. The genus Scutigera and its allies form a remarkable family, Scutigeridas (fig. 12), in which the antennae are bristle-like and as long as the body, and the legs are extremely long, increasing in length towards the hinder end of the body. The peculiarities FIG. 12. A. Scutigera rv broUneata (after Buffon). B. Tergum and part of a second of the same enlarged to show the position of the stigmata o, o ; p, hinder margin of tergum. of their eyes and respiratory organs have already been referred to above. Most important is the aberrant genus Scolopendrdla, which has lately been shown to have certain marked features indicating alliance to the primitive insects, Thysanura. The species of Scolo- peiwtrella are minute forms five or six mm. in length, appearing (fig. 12), as indicated by the name, at first sight like small Scolo- pcndms (fig. 13). The head and antenna? nearly resemble those of Campodea. The body bears, according to Wood Mason, dorsally fifteen tergites behind the head, the first of these being quite rudi mentary. Ventrally thirteen corresponding indications of somites only can be detected ; and these bear twelve pairs of functional appendages. Two of the tergites appear to be devoid of sternites and appendages. The first post-cephalic appendages ( = third post- orals) are small and turned towards the mouth ; the eleven following ventrally-indicated somites bear each, besides a pair of functional