Page:The New International Encyclopædia 1st ed. v. 14.djvu/241

MYBIAPODA. 203 MYBIAPODA. FORMS OF MYR1AP0D8. 1. Oeopliilas. 2. Polydesmus. 3. Julus. MYB'IAP'ODA (Neo-Lat. nom. pi., from JIGk. ixvpilmovi, ini/riopous, having ten thousand feet, from Gk. fivptoi, ini/iioi, ten tlionsand + irous, pous, foot). A chs3 of artliropoils resem- bling annelids in their lengthened form, and in the great number of equal, or nearly equal, seg- ments of which the body is composed ; but in most of their other characters more nearly agree- ing with insects, among which they were ranked by the earlier naturalists. They differ from insects and all other arthropods in the fact that the posterior segments of the body bear jointed locomotor appendages. In addition to their affinities with insects, myriapods are worm-like and some of them suggest relations with the thy- sanurans. They have a distinct head, but there is no distinction of the other segments, as in insects, into thorax and abdomen. They have simple or compound eyes ; a few are destitute of eyes. They have antenna; like those of insects. The mouth is furnished with a complex masticat- ing apparatus, in some resembling that of some insects in a lan'al state, in others similar to that of crustaceans. Kespiration is carried on through minute pores or spiracles, placed on each side along the entire length of the body, the air being distributed bj^ innumerable ramifying air-tubes to all parts. In most parts of their internal organization the myriapods rcsemlile insects, although a decided inferiority is exhib- ited, particularly in the less perfect concentra- tion of the nervous system. The resemblance is greater to insects in their larval than in their perfect state. The body of the myriapods is pro- tected by a hard chitinous covering. The number of segments is various, seldom fewer than 24, although in some of the genera they are con- solidated together in pairs, so that each pair, unless closely examined, might be considered as one segment bearing two pairs of feet. The legs of some of the lower kinds, as Julus, are very numerous, and may be regarded as intermediate between the bristle-like appendages wdiich serve many annelids as organs of locomotion and the distinctly articulated legs of inscct.s. In the higher myriapods, as Scolopendra, the legs are much fewer, and articulated like those of insects. Some of them feed on decaying organic nuitter, chiefly vegetable; those of higher organization are carnivorous. The myriapods do not luidergo marked metamorphoses, Init the yoinig greatlv resemble the adults, although some of them are at first quite destitute of feet: and, contrary to what takes place in insects, the body becomes more elongated as maturity is approached — the nmnber of segments and of feet increase, Myriapods are widely distributed, and are rep- n-^ented in almost every ])art of the earth. They flourish in moist and dry. hot and cold climates. Like other widely distributed animals, they show great variation in size and color, ranging from microscopic size to a length of more than six inches. Some of the .Julid:^ and PolydesmidiP of the tropics are beautifully and brilliantlj' col- VOL. XIV.— n. ored. Some of the species of Geophilus are phos- phorescent. Most myriapods inhabit dark and obscure places. Some of the cave-inhabiting species from Wyandotte and Bradford caves in Indiana are described by Packard as light in color, and those from the latter cave have rudi- mentary eyes. The organs of defense throughout the class vary greatly. In the centipedes the large claws, supplied with poison from a gland, are weapons of offense and defense. The milli- pedes, on the other hand, rely for defense on an acid secretion from certain glands. Other forms are hairy or bristly. Hairiness was the most common mode of defense among fossil myriapods. A fossil bristled myriapod has been found in America in Paleozoic strata, and two species have been found in the Old Red Sandstone of Scot- land. The highest vertebrates in this deposit are fishes, and the highest plants are conifers. The Paleozoic species, about forty in number, all be- long to an extinct order ( Archipolypoda) and most of them were of gigantic size. Later fossil m3'riapods, contemporaneous with giant fossil Amphibia, occur in the coal measures. One of these forms from Illinois approaches very closely the Julida; of to-day. Only one species has been found in the chalk layers, but in Ter- tiary and recent times plentiful remains have been found. The majority of these belong to the Chilognatha and Chilojjoda, They have been found in the gypsum of France, in the broMn coal of Germany, and in the Green River formation of North America, Amber has also yielded sev- eral species. Classification. The class Myriapoda is now divided into five orders, the Chilognatha or Dip- lopoda, the Chilopoda or Syngnatha, the Sehizo- tarsia, the Symphyla, and the Pauro[)oda, To the Chilopoda belong the common thousand-legs of the family .Julid.-e, as well as the representatives of seven other families, all of which bear two pairs of legs to each of the body segments except the first three, Verloef states that the males of some of the Julid;T undergo certain seasonal changes. In the spring and autumn the form of the legs and other organs changes. These sea- sonal changes are correlated with the sexual condition of the .Julus just as the males of cer- tain birds and fishes show a brighter coloration and other changes at the breeding season, .Julus will feed freely in captivity if the earth is kept at the proper moisture and iiroper food is fur- nished plentifully. They will thrive on grass, leaves, and bits of apple and pear. The eggs are numerous, from GO to 100 being deposited at a laying. The female forms a receptacle for the eggs some distance below the surface of the ground. It is in the shape of a hollow sphere, and is composed of little pellets of mud. which are molded by her jaws and front legs. The nest is perfectly smooth within, but the outside is rough and shows the pellet composition. In the top of the sphere a small 0])ening is left until the eggs are laid. The hole is then plugged up with earth and the eggs are left to chance. The chilopods have many-jointed antenna> and only one pair of legs to each joint. To this group be- long the large tropical centipedes of the family Scolopendrida> and the long slender Geo|iliilid:c, as well as the Lithobilidse and Notophilid^. The order Schizotarsia contains but a single family, the Scutigeridn>. of which the common household centipede of the L'nited States {Scuti-