SUBCLASS 2

subclass 2, notostigma.--chilopods with a series of median dorsal tracheal sacs furnished with tubes dipping into the pericardial blood space, and opening each by an unpaired spiracle upon the 1st, 3rd, 5th, 8th, 10th, 12th and 14th leg-bearing somites. this characteristic is accompanied by the complete disappearance of the tergum of the 7th, either by fusion with that of the 8th or by excalation, and by the evanescence of the terga of the 2nd, 4th, 6th, 9th, 11th and 13th pedigerous somites. the preantennal area of the head is not strongly reflexed inferiorly, and the eyes are large and compound. the maxillae are long and have a sensory organ, the palpognaths are long, spiny and composed of five segments, like the primitive chilopod leg, and the toxicognaths have their basal segments disunited and independently movable. gonopods duplicated in the male. [illustration: fig. 9.--a, _scutigera rubrolineata_ (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.] this subclass contains the single order scutigeromorpha and the family _scutigeridae_. as in the lithobiomorpha there are fifteen pairs of legs, the gonopods are well developed in both sexes and the young is hatched with only seven pairs of legs. the legs and antennae in the adult are extremely long and many jointed. in habits as well as in structure the _scutigeridae_, of which _scutigera_ is the best-known genus, differ greatly from other centipedes. although they hide under stones and logs of wood like _lithobius_, they are not lucifugous but diurnal, and may be seen chasing their foes in the blazing sun. they run with astonishing speed and have the power of dropping their legs when seized. south of about the 40th parallel of north latitude they are universally distributed in suitable localities. in most species the body only reaches a length of about 1 in.; but twice that size or more is reached by examples of the indian species _scutigera longicornis_. [illustration: after latzel, _die myr ost-ung. mon._ vol. i. "chilopoda," vienna, 1880. fig. 10.--gnathites of _scutigera_. i. mandibles. ii. maxillae. iii. palpognaths. iv. toxicognaths.] some fossils of carboniferous age have been described as chilopoda by scudder, who refers them to two families, _gerascutigeridae_ and _eoscolopendridae_. but until the specimens have been examined by zoologists the genera they are alleged to represent cannot be taken seriously into consideration. remains of centipedes closely related to existing forms have been recorded from oligocene beds. (r. i. p.)