The old class, Myriapoda includes the DIPLOPODA, or millipedes, and the CHILOPODA, or centipedes. The present tendency is to raise these groups to the rank of classes. The Diplopoda The DIPLOPODA, or millipedes (fig. 13), are characterized by the presence of two pairs of legs to a segment. The largest of our local myriapods belong to this group. They live in moist places, feeding primarily on decaying vegetable matter, though a few species occasionally attack growing plants. [Illustration: 13. A millipede. After Comstock.] The millipedes are inoffensive and harmless. _Julus terrestris_, and related species, when irritated pour out over the entire body a yellowish secretion which escapes from cutaneous glands. It is volatile, with a pungent odor, and Phisalix (1900) has shown that it is an active poison when injected into the blood of experimental animals. This, however, does not entitle them to be considered as poisonous arthropods, in the sense of this chapter, any more than the toad can be considered poisonous to man because it secretes a venom from its cutaneous glands. The Chilopoda [Illustration: 14. Two common centipedes. (_a_) Lithobius forficatus. After Comstock. (_b_) Scutigera forceps. Natural size; after Howard.] The CHILOPODA, or centipedes (fig. 14), unlike the millipedes, are predaceous forms, and possess well developed poison glands for killing their prey. These glands are at the base of the first pair of legs (fig. 15), which are bent forward so as to be used in holding their prey. The legs terminate in a powerful claw, at the tip of which is the outlet of the poison glands. The poison is a limpid, homogeneous, slightly acid fluid, which precipitates in distilled water. Briot (1904) extracted it from the glands of _Scolopendra morsitans_, a species common in central France, and found that it was actively venomous for the ordinary experimental animals. A rabbit of two kilograms weight received an injection of three cubic centimeters in the vein of the ear and died in a minute. A white rat, weighing forty-eight grams, received one and a half cubic centimeters in the hind leg. There was an almost immediate paralysis of the leg and marked necrosis of the tissues. [Illustration: 15. Mandible of Scolopendra cingulata showing venom gland. After Dubosq.] As for the effect on man, there is little foundation for the fear with which centipedes are regarded. Our native species produce, at most, local symptoms,--sometimes severe local pain and swelling,--but there is no authentic record of fatal results. In the tropics, some of the species attain a large size, _Scolopendra gigantea_ reaching a length of nearly a foot. These forms are justly feared, and there is good evidence that death sometimes, though rarely, results from their bite.