CHILO'ONATHA (Latreille), an order of Insects belonging to the class M yriapoda. It has the following characters :—Body generally cylindrical, and consisting of numerous crustaceous rings or segments ; the head is furnished with two short 7-jointed antennae, and two mandibles ; the horny substance of the mandibles does not continue uninterruptedly from the base to the apex, but is divided in the middle so that the upper part is, as it were, hinged to the lower by a tough membrane ; they are covered above by the fore part of the head, which forms a kind of upper lip, and beneath by an under lip ; this last part is divided externally into four portions by threo sutures ; the two central portions are narrower than the outer ones, and spring from a plate of a semicircular shape ; the apex of the under lip is fur nished with several large tubercle& The first segment of the body, or that next the head, is considerably larger than the following seg ments. The legs are short, very numerous, and. terminated by a simple hook ; the anterior segments of the body are some of them unprovided with legs, and others have a single pair each; ing segments (with the exception of the last two or tbreeommencing from the fourth, fifth, or sixth from the head, are each furnished with two pairs of legs. The sexual organs of the male are situated behind
the seventh pair of legs, and those of the female behind the second pair. The respiratory orifices are situated on the sternal part of each segment of the body; they communicate internally with a double series of pneumatic sacs which extend the whole length of the body, and from which the tracheal branches spring and spread over the other organs ; these sacs are not connected with each other, as is usually the case, by a principal trachea. A series of pores on each side of the body have been mistaken for the stigmata, but their orifices give vent to an acid liquid secretion which has a very disa greeable odour, and probably serves as a means of defence.
The Chilognathce crawl slowly, and appear to glide over the ground, and when touched they will roll themselves up spirally. They feed upon decaying animal and vegetable substances. The genus Mats of Linnaeus [Ietrs] included all the species of this order known in his time. It now embraces several genera and upwards of seventy species. [MYRIAPODA.]