484 



INSECTA. 



IS, witli the body i 

 lit of the body uuro 

 I magniiied. 



four principal divisions, tubercled at its superior edge, the two middle divisions being narrower and 

 shorter, and situated at the upper extremity of another piece, serving as a common base ; the legs are 

 very short, and always terminated by a single claw ; four legs situated immediately beneath the pre- 

 ceding piece of the form of the following, but placed nearer together at the base, with the basal joint 

 proportionately longer, and the majority of the remainder attached, in double pairs, to each of the 

 succeeding joints. The male organs are placed behind the seventh pair of legs, and those of the 

 female behind the second pair. The spiracles are placed alternately above the base of the feet, and of 

 a very small size. 



The Chilogiiatha crawl very slowly, or, as we may rather say, glide along, rolling themselves into a 

 spire or ball. The first segment of the body, and in some also the 

 second, is largest, and represents a corselet, or small shield. It is only 

 at the fourth, fifth, or sixth segment in different species, that the dupli- 

 cation of the legs commences ; the two or four first legs are entirely 

 free to the base, or they do not adhere to their respective segments but 

 ])y a middle or sternal line. The two or three terminal segments are 

 destitute of feet. We observe on each side of the body a series of pores, 

 which had been regarded as spiracles, but which, according to M. Savi, 

 are merely orifices for the discharge of an acid fluid of a disagreeable odour, which appears to serve 

 for the defence of these animals ; the respiratory apertures, discovered by him, are placed upon this 

 sternal piece of each segment, and communicate interiorly with a double series of pneumatic pouches, 

 disposed in a chain throughout the whole length of the body, whence extend trachean branches which 

 are extended upon the other organs. According to M. Strauss, these vesicular trachea; are not con- 

 nected together by a principal trachea, as is customary. 



The form of individuals just hatched is like a kidney, perfectly smooth and without appendages ; 

 eighteen days afterwards they undergo a first moult, when they assnme the adult shape, but they have 

 only twenty-two segments, and the total number of their legs is tyenty-six pairs. M. Savi appears 

 to contradict the assertion of De Geer, that the young have only three pairs of legs and eight rings 

 in the young individuals; but is it certain that the moulting 

 of which Savi speaks is really the first .' — or ought we not, 

 on the contrary, to conclude that these young do not sud- 

 denly pass from a state exhibiting no locomotive organs to 

 one with so many as twenty-six pairs, or in other words, 

 that there are intermediate changes, which have escaped 

 the notice of M. Savi .' Do not the observations of the f;^. 43.-Transfornmtions of luius, from oe ceer. 

 Swedish Reaumur confirm these intermediate changes .' Be this as it may, the eighteen outer legs 

 alone serve for locomotion. At the second moulting the animal exhibits thirty-six pairs, and at 

 the third moult forty-three ; at this time the body consists of thirty segments. In the adult state the 

 male has thirty-nine, and the female sixty-four ; two years afterwards they again moult, at which period 

 the generative organs first appear. From their birth, which takes place in March, until November, 

 when Savi ceased his observations, these changes of the skin took place nearly monthly. In the 

 exuviffi, even the membrane which lines the interior of the elementary canal and tracheae is to be 

 perceived, the organs of the mouth being the only parts wliich M. Savi could not discover. 

 {Osservazioni per servire alia storia di una specie di lulux communissima, Bologna, 1817 ; and another 

 memoir upon lulus fcetidissima, published in 1819, noticed in the Bulletin ofFerussac, December, 1823). 

 These insects feed upon decaying animal and vegetable matter, and they deposit a great number of 

 eggs under ground. According to Linna;us they form the single genus 



luLus, Linn., — 

 which we divide as follows : — 



Some have the body crustaceous, without appendages at the tip, and the antennae thickened towards 

 the extremity. 



[Fam. 1. — Glomerid.e, Westw., or the Onisciformes of Latreille, in the Cours d''Entomoloffie.] 

 Glomeris, Latr., resembles Wood-lice, being of an oval form, and rolling; themselves into a ball ; the body 

 convex above, concave beneath, with a row of small scales along each side of the body beneath, analogous to 

 each of the lateral divisions of the Trilobites. They are only composed of twelve segments, exclusive of the 



