484 



INSECTA. 



Fig. 42. 

 and rUr t 

 the antenna Magnified 



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 Chilognatha 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- 

 ,1 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 

 by a middle or sternal line. The two or three terminal segments are 

 "roM'Slhe'bo^^liedArith 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 tracheae 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 assume the adult shape, but they have 

 only twenty-two segments, and the total number of their legs is twenty-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 ? — oi 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 

 Swedish Reaumur confirm these intermediate changes ? 

 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 



exuviae, even the membrane which lines the interior of the elementarv canal and trachea? is to be 



! 

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



(Osservazioni per servire alia storia di una specie di lulus communissima, Bologna, 1817 ; and another 



memoir upon lulus feet idissima, published in 1819, noticed in the Bulletin of Ferussac, December, 1823). 



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



eggs under ground. According to Linnaeus they form the single genus 



Iulus, Linn., — 

 which we divide as follows : — 



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



the extremity. 



[Fam. 1.— Glomerid.s, Westw., or the Oniseiformes of Latreille, in the Cours d'Entomologie.] 

 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 



Fig. 43. — Transformations of lulus, from De Geer. 



Be this as it may, the eighteen outer legs 



