TIIYSANOURA. 



487 



THE raiST FAMILY OF THE TIIYSANOURA,— 

 Lepismkn/e, Latr., 



Has the antenna? like threads, and divided, from the base, into a great number of minute joints; i)alpi 

 very distinct and exposed ; the abdomen furnished on each side, beneath, -nith a row of moveable 

 appendages, like false legs, and terminated by articulated setse, of which three are more remarkable; 

 and the body is clothed with minute, shining scales. It composes the single genus 



Lepisma, Linn., — - 



"Which has the body elongated, and covered with small scales, silvery and shiidng, whence (lie most 

 common species has been compared to a small fish. The antennse are setaceous, and often very long. 

 The moutli is composed of a lal)rum, two nearly membranous mandibles, two maxillae, with two divi- 

 sions, having a 5 or 6-jointed palpus, and a labium with four divisions, bearing two 4-jointcd palpi. 

 The thorax is composed of three segments. The altdomen, which is gradually narrow^ed towards its 

 posterior extremity, has, at the sides, a row of small appendages arising from a short joint, and ternd- 

 nated in setose points : the posterior are the longest. A kind of scaly style, com|iressed, and formed of 

 two pieces, arises from the anus; then follow tliree articnlated set.x, wldeh extend lieyond the body. 

 The legs arc short, with the coxjg often very large, and strongly compressed and scale-like. 



Many species hide themselves in the crevices of saslies whicli remain closed, or are but rarely opened, 

 under damp boards, in wardrobes, &c. Others lie hidden uiider stones. 



Machilts, Latr. (Pelvvliiv.s, Leach), has the eyes very much facetted, 

 ' nearly contiguous, and occupying nearly all tlie heail; the body convex, 

 ai'ched above ; the abdomen terminated by small threads fitted for leaping, 

 the middle one placed above the other two, beinj^; much longer than 

 them. They leap very well, and frequent stony places. The species 

 are entirely European. Leplsuta pob/poda, Linn., &c. ; Petrobius mari- 

 timus. Leach. 



Lepisma, Linn. {Forhlcina, Geoff.), has the eyes very small, wide apart, composed of a small number of grains ; 

 the body flat, and terminated by three threads of equal length, inserted in the same line, and not lifted fur leaping; 

 the coxte very large. The majority of the species are found in the interior of houses. Lcp. saccharina, Linn., 

 four lines long, of a leaden, silvery colour, without spots, said to be a native of America, and other species. 



Fig. 47. — Mfichilis jjolypoJa. 



THE SECOND FAMILY OF THE TIIYSANOURA,— 



PODURELL.E, Latr., 



ILiTcthe aiitennre composed of four joints; the mouth not exhiliitiug distinct and cxsertcd paipi, and 

 (if whicli tlic abdomen is terminated ijy a furcate tail, applied, in inaction, against the hclly, and used 

 in leaping. These, also, only form the single genus 



PoDURA, Linn. 



These insects are very small, soft, elongated, with the head oval, .ind two eyes, each formed of eight 

 minute tuhcrclcs. The legs have only four distinct joints. The tail is soft, flexi!i!e, and composed of 

 a basal piece, moveable at its insertion, and tenninatcd by two branches i'orming the prongs of the fork, 

 which are capable of opening and shutting. They can unfold their tail, striking it with foice against 

 the plane of position, and thus raising themselves into the air, and leaping hke the Fleas, but to a more 

 moderate height. 



Some species are found upon trees and plants, or beneath bark or stones, and sometimes upon the 

 snow itself, at the time of a thaw. Many species unite into numerous societies, upon the earth, in 

 sandy paths, and resemble, at a distance, a small quantity of gunpowder. The propagation of some 

 species appears to take place in the winter. 



Podura, Linn., has the antennie of cfi'.ial thickness throughout, without minute, 

 jnints at the tip; the body is linear or cylindrical, with the thorax distinctly articu- ' 

 lilted and the abdomen narrow and oblong. Podura arborca, Ijiaw.; P.aquatiea, 



Linn., &c. 



Smiinthunis, Latr., has the antennas slenderer at the tip, and terminated by an 

 annuiated joint; the thorax and abdomen form a g-lobular or oval mass. Podura ^ 



uira, Linn., S;c. 



