MACHILIS. INSECTS. 245 



ORDER I. THYSANOURA. 



Apterous insects with six feet, not undergoing a metamorphosis ; 

 head distinct ; two antennae, longer than the head ; and the 

 abdomen terminated by filaments or by a forked tail. 



The insects of this order are gnawers, live in retired or covered places, under the 

 bark of trees, stones, or in houses. Many of them appear to be nocturnal. They 

 run very quickly, and leap with facility by means of their tail. Their body is often 

 covered with scales or hairs. 



FAMILY I. LEPISMEN^, Lat. 



Antenna divided from their base into a number of small joints; 

 palpi projecting ; abdomen furnished on each side below with 

 a row of moveable appendages, and long setaceous and joint- 

 ed filaments. 



The body in this family is elongated and covered with small scales, often silvery 

 and brilliant, which has occasioned the most common species to be compared to a 

 small fish. The antennae are long and setaceous. The mouth is composed of a la- 

 brum ; of two almost membranaceous mandibles ; two jaws in two divisions, with a 

 palpus of five or six joints, and a lip with four segments, bearing two palpi with 

 four joints. The thorax is composed of three portions. The abdomen, which is nar- 

 rowed gradually towards its posterior extremity, has along each side of the belly a 

 row of small appendages, the last ones longest, supported on a short joint, and 

 terminated in a bristly point. From the anus arises a kind of scaly stylet, compres- 

 sed and of two pieces, with three articulated bristles, prolonged beyond the body. 

 The feet are short, with the thighs often strongly compressed, and in the form of 

 scales. Many species conceal themselves in window frames which remain shut, or 

 which are but rarely opened, under damp boards, in presses, &c. ; others are found 

 under stones. These insects run very quickly, or leap by means of the filaments 

 of their tail. This family contains two genera. 



Gen. 1. MACHILIS, Lat. Lepisma, Lin. 

 Eyes compound, almost contiguous, and occupying the greater 

 part of the head ; body convex ; abdomen terminated by small 

 setae, proper for leaping, of which that in the middle and placed 

 above the two others is longest ; maxillary palpi very large, 

 and in the form of small feet ; thorax strangulated, the first 

 segment smaller than the second and arched. 



M. polypoda, Lat. Fuliginous brown, with obscure ferruginous 

 spots. Inhabits woods in the temperate and southern parts of 

 Europe. Shaw. vi. pi. 116. 



Gen. 2. LEPISMA, Lin. Forbicina, Geoff. 

 Eyes very small, widely separated, granulated ; body flattened, 

 and terminated by three setae of the same length, inserted on 

 the same line, and not serving for leaping. 



L. saccharina, Lin. About four lines long, of a silvery colour, in- 

 clining to leaden, without spots. Inhabits Europe; originally 

 introduced from America. Shaw, vi. pi. 116. 



L. vittuta, Fab. Body ash-coloured, dotted with blackish, and four 

 longitudinal lines of the same colour Cuv. Reg. An. iii. 161. 



