354 INSECTA. 



common species has been compared to a little Fish. The antennae 

 are setaceous and usually very long. The mouth is composed of a 

 labrum, of two almost membranous mandibles, of two bipartite jaws, 

 with a palpus consisting of five or six joints, and of a quadri-emar- 

 ginated lip bearing two quadri-articulated palpi. The thorax is 

 formed of three pieces ; the abdomen, which is somewhat narrowed at 

 its posterior extremity, is furnished along each side of the venter 

 with a range of small appendages, supported by a short joint, and ter- 

 minating in silky points, the last of which are the longest ; a sort of 

 scaly compressed stylet, composed of two pieces, issues from the anus; 

 then come the three articulated setae, which are extended beyond 

 the extremity of the body. The feet are short and frequently have 

 very large strongly compressed coxae resembling scales. 



Several species conceal themselves in the cracks in the frame work 

 of windows, under damp boards, in wardrobes, &c. Others retire 

 under stones. 



These Insects run with great velocity ; some of them by means of 

 their caudal appendages are enabled to leap. They are divided into 

 two subgenera. 



MACHILIS, Lat, PETROBIUS, Leach. 



Eyes very compound, almost contiguous, and occupying the greater 

 part of the head ; body convex and arcuated above ; abdomen termi- 

 nated by small threads for saltation, of which the middle one, placed 

 above the two others, is much the longest. 



The maxillary palpi are very large, and have the form of small 

 feet. The thorax is strangulated, the first segment smaller than the 

 second and arched. 



These Insects leap well, and frequent stony and enclosed places. 

 All the species known belong to Europe *. 



LEPISMA, Lin. FORBICINA, Geoff., Leach. 



Eyes very small, widely separated, and composed of a small num- 

 ber of granules ; body flattened, and terminated by three threads of 

 equal length, inserted on the same line, and of no use in leaping. 



Their coxae are very large. Most of the species inhabit the inte- 

 rior of houses. 



L. saccharina; Forbicine plate, Geoff., Insect., II, xx, 3; 

 Schaeff., Elem. Entom., Ixxv. Four lines in length ; of a silvery 

 and somewhat leaden hue, and immaculate ; originally, it is said, 

 from America, now very common in houses in Europe. 



L. vittata. Fab. Body cinereous, dotted with blackish ; four 

 streaks of the same colour along the back of the abdomen. 

 Other species are found under stones. 



* Lepisma polypoda, L. ; L. saccharina, Vill.,- Entom. Lin., IV, xi, I; Roem. 

 Gener. Insect., XXIX, 1 ; Forbicine cylindrique, Geoff. ; Lepisma thezeana, Fab. ; 

 Petrobins maritimus, Leach, Zool. Miscell., CXLV. 



