ORDER THYSANURA. 157 



3. The Geophilida (united with the latter by Latreille), 

 and having a very great number of equal-sized legs, the 

 body being narrow and almost filiform, each segment bearing 

 two pair of legs. Some species are luminous, as the Geophi- 

 lus electricus. Figures of Geophilus longicornis, and of Li- 

 thobius forcipatus, two British species, serving as types of 

 these two families, will be found in p. 155. 



ORDER in. THYSANURA (Leach, Thysanoures Latreille). 

 This order is distinguished by the more or less cylindric 

 form of the body, provided with only six legs, and destitute of 

 wings, undergoing no other change than an increase of size, 

 and furnished on the under side of the body, at the sides or 

 the extremity, with peculiar organs of motion, consisting, in 

 the family Lepismida, of a double series of moveable appen- 

 dages like false legs, terminated by articulated setae, and in 

 the Poduridee, of an elongated appendage, furcate at the 

 extremity, and applied, when at rest, along the under side of 

 the body. These insects are of small size, and very active, 

 the appendages on the under side of the abdomen enabling 

 them to perform long leaps. They are chiefly found in damp 

 situations under stones, moss, &c. They have been much 

 neglected by naturalists ; but a valuable memoir is published 

 in the first volume of the Transactions of the Entomological 

 Society of London, upon the Irish species, by R. Templeton, 

 Esq., accompanied with beautiful figures. Some of his species, 

 however, appear to me to be established upon insects in the 

 larva state. 



These insects are very interesting, not only on account of 

 their position amongst annulose animals (being regarded by 

 Latreille and Leach as true insects, and by MacLeay as be- 

 longing to a distinct class, Ametabola), but also from the 

 modifications in the structure of the mouth ; some of the 

 species possessing a developement of the trophi as great as 



