298 CLASS vin. 



Sub-genera Petrobius, Machilis LEACH. 



Sp. Machilis maritima LATH., M. polypoda DUMER. (not LATE.), Cons. gn. 

 PL 54, fig. 2, &c. Besides the jointed threads (two on most of the seg- 

 ments of the abdomen), GUERIN has observed in Machilis vesicles also on 

 the same segments, which he compares to gills ; Ann. des Sc. nat. sec. 

 Se'rie, Zool. v. pp. 374, 375, Iconogr., Ins. PL n. fig. i f. These animals 

 remind us of larvae of Ephemera. 



Lepisma L. (in part). Antennae inserted amongst eyes, small, 

 remote. Palps moderate. Body depressed, squamose, not saltatory, 

 terminated by three subequal setae. 



Sp. Lepisma sacckarina L., GUERIN Iconogr., Ins. PL 2, fig. 2 ; GEOFFROY 

 Ins. Par. II. PL xx. fig. 3 ; HOOKE Microyraphia 1667, Tab. 33, f. 3, 

 pp. 208 210. It is said that this insect was imported into Europe from 

 America, where it lives in sugar : in Sweden it is rare, according to DK 

 GEER ; it is not spotted, covered with silvery scales, which under the 

 microscope are finely ribbed longitudinally, and differ much in size and 

 form. This insect runs very rapidly, and with us is usually found in 

 clothes -chests, between damp books, &c. 



Sub-genus Lepismina GERV. is distinguished by the body plane, 

 the thorax very broad. 



Sp. Lepisma aurea LE"ON DUFOUR, Ann. des Sc. nat. Tom. xxn. p. 419. Tab. 

 xni. fig. i. 



Note. Genus Nicoletia GERVAIS is distinguished by defect of 

 eyes, and body not scaly ; Campodea WESTWOOD, Ann. of Nat. Hist. 

 Tom. x. 1842, p. 71, by the same characters and by the tail com- 

 posed of two setae only. Is it Podura ambulans L. ? 



Family IV. Podurellce. Body in some elongate, in others globose, 

 broad, covered usually with hairs, sometimes with scales also. 

 Antennae, with few joints, or with four longer joints at the base, at 

 the apex only with short numerous joints. Palps inconspicuous. 

 Abdomen composed of only six or fewer segments, mostly termi- 

 nated by a forked tail, during rest bent forward beneath the 

 abdomen, serving for springing. 



Podura L. 



Spring-tail (properly foot-tail, since the tail is used like feet for 

 motion). They are small insects, which live on trees, under bark, 

 under stones, on moist earth, &c. Some are met with on the surface 

 of water. Since the tail, according to WAGA, is at first wanting 

 in young animals (Ann. de la Soc. Entom. de France, XL quoted by 



