12 THYSANOURJE OF THE UNITED STATES. 



abdomen beneath with an appendage for leaping ; 

 tail with three styles of which one is above the others. 



Species. — M. ^variabilis. Superior caudal pro- 

 cess more than double the length of the others ; false 

 feet bisetous at tip ; colour cinereous or iridescent 

 varied with black. 



Inhabits North America. 



Cabinet of the Academy. 



Body above cinereous, somewhat iridescent, varied 

 with black; gibbous portion of the body not differently 

 coloured; a more or less regular whitish vitta ; Jalse 

 feet white, hirsute, setaceous at tip; superior caudal 

 process more than double the length of the inferior 

 ones. 



Far. a. Body above unicolor, destitute of the 

 white dorsal vitta. 



Var. b. Body ferruginous, with dusky lateral 

 spots. 



Var. c. Body with several snowy spots each side. 



A common insect in many humid places, probably 

 in almost every temperate part of North America. 

 We observed it as far south as East Florida. It is 

 subject to a great many variations. 



Genus — Podura. 



Antennae four jointed, filiform, terminal joint en- 

 tire ; body cylindrical ; trunk distinct. 



Species. — l.P. *fasciata. Body yellowish- white 

 with four distant black bands ; tail black ; bands 



