158 AMETABOLA. 



in the most perfectly mandibulated insects ; whilst in others 

 the mouth is so obscurely organized, that neither Latreille, 

 Savigny, nor Templeton have been able to trace its forma- 

 tion. In some species the eyes are merely rudimental ocelli, 

 but in others they are perfectly reticulated. I may also 

 specially notice the beautiful scales with which the body is 

 covered, and the apparent want of spiracles along the sides 

 of the body, and which Latreille, notwithstanding a very 

 minute examination, was unable to discover. M. Guerin has, 

 however, very recently presented to the French Academic 

 des Sciences a memoir, in which he announces the existence 

 of branchiae'' in one of the species of this order. They are 

 placed under the abdominal segments, and by the side of 

 those appendages which are compared to the false legs of 

 the Crustacea. They are inclosed in little membranous bags 

 of a similar organization to those of the respirator}' organs 

 of a great number of the inferior Crustacea. This discovery 

 of branchiae in these insects appears important in various 

 respects, and more especially because it establishes a link be- 

 tween two classes hitherto regarded as certainly separate as 

 regards their mode of respiration. 



This order is composed of two families : 



1. The Lepismida, having the antennae setaceous, divided 

 from the base into a great number of small joints ; the palpi 

 are distinct and exserted ; the abdomen furnished at the sides 

 with a series of moveable appendages like false legs, termi- 

 nated by articulated setae, three of which are of a larger size 

 than the rest. (PL 1. Petrobius maritimus.) 



These insects are extremely active, running and leaping 

 with great agility ; some are found under stones, and in moss 

 in dam]) situations, whilst others, as the sugar louse (Lepisma 

 saccharina), frequent houses. 



2. The Poduridte, having the antennae composed of four 

 joints ; the palpi are not distinct, and the abdomen is not pro- 



