OF HARTING. 447 



In the next great division of the order we find the 

 Sugar louse (Lepisma saccharind), also called the 

 Window Fish, a flattish very active little insect, taper- 

 ing gradually from the head to the tail, furnished with 

 three fine caudal hair-like appendages, and wearing a 

 glittering suit of minute silvery scales. It is frequently 

 found in old sugar casks, among damp parchments, 

 disused linen, neglected books, and old papers. " Its 

 immediate allies are the leaping Podurce, or spring- 

 tails, of which we possess several species. One great 

 merit of this genus is that it has suggested to enter- 

 prising manufacturers of children's toys the bright idea 

 which is illustrated in leaping frogs and mice. Indeed, 

 the mechanical contrivance by means of which the 

 leaps of these mimic animals are effected, is but a rude 

 copy of the distinguishing character of Podura. This 

 consists of a forked process at the extremity of the 

 abdomen, which in its normal position is bent forwards 

 under the body, but when the insect is disturbed, it 

 suddenly presses the forked and elastic tip of this 

 organ against the surface on which it is standing, and, 

 forcibly unbending it, instantly springs upwards several 

 inches and alights at a considerable distance. A very 

 common species (P. Aquatica), a tiny black speck of 

 insect life, is enabled, with the assistance of this simple 

 apparatus, to leap on the surface of water with as 

 much ease and agility as the other species on more 

 solid surfaces. Like the Lepisma, many of the Podurce 

 are clothed with scales, and the latter, mounted sepa- 

 rately as test objects for the microscope, are well 

 known to students of Natural History, but a magnified 

 specimen of the insect itself, properly illuminated, is 

 indescribably beautiful, the rich play of colours from 

 its iridescent scales producing a gorgeous effect. 



It will perhaps be recollected that the term Insect, 

 as applied to an invertebrated animal with articulated 

 limbs, simply implies one whose body is composed of 

 rings or segments ; but the class Insecta, as at present 



