510 THE MICROSCOPE. 



pies the whole width and front of the body. They swim 

 rapidly in the water, with their bellies always directed 

 upwards, rowing themselves along by means of flat- 

 tened hind legs, which are thrown out on each side very 

 much like oars. Hence the Notoneda is generally known 

 as the Boat-fly. It carries the air required for its 

 respiration in a space left for this purpose between the 

 wings and the back, and is a very active and predaceous 

 animal ; when captured some are able to inflict painful 

 wounds with their powerful rostrums. Several species 

 may be met with in almost every piece of water. In the 

 second group, the JVepina, the head is small, triangular, 

 and generally much narrower than the thorax. Their 

 legs are less distinctly formed for swimming than in the 

 preceding group ; but the anterior pair are converted into 

 powerful raptorial organs. 



Nepa cinerea is a British example of this group, met 

 with in every pond ; they respire by means of filaments 

 placed near the caudal extremity, which are so arranged 

 as to be always nearest the surface of the water ; the 

 only available stigmata being situated at the base of 

 these filaments. 



Dytiscus, the principal genus of this tribe, is common in 

 fresh and still waters. Its larva feed upon other aquatic 

 larvae, such as the Gnat, Dragon-fly, &c. The suckers on 

 the legs, the feet, &c., are most interesting objects. 



To the Orthoptera belong Locustina, Gryllina, and Ache- 

 tina, all herbivorous insects. The first is represented by our 

 well-known Grasshopper (Gryllut viridissimus), the second, 

 the Gryllina, appear to frequent trees and shrubs more 

 than the other tribes, the members of which generally 

 keep among herbage ; and, in accordance with this habit, 

 many of the exotic species have wing-cases, which present 

 the most perfect resemblance to leaves both in colour and 

 veination. Of the Achetina, the common Cricket (Acheta 

 domestica), fig. 266, the noisy little denizen of the kitchen- 

 hearth, is the best example. These insects have tho 

 antennae slender and tapering, and often considerably 

 longer than the body. They agree with the Gryllina in 

 the structure of their singing apparatus ; but the wings, 

 instead of being arranged in the form of a high pitched 



