606 ARTICULATES. 



Dragon-fly. If by any means any poor, unwary insect, found in the 

 neighborhood of the Ant-lion larva, seems likely to escape, jets 

 of sand arrest his progress, and carry him to the bottom of the 

 pit-fall, where he is instantly seized; his juices sucked out, and 

 the body jerked out of the den, which, if injured, is soon re- 

 paired, and ready for another victim. A plan quite similar to 

 this is also adopted by the larva of a Fly, (Leptis vermileo.) 



The locomotive powers of insects are unsurpassed by those of 

 any other animals. These are peculiarly conspicuous in the 

 Dragon-flies, Termites, Bees and Ants. Even the Swallow is 

 unable, in this respect, to match the Dragon-fly or Darning- 

 needle, which can elude its pursuer by flying backwards and 

 forwards, right and left, without turning its body. Its twenty- 

 four thousand eyes guard it against surprise, by enabling it to 

 see in all directions. The wings of Musquitoes are said to 

 vibrate three thousand times a minute. 



The organs of sense in Insects have a high degree of devel- 

 opment. This is more particularly true of the sight. Of the 

 two kinds of eyes found in adult insects, compound and simple, 

 the latter, termed ocelli, (eyelets,) and stemmata, (stems,) are 

 alone present in the larvse, though these are sometimes entirely 

 without visual organs. In perfect insects, the eyes are com- 

 pound, that is they consist of many eyes, each of which is per- 

 fect in itself, having the proper humors and lenses necessary for 

 the exercise of vision. In addition to the compound eye, which 

 often fills up the largest part of the head, Insects sometimes have 

 simple eyes upon the forehead, generally three in number, set in 

 the form of a triangle, which are suited to view only such ob- 

 jects as are near. The compound eye is immovable, round, 

 oval, or kidney-shaped, and examined under the microscope, ap. 

 pears reticulated, this appearance being occasioned by the hex- 

 agonal lines which bound each eye or lens. The number of 

 lenses, each fitted for vision in its own sphere, is almost incred- 

 ibly great. The number in the Dragon-Fly has already been 

 mentioned ; that of the common Fly is 4,000 ; of the Butterfly, 

 from 6,000 to 30,000 ; and of the Mordella Beetle, 25,000 ; 

 while that of the ant has but fifty lenses. 



There seems no doubt that insects have the sense of hearing, 

 for though the precise organ which is subservient to it has not 

 been fully ascertained, there is abundant evidence that they are 

 guided and influenced by sounds, one of the most striking in- 

 stances of which is that the male of some Insects, such as Cica- 

 da, Crickets, &c., emit peculiar sounds, which attract the fe- 

 males to them. A nocturnal butterfly, Acherontia atropos, pro- 



