76 HISTORY OF INSECTS. 



but from these, insects may at once be distinguished by 

 their being furnished with six legs and four wings ; they 

 also differ in wanting that singular property possessed by 

 crabs and lobsters, of reproducing a limb that has been ac- 

 cidentally lost. The great value of these characters is 

 proved by the importance attached to the exceptions which 

 have been detected ; flies have two of their wings small 

 and imperfect ; butterflies have the first pair of legs unfit- 

 ted for walking ; and a Dr. Heineken thought he found 

 something like a re-production of the antenna? of cock- 

 roaches. The beings, therefore, of which the ' Grammar of 

 Entomology ' professes to treat, are animals which possess 

 an external skeleton, which are provided with four wings 

 and six legs, which cannot re-produce an injured limb, 

 and finally, which arrive at perfection by undergoing meta- 

 morphosis in one or other of the following modes.^ 



1. By passing through an amorphous state, 



AMORPHA ; 



In which the penultimate state is provided neither with 

 mouth nor organs of locomotion ; consequently it neither 

 eats nor moves, nor does it bear any resemblance to the 

 perfect state. This group contains two classes of insects. 



Class I. LEPIDOPTERA ; in which the perfect insect has 

 four fully developed wings, all of them covered with a 

 kind of scales, w r hich are symmetrically arranged on 

 each other, like the scales of a fish or the tiles of a 

 house. The silk-worm, p. 17, and all moths and 

 butterflies, are examples of this class. 



Class II. DIPTERA ', in which the perfect insect has two 

 fully developed wings, and two merely rudimentary 

 ones, which are distinguished by the name of halteres 



