70 LONDON INSECTS 



The first are spoken of in scientific books as 

 ' Haustellate,' the last as * Mandibulate,' but as this 

 arrangement only gives two classes, it is not of much 

 use. Another way of dividing them is according to 

 the changes which they pass through before reaching 

 the perfect state. 



Moths and Butterflies, and the many other insects 

 which, before they can fly, are at one time Caterpillars, 

 or Grubs of some kind, and at another Chrysalises 

 each stage to all appearance quite unlike the others 

 are classed as undergoing 'complete metamorphosis,' 

 and are called Metabola. 



Others, such as Earwigs, Green Flies, and Cock- 

 roaches, which pass through less startling changes, 

 are classed as undergoing either 'incomplete' or 'no 

 metamorphosis ' Hemimetabola or Ametabola. 



The difference between the three classes thus divided 

 seems very wide, but is, in reality, less than it appears 

 at first sight. It lies mainly in the difference in the 

 stage of growth at which the insect is born or hatched. 



The ' unchanging,' or only ' partially changing,' 

 insects leave the egg in more or less advanced stages 

 of development, and reach the perfect state rather by 

 gradual growth than by any sudden alterations of 

 form; while those described as undergoing 'complete 

 metamorphosis ' are first hatched in such an imperfect 

 form that, after eating and growing for a time, they 

 are practically sent back again to the egg. In this 

 second torpid egg-stage the soft fleshy parts are 

 hardened, and wings and other high organs developed, 



