130 London Insects. 



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, 

 of which there were no traces when the insect left 

 the first egg. When this is done the chrysalis skin 

 is cracked and thrown aside as useless, like the 

 eggshell of a Chicken. The difference between 

 insects undergoing " no metamorphosis " and those 

 undergoing " partial metamorphosis " is merely in 

 the stage of advancement in which the egg is left. 

 Both leave it in a more developed condition than 

 the classes of insects undergoing "complete meta- 

 morphosis." 



