650 THE MICROSCOPE. 



in different groups of insects. In its most complete form, 

 as exemplified in the Butterflies, Moths, Beetles, and many 

 other insects, the metamorphosis takes place in three very 

 distinct stages. In the first, which is called the larva state, 

 the insect has the form of a grub, sometimes furnished 

 with feet, sometimes destitute of those organs. Different 

 forms of insects in this state are popularly known as Cater- 

 pillars, Grubs, and Maggots. During this period of its 

 existence, the whole business of the insect is eating, which 

 it usually does most voraciously, changing its skin repeat- 

 edly, to allow for the rapid increase in its bulk ; and after 

 remaining in this ' form for a certain time, which varies 

 greatly in different species, it passes to the second period 

 of its existence, in which it is denominated a pupa. In 

 this condition the insect is perfectly quiescent, neither 

 eating nor moving. It is sometimes completely enclosed 

 in a horny case, in which the position of the limbs of the 

 future insect is indicated by ridges and prominences ; 

 sometimes covered with a case of a softer consistence, 

 which fits closely round the limbs, as well as the body, 

 thus leaving the former a certain amount of freedom. 

 Pupce of this description are sometimes enclosed within 

 the dried larva skin, which thus forms a horny case for the 

 protection of its tender and helpless inmate. After lying 

 in this manner, with scarcely a sign of life, for a longer or 

 shorter period, the insect, arrived at maturity, bursts from 

 its prison in the full enjoyment of all its faculties. It is 

 then said to be in the imago or perfect state. This meta- 

 morphosis is one of the most remarkable phenomena in 

 the history of insects, and was long regarded as perhaps 

 the most marvellous thing in nature ; although recent 

 researches have shown that the history of many of the 

 lower animals presents us with circumstances equally if 

 not more wonderful, nevertheless the metamorphosis of the 

 higher insects is a phenomenon which cannot fail to arrest 

 our attention. To see the same animal appearing first as 

 a soft worm-like creature, crawling slowly along, and de- 

 vouring everything that comes in its way, and then, after 

 an intermediate period of death-like repose, emerging from 

 its quiescent state, furnished with wings, adorned with 

 brilliant colours, and confined in its choice of food to the 



