TEANSFOIIMATION OF INSECTS. 339 



species of the animal kingdom, has two chief divisions. In the one, 

 the Ametabola, we have an imperfect, in the other, the Metabola, a 

 perfect metamorphosis ; that is, in the former there is no quiescent 

 pupa state, and the metamorphosis is accompanied by no striking 

 change of form ; in the latter there is an inactive pupa that takes no 

 nourishment, and so great a change of form, that only by watching 

 the progress of the metamorphosis can we recognise the pupa and the 

 imago as belonging to the same animal. The Metabola correspond, 

 as it were, to the flowering plants ; the Ametabola to the Cryptogamia. 

 It is well worthy of remark, that among plants the Cryptogamia, and 

 among insects the Ametabola, first appeared on our earth. The most 

 ancient forests, composed of tree-ferns, club-mosses, and equisetse, were 

 inhabited by Locustce and Blattce, the first insects. " There have not 

 yet been found," says Professor Heer, in his Sistory of Insects, " in the 

 carboniferous and triassic rocks any traces of insects that can be with 

 certainty referred to any of the other insect orders." 



The degree of this metamorphosis is, however, very different in dif- 

 ferent 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 caterpillars, grubs, and maggots. Dur- 

 ing this period of its existence the whole business of the insect is eating, 

 which it usually does most voraciously, changing its skin repeatedly 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. Pupse of this 

 description are sometimes enclosed within the dried larva skin, which 

 then forms a homy 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 metamoi-phosis is one of the 

 most remarkable phenomena in the history of insects, and was long 



