MO 



principles of the comparative structure of annulos 

 animals. Leaving, therefore, these abstruse bu 

 highly interesting and philosophical topics, our presen 

 inquiry will be directed in tracing the insect throug' 

 its various stages ; first, to a general consideratio 

 of the principles which regulate the metamorphose 

 of insects ; and secondly, to a review oi the pcculia 

 rities exhibited by these animals, in their passage t< 

 the perfect state. To these will naturally succeec 

 thirdly, a general view of the insect structure, espe 

 cially as exhibited in such perfect state, both exter 

 nally and internally ; fourthly, a sketch of their phy 

 Biological and instinctive properties ; and we shal 

 terminate our inquiries by, fifthly, a sketch cf th> 

 classification of the winged insects. 



Section I. On the principles which regulate th 

 metamorpfioset of insects. One of the most remarka 

 ble peculiarities connected with the progressive de 

 velopment of animals, is that for the discovery o 

 which we are indebted to the physiological re- 

 searches of modern comparative anatomists ; namely 

 that animals traverse through a certain series o: 

 grades of development, by means of which they as- 

 cend from the first simple beginnings of life to its 

 highest perfection ; these various grades being evi- 

 dent representatives, or analogies of the perfect 

 states of the still more inferior types of animals. 

 This singular and startling peculiarity is not a fan- 

 ciful theory, but has been the result of the most 

 accurate application of the facts, obtained by the aid 

 of comparative anatomy. And the consequent re- 

 sult of this principle is, that the higher the animal in 

 the chain of creation, the greater number of grades 

 has it to traverse. Not that by this assertion it is 



intended that one animal was, at any period of its 

 existence, a distinct animal, but simply that certain 

 types of form, or various peculiarities of certain in- 

 ternal organisations, which are characteristic of the 

 perfect state of the more inferior animals, are re-pro- 

 duced in those of a higher rank, previous to the ar- 

 rival of the latter at the precise type which is their 

 own. " No one," observes Burmeister, " who speaks 

 of the embryo of man passing through the lower 

 grades of the animal kingdom, can have imagined 

 that man, at any period of his embryo life, was ever 

 an infusory animal polypus, muscle, snail, worm, 

 crab, spider, insect, fish, turtle, snake, lizard, and bird ; 

 but the assertion is nothing more than that man has 

 once, in the progress of his development, been upon 

 that grade upon which the several classes beneath 

 him remain stationary, in the progressive develop- 

 ment of the entire animal kingdom." Now, the most 

 general form of insects is that of an articulated elon- 

 gated body ; but previous to its bursting into life, 

 whilst yet in the egg, its organisation represents that 

 the most inferior animals, having then no other 

 organs than those of nutrition ; when this release is 

 fleeted, we find the animal has now ascended to the 

 lowest types of the articulated structure ; the earth- 

 worm and the leech are strictly represented by 

 those vermiform grubs which have no distinct head, 

 and which belong to the order of two-winged flies, 

 Diptera Will it, we ask, be asserted, that this is 

 H a fanciful idea, confirmed, as it is, by the fact 

 that the dipterous insects, when arrived at the per- 

 ect state, are the least perfectly developed of all 

 5 winged insects. Another grade is attained by 

 those lame, which, although vermiform, are furnished 

 with a distinct head, as the larv of the Hymenoptera, 



INSECT. 



which represent the water Nais ; a third grade is 

 exhibited in those larvae which have the body fur- 

 nished with lateral gills, and reside in tubes ; and a 

 still higher is reached by those larvae which, like the 

 Xereis and Aphrodita, belonging to the Annelida, have 

 a distinct head and legs on the under side of the 

 body. In the following or pupa state, we find some 

 pupae, as those of the gnats, breathing like the crus- 

 tacea, by gills ; others, as those of the moths, buried 

 under ground, like the Myriapoda ; whilst the pupae 

 of butterflies are suspended like the Arachnida, in 

 the open air. The above, which is a brief abstract 

 of the analogies exhibited by Dr. Burmeister, do not, 

 it must be admitted, in some respects possess equally 

 strong grounds for adoption ; but the view of the 

 subject is so novel, that much necessarily remains to 

 be discovered ; and what has yet been adduced, can 

 only be regarded as an approximation towards the 

 truth ; neither can this view of the subject be fully 

 confirmed, until by the aid of comparative anatomy, 

 and by an accurate investigation of the nervous and 

 other systems of animals, the rank of each principal 

 division in the scale of creation has been definitely 

 settled. Still, however, sufficient has been advanced 

 to prove that this view of the subject corroborates 

 the principle already alluded to, that it is owing to the 

 development of wings that the Ptilota, or winged 

 insects, are necessarily subjected to a more complete 

 and astonishing series of transformations, than the 

 other atmulose animals, in which the changes (to 

 which, in fact, in a greater or less degree, all animals 

 are subject) consist in a periodical casting off of the 

 outer envelope. It is true, that in a few insects, 

 which are evident exceptions to the general rules, 



this same mode of moulting takes place ; and it is 

 also to be observed, that during a certain and early 

 period of their existence the same principle exists 

 hroughout the winged tribes of insects which, in 

 such cases, represent in their imperfect state the 

 )erfect state of the other Annulosa. We have al- 

 ready said, that, owing to the external envelope of 

 annulose animals constituting their skeleton, and 

 offering from its stronger consistence a complete ob- 

 stacle to the increase in size of the enclosed animal, 

 t was necessary that this skeleton should, from 

 ime to time, be cast ; we have, however, still to in- 

 quire, how the animal which throws off so important 

 a portion of its organs as its skeleton, can exist, or 

 n what manner a new skeleton is formed. Swani- 

 merdam, in his really wonderful series of observa- 

 ions, discovered, in his endeavours to prove that all 

 nsects were produced from eggs, and that the cater- 

 illar was but an immature butterfly, that, shortly 

 >revious to changing to a chrysalis, the various parts 

 )f the butterfly were found distinctly encased beneath 

 he skin of the caterpillar. And therefore he has 

 aised the theory which has been generally adopted 

 y subsequent authors, that every caterpillar, at its 

 rst exclusion, contains within itself the germe of the 

 uture butterfly, and of all its envelopes, which, suc- 

 essively presenting themselves, are thrown off, till it 

 ttains its perfect winged state. This theory has, 

 owever, been completely opposed by Dr. Herold, 

 distinguished microscopic observer, who, from a 

 most elaborate, indeed, we may affirm, the most ela- 

 orate investigation of the kind, hitherto made, upon 

 ie cabbage-butterfly in its various states, has ar- 

 ;ved at the contrary conclusion that the successive 

 kins of the caterpillar, the pupa case, &c., do not 



