840 



. N S E C T. 



in the water ; these, therefore, require to be formed into 

 a distinct division, the preparatory states bearing 1 in 

 fact less resemblance to the imago than those species 

 which are terrestrial in their larva and pupa states, 

 breathing' by spiracles, and greatly resembling the 

 imago. As it is evident, however, that the latter 

 undergo a less decided metamorphosis than the for- 

 mer, we must place the species which have the more 

 decided semi-complete pupa at the head ; indeed 

 Mr MacLeay has separated the others, and applied 

 to their changes the term metamorphosis sub-semi- 

 completa. 



55 



Figs. 32, Larva; 33, Pupa; 34, Imago of Ephemera vulgata. 



The third or total metamorphosis (Met. perfecta of 

 Latreille) consequently consists of the Linnsean groups 

 having incomplete, obtected, and coarctate pupae. 

 These are to be regarded as separate divisions. 

 Amongst these pupae some resemble the perfect insect, 

 but contracted, and as it were destitute of life ; they 

 have limbs, it is true, which are separate from each 

 other, but these limbs, as well as the entire body, are 

 covered with a membranous skin. This covering 

 exists in the other pupae, but is of a firmer consistence, 

 imitating a kind of bark, and to which the term cor- 

 ticata maybe applied, and more completely enclosing 

 the limbs in one general covering. To this kind of 

 metamorphosis, which Latreille considers as compris- 

 ing the obtected and coarctate pupae, he has applied 

 the term pupa obvoluta, observing that the expres- 

 lon obtecta applies to both, and that that of coarctata 



too vague; but surely the structure of the dipterous 

 coarctata pupa (i. e ., an incomplete pupa enclosed in 



f skin of the larva) is much more analogous to the 



;ture of the true incomplete pupa (of which some 



IP", as those of museum beetle, Anthrenus, are 



actually enclosed within the skin of the larva) than it 



the obtected pupa of lepidopterous insects ; in- 



t appears quite evident that if the coarctate 



:tion must be sunk at all, it must be in favour of 

 the incomplete, and not the obtected, section. 



Kip,. M. Larva; 36 Pnp obtecta , 37, Imago of a butterfly 

 v UtppmrcMm piimpMlug) . 



Tlie existence and the number of legs of the larva, 



the permanent or variable form of the head, the com- 

 parative structure of the organs of the mouth with 

 those of the imago, the number of the spiracles and 

 disposition of the tracheae, the moultings of the skin, 

 and the quiescent or active state of the pupa, are all 

 important considerations, upon which the distribution 

 of insects from the characters of their metamorphosis 

 may be effected. 



Hence the Lepidoplera are distinguished by the 

 number of legs, scaly head, &c., of the caterpillar 

 (Eruca. Latreille), and the obtected, or, as Latreille 

 prefers calling it, the mummy-formed pupa (Chrysalis, 

 Latreille) ; the Diptera are distinguished by their 

 worm-like larvae (Vermilarva, Latreille), and their 



Figs. 38, Larva; 39, Pupa coarctata; 40, Imago of Stra'iomy 

 chameleon. 



more or less oviform pupa (Pupa, Latreille) ; the 

 Coleoptera, Hymenoptera, and some Diptera, by the 

 scaly head of the larva (Larva, Latreille), and the 

 disengaged limbs of the pupae (Nympha, Latreille) ; 



Figs. 41, Larva; 42, Pupa incompleta ; 43, Imago of Chrysomela 

 populi. 



and the Orthoptera, Hemiptera, &c., by the active 

 imago-like larva (Demi-larva, Latreille), auo active 

 pupa (Demi-nympha). Thus by an ingenious arrange- 

 ment we have the following distribution of metamor- 

 phosis : 



1. Metamorphosis inchoata, equivalent to the Lin- 



naean section, having complete pupa. 



2. M. dimidiata, semi-complete pupa. 



A. Respiration in larva tracheal. Gryllus, &c. 



(M. semi-complela, Fabricius). 



B. Respiration in larva branchial. Ephera 



(M. sub-semi-completa, MacLeay). 



3. M. perfecta. Preparatory states, Semi-larva and 



Semi-nympha, Latreille. 



A. Pupa with detached limbs, P. incompleta. 



Linnaeus. Preparatory states, Larva and 

 Nympha, Latreille. (Coleoptera, $c.) 



B. Pupa mummy-shaped, P. obtecta, Liilnaeus. 



Preparatory states, Eruca and Chrysalis, 

 Latreille. (Lepidoptera.) 



C. Pupa concealed by an egg-shaped covering, 



formed of the skin of the larva, P. coarctata, 

 Linnaeus. Preparatory states, Vermilarva 

 and Pupa, Latreille. (Diptera.) 



