INSECT. 



839 



the course of the summer, and arriving at the perfect 

 state in the autumn ; or else passing the winter in 

 the chrysalis state, and bursting forth as perfect insects 

 in the spring, and then depositing eggs, the progeny 

 of which will not require to undergo their change to 

 pupae until the autumn : the duration of the larva 

 state of these latter will therefore necessarily be longer 

 than in the former ; but there are exceptions to these 

 rules ; thus, in many species there are many genera- 

 tions in a year, as in the Aphides and the flesh-flies ; 

 whilst, on the other hand, some larvse, as those of the 

 goat-moth and cockchafer, require three years before 

 they attain their full growth, and the stag-beetle is 

 stated by Rosel to extend to six years. 



Having at length attained its full size, the larva is 

 now to undergo a change more important than any to 

 which it has hitherto been subject. 



III. The Pupa. The change to which we 

 alluded at the close of our last section consists in 

 another shedding of the outer skin, when the insect 

 appears in a totally different form, during the period 

 of which it is destined to remain in inactivity and 

 liable to destruction, were it not for the admirable 

 instinct which is exhibited by the larva before its 

 change, in the construction of a case or cocoon 

 wherein it is safely lodged until its final assumption 

 of the perfect state. We have already, in our article 

 COCOON, given a general statement of the proceedings 

 of the cocoon-forming caterpillars. There are also 

 many larvae which, although the pupae are inactive 

 do not construct cocoons, but merely secrete them- 

 selves in some obscure situation, or bury themselves 

 under ground, where they hollow out a narro\v 

 cave for their repose. Others again, as detailed in 

 our article BUTTERFLY, suspend themselves in the 

 open air. Another class, as described in our article 

 DIPTERA, retain their larva skin within which thej 

 become pupae. This period of inactivity is not, how 

 ever, universal, since there are many insects which 

 retain their activity, and therefore need no cocoon 

 for their defence. This is the case with the grass 

 hopper, cockroach, Cimex, Cicada, and others. 



The state to which the insect is now arrived i 

 technically termed the pupa ; and it is this terrr 

 which we must be compelled to make use of in speak 

 inar of the present state of insects, since there is n 

 English word applicable to pupa? in general. Th 

 terms Chrysalis and Aurclits having indeed been ap 

 plied to the pupae of Lepidoptera, and that of nymp 

 partially to other pupae. 



The variations which exist in the pupse of the dil 

 ferent groups of insects are much more striking tha 

 those observable in the larvae ; hence it is not sur 

 prising that Fabricius and his followers employed th 

 name which characterises the pupa to designate th 

 general nature of the metamorphosis, a decided! 

 incorrect mode of proceeding ; since by this mean 

 the metamorphosis of an insect is said to be perfec 

 when the pupa state is perfect (that is, active, an 

 resembling the perfect insect, except in wantin 

 wings) ; whereas it must be evident that this kind o 

 metamorphosis must, as compared with other species 

 be the least perfect or complete ; and, on the othe 

 hand, the imperfect metamorphosis, or that havin 

 the most imperfect pupa, must for the same reason b 

 the most complete and perfect change which any 

 the insects undergo. 



Linnseus first applied these and similar terms, an 

 most appropriately, to designate the variations, not o 

 tlie nature of the metamorphosis, but of the pupa. 



hey were as follows : 



1. Pupa completa, active, with all the parts of the 



perfect insect. Example, Aranea, Acarus, 

 Oniscus. 



2. Pupa semicomplcta, active, resembling the parent, 



but having only rudiments of wings. Example, 

 Gryllus, Cicada, Cimex, Libellula, Ephemera. . 



3. Pupa incompleta, inactive, but with rudimental 



wings and legs. Example, Apis, Formica, 

 Tipu/a. 



4. Pupa obtecta, with the thorax and abdomen dis- 



tinct, enclosed in a scaly covering, i. e., corti- 

 cata, and either naked or enclosed in a cocoon. 

 Example, Lepidoptera. 



5. Pupa coarctata, enclosed within a globular or 



oval case, formed of the skin of the larva. 



Example, Musca, (Estrut. 



Now the true winged insects necessarily suffer 

 only the four latter species of metamorphosis ; although 

 n those species of the semicomplete kind, which have 

 no wings in the perfect state, it may with equal pro- 

 priety be said that they belong to the first section in 

 which the pupa is complete; these, however, must be 

 regarded only as exceptions, belonging in reality to 

 the second and not to the first section. Latreille, to 

 whom entomology is so much indebted, distinguishes 

 three species of metamorphosis, to which, with a view 

 to obviate the difficulties arising from the Fabrician 

 mode of nomenclature, he has applied a different 

 series of names,calling the first Metamorphosis inchoate, 

 dimidiata, and perfccta. The first of these terms is 

 applied to wingless insects, such as the ScolopendrtE, 

 lull, &c.,and in which the variations of the larva and 

 pupa states are so indistinct that the terms cannot 

 with propriety be employed, the metamorphosis con- 

 sisting occasionally of an increase in the number of 

 liinbs and rings (figs. 27, 28, magnified ; and 29, 



natural size, representing the growth of an lulus). 

 In the species undergoing the metamorphosis dimi- 

 diata, the differences are more observable ; the larva 

 (demi-larva, Latreille) is apterous, but the pupa 

 (demi-nymphe, Latreille) is furnished with the rudi- 

 ments of wings. This division, therefore, corresponds 

 with the section Pupa semicomplcta of Linnaeus, or 

 the Metanwrplwis semi-completa of Fabricius. 



Fio- 30 Larva; 31, Pupa of the great green English grasshopper, 

 'see Article GRASSHOPPER, for figure of its Imago. 



The Hemiptera, Orthoptera, and many Neuroptera, 

 undergo this kind of transformation ; but amongst 

 the latter there are some and they are chiefly aquatic, 

 such as the dragon-flies and may-flies which are fur- 

 nished with anal or lateral plates or gills for breathing 



