38 



PSYCHE. 



[March 1S91. 



this exception, and also when it is noted 

 that an extra quiescent larval stage may 

 occur in the second sei'ies of orders, as 

 in some beetles, whose extraordinary 

 habits render two quiescent stages es- 

 sential in their development. 



It is a remarkable fact that, as a rule, 

 the larvae of the second or specialized 

 series of orders have the habit of feeding 

 voraciously. In this way the larvae 

 store up fats and food matters in their 

 own bodies in preparation for the qui- 

 escent and helpless pupal stage, during 

 which they live upon these accumula- 

 tions, they being taken up by the cells 

 of the tissues and used in building up 

 the organs and parts of the adult. The 

 pupal stage is passed, as a rule, in more 

 or less sheltered situations, and it is 

 either enclosed in a special covering, a 

 cocoon, woven by the animal, or else 

 protected by one acquired through the 

 moulting and hardening of its own cut- 

 icle. The difference between this last 

 and the ordinary process of moulting 

 consists in the retention of the moulted 

 skin, the animal shrinking within it for 

 shelter as its fatty parts are consumed, 

 instead of casting it off altogether. 



Lubbock, in his Origin and meta- 

 morphoses of insects, has shown that 

 the inactivity of the pupa in the second 

 series of orders is not a novel condi- 

 tion, but a mere prolongation of the 

 shorter periods of inactivity which ne- 

 cessarily accompany every change of 

 skin or moult. These facts and the ob- 

 vious want of any common structural 

 differences in the quiescent pupae, as 

 compared with the similar stages of ac- 



tive pupae, show that quiescence must 

 be reckoned as a habit of resting from 

 active exertion during a more or less 

 prolonged period of their growth which 

 has been acquired by the more special- 

 ized forms of insects, not only generally 

 among the members of the second series 

 of orders, but also by many among the 

 first series. The degraded larvae of in- 

 dividuals in these specialized forms are 

 as a rule farther removed structurally 

 from their own adults, than in forms 

 having a direct mode of development, 

 and the changes to be gone through be- 

 fore reaching the adult stage are greater 

 and more numerous. The habits of the 

 animal during the pupal stage have con- 

 sequently changed in proportion to 

 these requirements from the active to 

 the quiescent condition. 



There ai"e other series of facts equally 

 important and significant. While the 

 Thysanuriform stage is present more or 

 less in Coleoptera and Neuroptera, 

 which have the indirect mode of develop- 

 ment, it is absent in the orders from 

 XII to XVI inclusive, having been re- 

 placed by the secondary larval stages in 

 accordance with the law of acceleration 

 in development. 



The tendency of the more specialized 

 forms in the orders I to IX to accelerate 

 the development of the earliest stages is 

 shown in various ways. In the grass, 

 hoppers,* Mantidae, etc., the inheri- 

 tance of the adult peculiarities of the 

 type affects the young at such early 



* Packard's illustrations on p. 60 of his Entomology 

 for beginners give an excellent series of one species, 

 Caloptenus femur- rubrum 



