EECBEATIVE SCIENCE. 



SI 



bursts down tlie back and at the liead, and 

 with, exertion the insect frees itself entirely 

 from its skin. It has now attained what is 

 called the chrysalis, or pupa, state, though 

 the change is not yet completed ; for it will 

 be seen that when the skin is separated, that 

 the legs and antennae, as well as the wings, 

 are separate from the body, but, after a few 

 seconds, the pupa makes several powerful 

 respiratory efforts. During this period the 

 abdominal segments become more contracted, 

 the wings, though small, are enlarged and 

 extended along the sides and under part of 

 the body. When the skin is being thrown 

 off there is exuded beneath it a peculiar 

 transparent fluid, which facilitated its re- 

 moval. This fluid, which is diffused over the 

 whole body, and amongst the limbs, soon be- 

 comes thickened by evaporation, and when 

 it is quite dry it unites the limbs and wings 

 to the sides of the body, forming a compact, 

 hard, horn-like covering to the whole. The 

 change is now completed, and the pupa per- 

 fectly formed. Thus we have seen that the 

 minute eggs, after a certain period, become 

 hatched, and a small caterpillar is formed, 

 which feeds upon the grosser substance of 

 the nettle, and that after it has attained its 

 full growth it enters upon its pupa state, 

 having acquired a very different form, and 

 some new external organs, and at the same 

 time its internal organization has undergone 

 a fresh arrangement. The pupa now remains 

 in a state of perfect quiescence, and con- 

 tinues tlius in an entire abstinence from all 

 food for a variable period, which appears to 

 depend upon the heat of the weather, or 

 other external circumstances. Thus, if the 

 lava changes into the pupa state, in the middle 

 of summer it becomes transformed into the 

 perfect butterfly in from eight to ten days ; if, 

 however, this change takes place in the earlier 

 and cooler part of summer, it remains in that 

 state about fourteen days, but if it enters the 

 pupa state towards the end of summer, when 

 the temperature of the atmosphere is daily 



declining, it remains in that state through 

 the cold of winter until the return of genial 

 spring sets in. It has been proved by 

 Eeaumur that if the pupa is placed in an 

 ice-house, its development into the perfect 

 butterfly may be retarded for two or three 

 years ; on the other hand, if some of the 

 pupa of the same age be placed in a hot- 

 house, even in the midst of winter, they 

 become developed into the perfect insect in 

 from ten to fourteen days. A certain period 

 of repose is, however, absolutely necessary, 

 for the insect now undergoes an entire change 

 of form and habit, and its internal structure 

 is metamorphosed to enable it to perform the 

 new functions for which it is destined, for, 

 from the change which its body has gone 

 through, it is now unable to enjoy those 

 pleasures which it did in its previous state. 

 A short time before the pupa changes into 

 the perfect insect, all the external parts are 

 seen to be more developed ; it becomes rest- 

 less, and moves about more vigorously ; at 

 length it bursts its case, and speedily dis- 

 engages itself, stands on the outside of its 

 late prison with the wings dependent; it then 

 makes several powerful respiratory efforts. 

 At each respiration the wings may be seen to 

 become more expanded and larger, which is 

 caused by the enlargement and extension of 

 the air-tubes, and their accompanying cir- 

 culating vessels which ramify through them. 

 In a very short time these organs attain 

 their full development both of beauty and 

 form ; the insect then remains at rest for 

 several hours to gain strength, and for the 

 hardening and consolidation of the rest of 

 the body ; it then takes to flight, but how- 

 changed in form, how different in habit ! 



The form of the .insect is now so totally 

 changed, that it would be diflicult to believe 

 it the same creature unless we had watched 

 it in its different states and changes, for now, 

 from its being a disagreeable and repulsive 

 creeping creature, which few people admire 

 or cherish, feeding and grovelling upon the 



