612 



SUPPLEMENT. 



inflicted. No sooner is this operation per- 

 formed, than the ichneumon flies disappear, 

 and the patient remains for an hour in a 

 drowsy and even motionless state, out of which 

 it awakens to feed with its former voracity. 

 It then appears much larger, and its size in- 

 creases every day. Its green colour assumes 

 a deeper hue, and the tints produced by the 

 reflection of the light are more strongly marked. 

 About a fortnight after the worm has been 

 encumbered with this factitious pregnancy, 

 the prospect of a numerous progeny begins to 

 be apparent. By the aid of a microscope the 

 eggs may be seen hatching in the body of the 

 animal ; and as they are all produced at the 

 same instant, a single glance reveals the 

 capada worm covered with a living robe of 

 (larvae of) ichneumon flies. They issue from 

 every pore, all the body being covered with 

 them, only the top of the head appearing bare. 

 Its- colour then changes to dirty white, and the 

 little worms assume a black appearance to the 

 eye, although their true colour is a deep brown. 

 This operation lasts about an hour, and it is 

 followed by another, which is not much more 

 protracted, but still more singular. Immedi- 

 ately that the ichneumon worms are hatched, 

 without quitting the spot where they separate 

 themselves from the eggs, they yield a liquid 

 gum, which becomes solid on exposure to the 

 air. At the same time, and by a simultaneous 

 motion, they elevate themselves on their lower 

 extremities, shake their heads and one half of 

 their bodies, and swing themselves in every 

 direction. And now they commence a very 

 curious operation. Each of these animalcules 

 works himself a small and almost impercepti- 

 ble cocoon in the shape of an egg, in which 

 he wraps himself up. The formation of these 

 cocoons occupies only about two hours, and 

 myriads of them being crowded close together, 

 form a white robe, with which the capada 

 worm appears elegantly and comfortably 

 clothed ; but while they are thus busily array- 

 ing him in his new attire, he remains appar- 

 ently unconscious of their assiduities ; he is then 

 in a state of insect paralysis. As soon as this 

 covering has been completed, and the little 

 artists who wove it have retired to their cells, 

 the worm endeavours to rid himself of his 

 officious guests, and of the robe which con- 

 tains them, but he does not succeed in the at- 

 tempt without the greatest efforts. At length 

 he contrives to get rid of the encumbrance ; 

 but instead of his former fat and shining ap- 

 pearance, he presents all the decrepitude of 

 extreme old age. He is flaccid and dull ; his 

 skin is wrinkled and dirty ; and, in short, 

 symptoms of approaching dissolution begin to 

 show themselves. He still makes a desperate 

 effort to gnaw a few leaves, but he no longer 

 devours them with that voracity which indi- 



cates a vigorous constitution. Shortly after- 

 wards he passes into the state of a chrysalis, 

 and in giving life to thousands of eggs, he 

 relinquishes his own." 



The pupa state of insects is the intermediate 

 stage between the larva and the perfect deve- 

 lopement, and affords many opportunities to 

 the microscopical observer for detecting curi- 

 ous and interesting formations and phenomena. 



" When the larva has attained to its full 

 growth and the parts of the future insect are 

 sufficiently formed beneath its skin, it prepares 

 for its change into the pupa state ; it seeks 

 for a proper place in which to perform the 

 important business. The different methods em- 

 ployed by these little animals to secure this 

 state of rest, may be reduced to four : 1. Some 

 spin webs or cones, in which they inclose 

 themselves. 2. Others conceal themselves in 

 little cells, which they form under ground. 

 3. Some suspend themselves by their posterior 

 extremity ; 4. While others are suspended 

 by a girdle that goes round their body. In 

 proportion as the change into the pupa form 

 approaches, the body is observed often to ex- 

 tend and contract itself ; the hinder part is 

 that which is first disengaged from the larva 

 skin ; when this part of the body is free, the 

 animal contracts and draws it up towards the 

 head ; it then liberates itself in the same man- 

 ner from the two succeedingrings, consequently 

 the insect is now lodged in the fore part of its 

 larva covering : the half which is abandoned 

 remains flaccid and empty, while the forepart 

 is swollen and distended. The animal, by 

 strong efforts, still forcing itself against the 

 fore part of the skin, bursts the skull into three 

 pieces, and forms a longitudinal opening in 

 the three first rings of the body ; through this 

 it proceeds drawing one part after the other, 

 by alternately lengthening and shortening, 

 swelling and contracting the body and differ- 

 ent rings ; or else, by pushing back the 

 exuvia, gets rid of its odious reptile form. The 

 larva, thus stripped from its skin, is what we 

 call the pupa, chrysalis, or aurelia, in which 

 the parts of the future insect are inclosed in a 

 crustaceous covering, but are so soft, that the 

 slightest touch will discompose them. The 

 exterior part of the chrysalis is, at first, ex- 

 ceedingly tender, soft, and partly transparent, 

 being covered with a viscous fluid ; this soon 

 dries up, thickens, and forms a new covering 

 for the animal, capable of resisting external 

 injuries ; a case, which is at the same time 

 the sepulchre of the larva, and the cradle of 

 the insect ; where, as under a veil, this won- 

 derful transformation is carried on. The chrys- 

 alis of the common white butterfly furnishes 

 a most beautiful object for the microscope. 

 Those who are desirous to examine the various 

 members of the insect in its pupa state, should 



