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•period — the changes commenced in the resting stage continue } 

 other changes, which have gone on at a very slow rate during 

 larval life, become greatly accentuated. A convenient term- 

 ination for this somewhat artificially conceived period is the 

 last larval moult, which discloses the pupa (fig. 7). 



Moulting is initiated by a dorsal splitting of the larval 

 cuticle. Tlie integument of the pupa is covered with minute 

 papillae, v/hich produce a rough surface; and this the pupa 

 employs in freeing itself from the larval cuticle. The actual 

 ecdysis lasts about an hour, and may best be described as 

 taking place by a slow wriggling of the nymph, the larval 

 sheath being gradually pushed farther back. 



The liberated pupa has in many respects the appearance 

 of the adult insect. The general shape and size of the pupa 

 is the same as that of the imago; the antennae, legs, and 

 mouth appendages have attained their full length, but are 

 thick, ''flesliy," and ungainly in appearance. In the female 

 the ovipositor is quite prominent, lying along the median 

 ventral surface of the abdomen. 



So far, then, as the external features are concerned, the 

 most pronounced transformation takes place not in the pupa, 

 but in the resting stage and post-defaecation stages of the 

 larva. I shall describe first the changes in the external 

 appearance of the developing insect as it lies within the 

 larval sheath, and then follow the structures, so produced, as 

 they continue to develop under the cuticle of the last instar 

 — the so-called ''pupal-sheath." Tliis will be followed by an 

 examination of the histological processes which bring about 

 these remarkable external changes; and finally, the internal 

 transformation of the larva will be described. Tliese changes, 

 however, must not be regarded as commencing at, or near, 

 the time of pupa formation ; they have, to a certain degree, 

 been going on during larval life; slowly, indeed, and perhaps 

 even spasmodically, but still they have been going on. Some 

 time before moulting, however, these changes have become 

 accentuated, and others, which have not yet commenced, 

 are now initiated ; but even these are to be regarded only 

 as the result of processes which have gone on in the larva. 



The general shape of the ''living" portion of the feeding 

 larva is identical with that of the larval cuticle which it has 

 secreted, i.e., it is an elongated ovoid maggot, thick in the 

 middle, and gradually tapering at either end. But some 

 time before defaecation starts the integument beneath the 

 cuticle begins to change its general shape ; that of the first 

 two segments begins to round itself off, and, before the larva 

 moults, has transformed itself into the head of the future 

 wasp. A gradual increase or diminution in the size of the 



