CABBAGE WHITE BUTTERFLIES 177 



We now resume the history of the Cabbage White. 

 I will next quote Reaumur's account of the method of 

 fixation of the pupa. His pleasant and leisurely 

 narrative easily admits of condensation, and I pro- 

 pose to condense it greatly. Those who prefer the 

 freshness of a discoverer's narrative should read for 

 themselves the ninth, tenth and eleventh memoirs of 

 the first volume of the History of Insects. 



Reaumur first tells us of Butterfly larvae, which like 

 those of the Peacock and small Tortoise-shell, suspend 

 themselves at the approach of pupation by the tail, 

 and hang head downwards. The larva spins a web 

 upon a leaf or other support, crowding the threads 

 towards the centre, so as to form a projection or hill- 

 ock. This web is not easily seen, but it can be made 

 evident by placing a larva ready to pupate in a box 

 lined with black paper. To the hillock the larva 

 applies the hooked claspers at the end of its body, 

 and so gets a safe attachment. The next thing is to 

 cast the larval skin. The soft parts within, covered 

 of course by the thin and flexible pupa-skin, are 

 swollen and contracted by turns until they become 

 loosed from their envelope. The tail-segments are 

 the first to be disengaged ; afterwards the fore part of 

 the body is powerfully distended, and the larval skin 

 cracks longitudinally behind the head, allowing the 

 surface of the pupa to appear. The next step is to 

 slip the loose skin backwards over the body. This is 

 accomplished by the successive contraction and dila- 

 tation of the segments one by one, and is aided by 

 spines or backward-pointing hairs upon the surface of 

 the pupa, which act like a ratchet, and prevent the 



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