buttp:rfly larvae and their moultings. 17 



An excellent account of the exuviation of the larval skin in Dryas 

 papJiia is given by Buckler, who writes: "I observed the larva in 

 preparation for its last moult, fixed belly upwards to a leaf, on May 

 20th. It remained quite still until noon of the 25th, when I noticed 

 it moving its anterior legs a little free from the leaf, a circumstance 

 which claimed my whole attention ; it was but a slight movement, and 

 was repeated at intervals of about half-an-hour until between 2 and 

 3 o'clock in the afternoon, when it began to stretch its 1st segments 

 downwards from the leaf, making the forepart of the back concave, 

 and then presently gently reversing the movement. It continued thus 

 at short intervals to increase the stretching curve of the body so much 

 that, by 10 minutes past 3, its hold on the leaf was retained only by 

 the fourth pair of ventral prolegs and the anal pair, when, suddenly, 

 the skin snapped asunder close to the head, with quite a shock to the 

 larva, which instantly returned its ventral prolegs to the leaf, whilst 

 the elastic skin, relieved of the tension, was itself, from the impetus of 

 the rupture, gliding backwards. The anterior legs were held back until 

 divested and then returned forwards to their natural position one after 

 the other, but kept just free from the leaf, each pair being elevated in 

 unison for a moment, and let fall as though to test their complete 

 freedom ; otherwise the larva remained passive, the skin only con- 

 tinuing to move backwards, and, whilst passing the ventral prolegs, 

 each foot was lifted up in turn out of it and then replaced on the same 

 spot of the leaf, and, when the old skin had shrivelled up at the end of 

 the body, the larva, with all the ventral prolegs, took two steps forward 

 and drew forth the anal pair free. At the first breaking of the skin 

 the head became exposed, with the old headpiece adhering to the parts 

 around the mouth, but now, at last, the larva gave its head a sudden 

 twist or two, and the old piece fell off. From the rupture of the skin 

 to this final riddance the operation occupied nearly ten minutes ; the 

 spines were all uncovered in a remarkably small, wet and flaccid 

 condition, the front pair even smaller than the others, but now this 

 pair began gradually to grow and in fifteen minutes were far longer 

 than ever, and in another half-hour all the other spines had grown 

 considerably both in length and rigidity. After this the larva remained 

 still for 2|- hours longer." 



With each moult there is usually some change in the appearance, 

 markings, or structure of the larva. Thus, after the first moult, the 

 larva of Apatura iris- develops its long horns, the primary tubercles of 

 the Vanessids appear to be replaced by long spines, etc., whilst, on the 

 other hand, in some of the Pierids and Satyrids, they get smaller, and 

 become almost obsolete. Larvae in which the gradual obsolescence in 

 these tubercles may be well observed are Eiichloe cardamines and Pararge 

 megaera, although almost any members of these families will do. The 

 larva of every species of butterfly will, however, show some modifica- 

 tion or other, and all are exceedingly interesting. 



