32 BRITISH LEPIDOPTERA. 



extended on account of the lack of freedom of the femora-tibial arti- 

 culation ; the femur preserves its direction from behind forwards ; and 

 the knee, in the first two pairs, remains at the same height. The wings 

 overlie then and cover the underside of the two basal abdominal 

 segments. Their surfaces, in becoming united, increase much in 

 size." Gonin further states that the positions which the organs assume 

 are determined in advance, and that the structure of the hypodermis is 

 specially modified in all the parts which remain external. He also 

 notes that if, during transformation, the chitinous mask (larval head) 

 be separated from the integument beneath, the antennae and tongue 

 will not be fully extended. The position taken up by the organs is 

 due to the fact that, as the larval skin moves back, it preserves sufficient 

 adherence to the organs beneath to draw them after it in the direction 

 of the abdomen. 



Chapman observes that at the larval-pupal moult, the head of the 

 larva of Sphinx lic/ustri splits, and remains attached to the skin by its 

 labial margin. The effete larval head is packed tightly' with the new 

 pupal mouth-parts and antennae (chiefly the latter), coiled and folded 

 up. At the moult, as the head slides down the venter, it pays out the 

 antennae, maxillae, &c, and seems to deposit them in their places, just 

 as the skin of the legs seems to place the legs in position. This, 

 however, is only a true picture to some extent, and there is something 

 vastly stronger in the appendages reaching their true position than 

 a mere submission to being laid down in this way, and, in investigating 

 mouth-parts, &c, and separating them to learn their true connections in 

 freshly moulted pupae, one finds that they go back to their places rapidly. 

 Dropping the pupa into weak spirit will often prevent the appendages 

 falling into their right places, as it distorts them and prevents the 

 chitinous fluid hardening rapidly. Each appendage (leg, wing, 

 antenna, &c.) then appears as a mere watery bag, and looks as if it 

 would take any form at will. The contents are very fluid, and, on 

 puncture, flow out and leave the part (or the whole pupa) flaccid, but 

 it has an envelope of definite form, which it persistently takes when 

 undisturbed and distended by its fluid contents, and this form is such 

 as to place each appendage exactly in its correct position. 



The not infrequent instance of an imago with a larval head, may 

 be due to the head at the pupal moult retaining its larval habit of not 

 breaking up as it should do at this moult, and so maintaining its place, 

 packed with the antennae, &c. Should it succeed in emerging as an 

 imago the larval head will remain. This, however, often prevents the 

 emergence of the imago altogether. The first note on the presence of 

 a larval head on an imago is said to be that by Muller, in Der Xatur- 

 forscJier, for 1781. In the Ent. Mo. Mat/., vii., p. 227, are records of 

 such examples of Pyrameis atalanta, Nymphalis popiili, Gastropacha 

 quern 'folia, and Bombyx mori. We have already recorded (vol. i., 

 p. 428) instances of Anthrocerid imagines retaining the larval head, 

 and Poujade records [Bull. Soc. Ent. France, 5 ser., ii., p. lxxxiii) a 

 pupa of Pieris rapae with the head-parts covered by the head-case of the 

 larva. 



Lovett succeeded (Ent., xiv., p. 176), by placing a pupa of Arctia 

 caia in alcohol, just before it had freed itself from the larval epidermis, 

 in observing that the pupa at this stage has the head, eyes, antennae, 

 legs and wings perfectly free, and the anal orifice quite conspicuous. 



