1879.] 223 



at a right angle to tlie others. The head continues to droop, and by 

 this it is made certain that the final change approaches. Presently 

 there is a twitching of the spines, first confined to one segment, but 

 extending soon over the whole body, and changing into a waving 

 motion. This is accompanied by a twisting of the segments beneath 

 the skin, which increases in strength and continues some minutes. 

 Two or three times a spasm of contraction comes on, by which the 

 body is lifted up into the last one or two segments and let fall again. 

 Then a creeping movement under the skin commences, extending from 

 the posterior segments forward, and seems to break the skin loose 

 from the body, and one wave after another runs along till the dis- 

 tended skin on the anterior segments bursts. V This always takes place 

 on the middle of the dorsum, on the 3rd segment, and the mesonotum 

 of the chrysalis is forced through, splitting the skin up to the head 

 (or first segment), and sometimes splitting the skin of the head also. 

 By the continued creeping movement, the body is slowly forced through 

 the rent. As this is oblique, the ventral side of the chrysalis is fully 

 three segments behind the dorsal in the divesting, the skin on the 

 anterior segments fitting tight as a glove, although it is loosening and 

 packing in a mass about the anal feet. - In about ninety seconds from 

 the time of the rupture the skin on the dorsal side has been pushed 

 back to 10, and the effort begins for the extrication, of the tail of the 

 chrysalis from the caterpillar skin. This tail must be withdrawn and 

 fastened outside the skin to the same button of silk which the cater- 

 pillar clung to. At this instant the skin covers the ventral side of 

 the chrysalis to 8th segment, but is moving up constantly, and as the 

 chrysalis bends the posterior half of the abdomen sharjjly back to force 

 the tail out of the sheath, the segments are pinched together and there 

 is at the same time a pinching in of the skin. But there is no seizing 

 of the outside of the skin ; if there w'ere no other reason, the spines 

 would make this impossible. The tail now free, the chrysalis straightens 

 itself up, and swinging on the ligament, lifts itself towards the silk, 

 the last segment describing an arc of a circle of which the ligament is 

 the radius, and the tail, which at the same instant is curved forward, 

 is brought round and over the considerable packet of the old skin and 

 with precision strikes the silk. An observer, knowing nothing of the 

 ligament, seeing only the violent contortions, the abdominal segments 

 expanding and contracting to the utmost, while at the same time the 

 chrysalis steadily rises toward the silk, naturally concludes that the 

 one movement is the direct result of the other. When I lifted the 

 flap of skin entirely clear of the struggling segments and cut it off a 



