June, '11] SEVERINS ON WALKING-STICK 31.? 



lowed then by the rest of the thorax, and finally by the abdomen 

 (Fig. 7). Of the appendages, the middle legs are liberated first, then 

 the antennse, followed by the front and finally by the hind legs. One 

 can easily observe the body and legs gradually withdrawing as the old 

 skin becomes empty (Fig. 7, e). 



A molting specimen examined under a binocular microscope, 

 shows that a peristaltic-like movement passes from the posterior end 

 of the abdomen forward at intervals. With each series of these move- 

 ments the body is withdrawn a short distance out of the old skin, 

 the legs assisting in this process of extraction from the old integument. 

 At each attempt to withdraw the legs from the old exoskeleton, such 

 an energetic pull is exerted upon the limbs, that each coxa presses 

 against the body and forms there a temporary indentation. 



After the walking-stick has withdrawn its appendages, it appears 

 to be exhausted by the tedious task of ecdysis. It frequently happens 

 that the entire body is not completely withdrawn from the cast skin, 

 and in such instances the insect may remain suspended by the tip 

 of the abdomen within the exuviated integument for half an hour 

 or longer. In this position the head hangs downward, the legs are 

 sprawled out and the antennse are held forward parallel to the long 

 axis of the body. This attitude does not have any resemblance to 

 the characteristic resting posture which the walking-stick assumes 

 during the day-time; but in all probability it allows the newly ex- 

 posed integument to harden and prevents any malformations from 

 developing. 



The body of the walking-stick, as well as the legs and antennae, 

 may assume all sorts of abnormal shapes when the insect is unable 

 to extricate itself entirely from the exoskeleton. If, in the process 

 of molting, a specimen falls from the leaf or branch to which it was 

 clinging to the bottom of the breeding cage, many malformations 

 may result, especially if the insect experiences difficulty in withdraw- 

 ing from the old skin. If any leg should happen to be caught in the 

 exuvium, that leg is usually thrown off. We have observed one 

 male individual throw off all of its legs during the last molt and even 

 then it was unable to free itself entirely (Fig. 8). After the newly 

 exposed integument of this specimen hardened, the body assumed an 

 S shape (Fig. 8). It may be possible, that whenever difficulty of this 

 nature occurs during the process of molting that the exuvial or molt- 

 ing fluid which lubricates the two skins at the time of ecdysis, hardens 

 and prevents the parts from being extricated. In all probability 

 autotomy among the Phasmidae owes its origin to the difficulty expe- 

 rienced in withdrawing the appendages during the process of ecdysis.. 



An exuvium immediately after being shed, may be stretched out. 



