MOULTING HABITS OF SPIDERS. 95 



Orb weavers moult as follows :^ Preparatory to casting its skin the 

 spider spins several strong lines in the vicinity of its snare, from wliich 

 it suspends itself by the feet and a thread held in the spinners. After 

 remaining for a short time in this situation the covering of the ceph- 

 alothorax gives way laterally, disuniting immediately above the insertion 

 of the falces and legs, so that the head and thorax are the first parts 

 liberated. 



The line of separation pursues the same direction, passing midway 

 through the pedicle until it extends to the abdomen, which is next disen- 

 gaged. As the thread held by the spinnerets is usually shorter 

 Orbweav- |]-,j^j^ the legs and undergoes little alteration in length, the ab- 

 ^ ^ ... domen is gradually deflected from its horizontal to a vertical 

 ' position, nearly at right angles with the cephalothorax. By this 

 change, attended with numerous contortions or undulatory movements of 

 the body, the spider frees the abdomen, which falls back in a wrinkled 

 saclike mass united to the dorsum of the cephalothorax by the upper half 

 of the tegument of the pedicle. 



The legs are the last and most difficult to detach, but are drawn out 

 downward and usually entire by successive muscular contractions and 

 strains, with brief intervals of rest. Blackwall thinks that the spines with 

 which the legs are provided facilitate the oj^eration ; for, as they are di- 

 rected down the limbs and are movable at the will of the animal, when 

 it has partially withdrawn the legs from their sheaths by contracting 

 them, it can prevent them from reentering by slightly erecting the spines 

 and thus bringing their extremities in contact with the inner surface of 

 the integument. As the spines also and simultaneously with the legs 

 undergo moulting, it may be doubted if their service in this respect is 

 very great. 



When the spider has completely disengaged itself from the sheath it 

 remains for a short period relaxed and exhausted, suspended solely by a 

 thread from the spinnerets. The entire process, as above de- 

 M^^lt scribed, may be completed in about twenty minutes under normal 

 conditions, but varies in length of time according to circumstan- 

 ces. After a short rest the spider adjusts its position, making itself more 

 secure upon the suspensory lines by seizing them with the feet; stretches 

 its legs, bends and unbends them, passes them through the mouth, and 

 hangs in repose until its strength is sufficiently restored and its limbs have 

 acquired the requisite firmness, when it ascends its filaments and seeks 

 its nest or retreat, or takes position upon its snare.^ 



1 This detailed description is that of an Epeiroid, and is made from my own observa- 

 tions combined with those of Blackwall, Wagner, and others. 



^ Blackwall, Researches in Zoology, pages 306, 307 ; British Spiders, Introduction, page 7 ; 

 Id., Ann. and Mag. Nat. Hist., XV., 1845, page 230 ; Id., Trans. Linn. Soc, XVI., pages 

 482-484 ; AVagner, La Mue des Araign(^es, page 284. 



