MOULTING HABITS OF SPIDERS. 99 
herself upon the third pair in unsheathing the fourth, upon the second to 
free the third, and so on. 
The abdomen does not commence to moult until after the cephalothorax. 
It is disengaged from the skin, without the aid of the legs, by means of 
contractions of the abdominal muscles, which produce undulatory move- 
ments of the skin in the direction from the cephalothorax toward the 
spinnerets. The cast skin of the abdomen is always much wrinkled, owing 
to its extreme softness and fineness, that permits it to fold up under 
pressure. In this saclike abdominal moult one finds the moulted lungs and 
glands, and fragments of the moult of the intestine and muscles. (Wagner.) 
The skin of Mygale when cast is sometimes so little broken, as shown 
by Fig. 63, that by placing the corselet shell upon the sternum and pasting 
it down to the falces, a casual observer might think it a living 
lat a creature. It will be seen from the cut that the abdomen has 
been withdrawn from the old tegument forward through the cir- 
cular rent at the base, where it was united to the ee Even the long 
spinnerets retain their hab- ~ 
itual position curled upward 
along the apex. The ab- 
dominal skin of this spi- 
der is $0 much thicker than 
that of ordinary araneads, 
and withal is so heavily coy- 
ered with strong hairs, that 
it more readily retains its 
usual form, instead of 
shrinking up in a wrinkled 
mass, as with most species. 
Sometimes, however, the cast 
is not so complete as here shown. In this figure the line of rupture 
along the sides of the cephalothorax is well shown; also the usual mode 
in which the pedicle is parted, uniting the abdomen on the one hand and 
the corselet on the other to the sternum, The mandibles have evidently 
been withdrawn backward by a motion the reverse of the abdomen, as 
shown by the unbroken moult fallen forward upon the moult of the mouth 
parts which adhere to the sternum. 
Fic, 63. A cast skin of Mygale, showing slight rupture of parts. 
V. 
Some spiders issue from the eggs with their feet free; others, as 
Epeiroids and Theridioids, come out having their feet adhering under the 
abdomen. They remain thus for six days, more or less, when they cast the 
first tegument and quit the cocoon.!| The skin thus enclosing the legs is 
‘Simon, Histoire Naturelle des Araignées. 
