. American spiders and their spinning work. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits. Spiders. MOULTING HABITS OF SPIDERS. 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
. American spiders and their spinning work. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits. Spiders. MOULTING HABITS OF SPIDERS. 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 Moult 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 It will be seen from the cut that the abdomen has been withdrawn from the old tegument forward through the cir- cular rent at the base, where it was united to the pedicle. Even the long spinnerets retain their hab- itual position curled upward along the apex. The ab- dominal skin of this spi- der is So much thicker than that of ordinary araneads, and withal is so heavily cov- 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 F,r" ^ A cast skin of Mygale'showing 8Ught rupture of parts' 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 with
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectspiders, bookyear1889
