ei 
a Se ie f-, P ~~ = —_ 
MOULTING HABITS OF SPIDERS. 101 
conditions. Blackwall had already noticed that food and temperature 
exercise a decided influence,! and Wagner has confirmed the fact. Moult- 
ing is suspended in winter in natural site; but if spiders be housed in 
warm rooms the moult may be artificially stimulated, but the 
Modify- moulting intervals are then longer than usual in natural condi- 
ved tion. If a young brood of the same age be exposed to different 
gents. ; ‘ : 
degrees of heat they will shed their skins at intervals corre- 
sponding thereto, the warmer ones earlier, the colder later. The lack of 
sufficient nourishment retards the moulting epoch, and tends to make the 
act more difficult and dangerous, so that many spiders die in or after the 
act from inanition. 
Causes affecting the normal health of the organism modify the moult. 
Blackwall discovered that young spiders infested by the larva of Poly- 
sphincta carbonaria, an insect belonging to the Ichneumonide 
which feeds upon their fluids, never moult.2 Wagner notes the 
effect of the prick of a Pompilus sting upon two male Trochosas ; 
one stung July 8th remained sick and languid until August 7th, an unus- 
ually long period, and then moulted. During the act, probably for lack of 
vigor, the legs were contorted and deprived of motion. Another male, 
stung at the same time, passed an interval of a month and ten days before 
moulting, a great retardation as compared with subjects of his own age 
who had long before that shed their skins. This spider began moulting 
August 17th, and on September 2d, when it was moribund, it had only 
achieved the moult of the abdomen and corselet. The legs were with- 
drawn from the old skin in the morning and appeared to be normal, but 
in the evening they were bent up and flattened, doubtless the result of 
imperfect alimentation during the two months succeeding the sting, and of 
the imperfection of the interior moult. 
Neither of these wounded spiders made any preparation for moulting 
by stretching supporting frames of silk lines. The normal conduct and 
periodicity of moulting appears thus to depend upon three kinds of agents: 
first, the interior conditions of the animal’s development; second, the expen- 
diture of the reserve for the maintenance of internal heat and locomotion ; 
and, third, external conditions, such as heat and food.* 
Pompilus 
Sting. 
VI. 
After moulting, all spiders, old as well as young, are in a state of 
greater or less feebleness, proportionate to the difficulty and length of the 
act. They hang in a relaxed and helpless condition upon their proper 
snares, if sedentary, or upon temporary scaffolds woven as supports; one 
1 Zoological Researches, page 309. 
2 Brit. Assn. Advanct. Sci., 14th meeting, pages 70, 71. 
> Wagner, La Mue, page 357, 
