— cer eee ee ee 
a “4 , 
100 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
in fact the vitelline membrane, and deliverance therefrom constitutes the 
first moult. : 
The number of times that spiders change their skin before they be- 
come adult is not uniformly the same as regards every species, not even 
perhaps the same within the individuals of any one species. 
Periodic- For example, Blackwall made some careful observations upon the 
a 3 frequency of moulting in a young female of Zilla x-notata! and 
oulting. : : ; : : 
Epeira diademata, which I arrange for sake of comparison in 
the following tabulated form :— 
ZILA X=NOTATA. EpPerma DIADEMATA, 
Days Interval. Days Interval. 
Disengaged fromegg. ..... Mareh 30th, April 14th, 
1. Moulted in cocoon. ...... April 8th, 9 April 24th, 10 
Quitted ‘cocoon. 7. Ss 2 May Ist, May 3d, 
22 Moulted).co5 0. dit Re June 4th, 542 
85; Momltiad 5. Sink ond BP nce ata June 22d, 18 June 21st, 50? 
Cee covullityal SU sense eee eles its tes July 12th, 20 July 10th, 19 
Gs Moulted sir. ches: Teh ameter on August 4th, 23 August 3d, 24 
There were five moults in each case; the intervals between disengage- 
ment from the egg and the first moult were about the same; the Epeira 
remained much longer in the cocoon than the Zilla, perhaps for some local 
reason; its next moult, the first after emerging, was not recordeq But 
there was evidently an irregularity during the interval from moult 1 to 
moult 3 where the record can again be compared. However, if we take 
up the comparison from the dates of leaving the cocoons, the moulting 
intervals of the two species are of nearly equal length. Perhaps this table 
represents fairly enough the normal periodicity of moulting with Orb- 
weavers. 
With Lycosids (Trochosa), according to Wagner, the second skin is 
rejected in about six days, at a time when the younglings dwell in part 
within the cocoon and partly on the mother’s back. The third 
moulting occurs six to seven days thereafter upon the mother’s 
body. The fourth moult occurs seven to eight days after the 
third, partly on the mother’s body and partly in the maternal burrow. 
After this moult the younglings leave the burrow and begin independent 
life. At this time the spiderlings have attained more than one-tenth their 
normal size, and have before them a series of moults amounting to ten in 
all. The time required for full development and for completion of all the 
moults is from one hundred and sixty to one hundred and _ ninety-five 
days, excluding winter months. 
The periodicity and the safety of moulting are modified by various 
Lycosids. 
Trochosa. 
1 Epeira calophylla Blackw. 
* There is probably a break here in the observation, and a loss of several moults, 
* Wagner, Note on the Tarentula, Comtes rendus de la Sect. Zool. de la Soc. Imp. des 
Se. Nat. de Moscow, 1866. 
