162 
Psyche 
[June-August 
SOME LIFE HISTORY NOTES ON THE BLACK WIDOW 
SPIDER LATRODECTUS MACTANSa 
By Phil Rau. 
St. Louis, Mo. 
This spider in livery of shining black decorated with bright 
red blotches, and called by Comstock the black widow spider, 
is often found in the vicinity of St. Louis under rocks and debris 
in sunny pastures. One specimen, with its round, white egg-case, 
was taken from her web high up in a corner of a barn on June 
23, 1922. 
In captivity she made four more of these egg-cases, on June 
24, July 12, August 4 and August 15 respectively. After the 
making of each, her abdomen was shrunken to about half its 
former size, but it soon returned to normal proportions. Despite 
the fact that this individual had not access to the male, after its 
capture, the eggs in all five cocoons were fertile; this circum- 
stance shows that it is not necessary for mating to precede each 
case of oviposition. 
All the young in each cocoon emerged from one hole the 
size of a pin-head, probably made by the first restless spiderling 
The emerging young of two cocoons were counted; one gave 
forth 101, and the other 92 spiderlings. The young at emerging 
do not resemble the mother, whose color is black and red, but 
they are all of a medium shade of brown. While the young do 
not spin nests of any certain form, they do spin webs of criss- 
cross threads to which they cling. Fig. 1 shows a young spider 
(enlarged four times) clinging to these strands. In the glass 
cage in which they were kept, they almost always rested with 
the ventral surface of the body upwards, and with four or more 
legs holding onto the strands of criss-cross silk, as figured above. 
While one seldom sees a nest of definite contour when one 
finds these adult spiders under stones, here confined in a large 
glass box (an unused aquarium), this spider made a large hollow 
^Identified by Mr. J. H. Emerton. 
