ENEMIES AND THEIR INFLUENCE. 



395 



The outer case of a cocoon of Argiope cophinaria was taken at Atlantic 



City during winter (1883), and opened June 6th following. It was then 



pierced with several round holes. The lower part of the flask 



was occupied by a number of white cocoons of a parasitic hy- 



menopterous insect. They were each three-eighths of an inch 



long, were grouped in a bowl shaped mass quite around the 



bottom of the egg sac, and were covered with a delicate white silken floss. 



Many of them were pierced at one end with a hole corresponding with 



the one on the outside of the spider's cocoon. (Fig. 330.) From these 



holes the insects, probably a species of Pezomachus, had made their escape, 



leaving their mahogany colored shells within their white pupa cases. Some 



of the Ichneumonid cocoons were without the single large opening, but 



had minute punctures not much larger 



than pin holes. These were doubtless the 



exit holes of a species of Chalcidian. 1 



Thus the larvae of the parasitic Ich- 

 neumons were themselves preyed upon by 

 a parasite. However, in each case some 

 individuals of the original host escaped the 

 parasitic destroyer. The Chalcidians did 

 not destroy all the Ichneumons, as the exit 

 holes attested ; and, notwithstanding the 

 entire lower part of the spider's egg sac 

 was occupied by the hymenopterous en- 

 campment, whose white tents pushed up 

 against the brown wadding spun by the 

 mother spider, a large number of young 

 spiderlings occupied the field. They were 

 active and apparently healthy, scrambling 

 among the woolly fibres of their home 

 quite down to the cocoons of their invaders. 

 Whatever ravages the Ichneumons may have made among the spiderlings, 

 there were certainly enough of them still left. I have found other cocoons 

 of Cophinaria similarly occupied with some of the perfect Chalcids entan- 

 gled in the spider silk. 



These are not the only examples of peaceful occupation of a cocoon 

 by the Orb weaver's young along with various " squatter sovereigns " of the 

 parasitic tribes. I received from Mrs. Eigenmann, San Fran- 

 cisco (August, 1883), a specimen of Epeira accompanied by what 

 was supposed to be, and probably is, the cocoon. The adult 

 spider, a female, is black, with faint dorsal foliated marks, and 

 the young are beautifully marked with black and white. A large number 



FIG. 330. Cocoon of Argiope cophinaria, 

 opened to show the pupa cases of a brood 

 of parasitic Ichneumon flies. 



Treble 

 Parasit- 

 ism. 



1 Prof. Wilder has observed the same fact. Proceedings American Association Adv. 

 Science, 1873, page 258. 



