ENEMIES AND THEIR INFLUENCE. 



395 



Double 

 Parasit 

 ism. 



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

 City (luring winter (1883), and opened Juno 6tli 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.' 



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 escai)ed 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 CoiDhinaria 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 Orbweaver's young along with various "squatter sovereigns" of the 

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

 cisco (August, 1883), a specimen of Epei'ra 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 copliinaria, 

 opened to show tlie pupa cases of a brood 

 of parasitic Ichneumon flies. 



Treble 

 Parasit- 

 ism. 



' Prof. Wilder has observed the same fact. Proceeding.s American Association Adv. 

 Science, 1873, page 258. 



