396 



AMKKICAN SPIDERS AND THEIR SI'INNINOWORK. 



of these were alive within the cocoon, a flossy ball of blackish colored 

 silk different from any I have ever seen. In the centre was a small agglu- 

 tinated mass of white parasitic cells, similar to those above described, to 

 which a number of infertile spider eggs still clung. These cells were 

 probably those of an Ichneumon, Pezomachus dimidiatus Gresson (Plate V., 

 I 1 ig. 5, female, > I), an example of which was found, dead, clinging to the 

 padding o f the spider's egg sac. They had evidently burrowed within 

 the mass of Epeiroid eggs, destroying a number but leaving still many 

 to hatch out. Within these parasitic cocoons, which were all empty of 

 their original occupants, were several Dermestid larvae of various sizes. 

 They were in an intense state of activity, but I did not observe that they 

 preyed upon the living spiders. Besides these I found in the box two 



specimens of a minute Chalcidian, and 

 several living specimens of a small spe- 

 cies of ant, apparently an undescribed 

 Solenopsis. Thus this family consisted 

 of the original spider hosts, their proper 

 F '- SSL KM. 332. parasitic guests Pezomachus, the para- 



FiG.331. cocoons of Pezomachus gracms in a site's parasite Chalcidian. the universal 



Latengrade spider's cocoon. PIG. 332. Spi- n 



der cocoons; one healthy, one infested. destroyer the Dermestid larva?, and that 



inquisitive interloper the ant. It has not 



oeen my fortune to see a more miscellaneous natural combination than this 



Pezomachus does not limit herself to any single group of spiders but 



apparently preys upon all. I succeeded in hatching several, both male and 



Pezo female > of Pezomachus gracilis Cresson (Plate V., Fig. 6, female, 



machus ) fr m cocoons of a Laterigrade spider. Two cocoons found 



sracilis. on the banks of th e Schuylkill, attached to the inner side of the 



bark of a tree, were joined together as at Fig. 332. One of these 



was completely occupied by Ichneumon cocoons. The spider's cocoons are 



3 of very stiff silk, and are covered more or less thickly with minulc 



s of mud. Through this covering Pezomachus had penetrated and 



xlged her eggs upon the spider eggs within. In due time they were 



hatched, devoured the eggs, the shells of which were within. Five pupa 



cases of the parasite occupied the interior. (Fig. 331.) In the adjoining 



ocoon were healthy young spiderlings and a few eggs. 



The cocoon of Epeira apoclisa of England is spun of yellowish silk of 

 a loose texture, about half an inch in diameter, and contains about two 

 English hundred and twent J spherical eggs. From this cocoon, on the 

 Parasites. 1 !th of Jul ^ BkckwaU took both sexes of a small Ichneumon 

 fly, the female of which is apterous, and on another occasion 

 he obtained specimens of the same insect from the cocoon of Epeira um- 

 bratica. J 



1 Spiders Gt. Br. & Ir., page 327. 



