390 AMKKICAN SPIDERS AND TIIEIK SPINNINOWOKK. 



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 

 I)robably those of an Ichneumon, Pezomachus dimidiatus Cresson (Plate V., 

 Fig. 5, female, X 4), an example of Avhich was found, dead, clinging to the 

 l)adding of 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. M''ithin these parasitic cocoons, which were all empty of 

 their original occupants, were several Dermestid larvis 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 

 FiB, 331. Fig. 332. parasitic guests Pezomachus, the para- 



FiG. 331. Cocoons of Pezomachus gracilis in a sitc's parasite Chalcidiau, the Universal 

 rtro".^reTeaZ:'onei":st?a: '"' ^estroycr the Dermestid larva^ and that 



inquisitive interloper the ant. It has not 



been my fortune to see a more miscellaneous natural combination than this. 



Pezomaclius does not limit herself to any single group of spiders, but 



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



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



Pezo- y 4-) froiyi cocoons of. a Laterigrade spider. Two cocoons found 



eracilis *^" *^''^ banks of the 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 



made of very stiff silk, and are covered more or less thickly with minute 



daubs of mud. Through this covering Pezomachus had penetrated and 



lodged 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 



cocoon 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 

 hundred and twenty spherical eggs. From this cocoon, on the 

 Parasites ■^^*^' °^ J^lj' Blackwall 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. ^ 



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



