396 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



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., 

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

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

 tlie 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 larvaj of various sizes. 

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

 preyed ui)on 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 jjroper 

 Fic. 331. Fig. 332T parasitic guests Pezomachus, the para- 



FiG. 331. cocoon.s of Pezomachus graciii-s in a sitc's parasite Chalcidiau, the Universal 



Laterigrade spider's cocoon. Fn:. 332. Spi- i. i.-LT\ i*ii jj.ii 



der cocoons; one healthy, one infested. dcstroyer the Demiestid larva>, and that 



inquisitive interloper the ant. It has not 



been 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 



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

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



gracilis *^" *^^^ 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 le.ss 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 

 Parasit ^^^^'^ o^ July, Blackwall took both sexes of a small Ichneumon 



fl}', 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. 



