396 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Fig. 331. Fig. 332. 



Fig. 331. Cocoons of Pezomachua gracilis in a 

 Laterigrrade spider's cocoon. Fig. 332. Spi- 

 der cocoons ; one health.v, one infested. 



of these were alive within the .cocoon, a flossy ball of l)lackish colored 

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

 tinated mass of white itarasitic 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 Cressou (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 

 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 larvee of various sizes. 

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

 preyed u}>on the living spiders. Besides these I found in the box two 



specimens of a minute Chalcidian, and 

 several living specimens of a .small sjie- 

 cies of ant, apparently an undescribed 

 Solenopsis. Thus this family consi.sted 

 of the original s})ider hosts, their proper 

 parasitic guests Pezomachus, the para- 

 site's parasite Chalcidian, the universal 

 destroyer the Dermestid 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, 

 *X 4) from cocoons of a Laterigrade spider. Two cocoons found 

 on the banks of the Scliuylkill, attached to the inner side of the 

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

 was comj)lctely occupied by Ichneumon cocoons. The si)ider'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 



_ ., 18th of July, Blackwall took both sexes of a small Ichneumon 

 Parasites. „ i ,. i 



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. ^ 



Pezo- 

 machus 

 gracilis. 



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



