394 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



adianta, a si)ecies of Orbweaver. The parasite was two millimetres long, 

 a yellowish green color, and smooth, except slight warts upon the back. 

 At first the spider seemed to feel little inconvenience from its guest, but 

 on the fourth d ly it sat motionless, and on the fifth it had been de- 

 voured, only a small bit of skin remaining, while the caterpillar lay 

 curled up in a half circle, grown to twelve millimetres in length and two 

 millimetres in width across the middle of the body. Subsequently it made 

 a cocoon on the heath, but developed no further. None of the above 

 larvaj moulted, which, according to Menge, is characteristic of parasites 

 within the body, a habit that shows quite as striking adaptation as does 

 freedom from moulting in an infested spider. 



One of the most common superstitions heard among persons unin- 

 formed in natural history, is that a horse hair, when placed in the water 

 under certain conditions, will turn into a snake. I have heard 

 this fact averred by eye witnesses, who believed confidently that 

 they had seen the hair' suddenly come to life and wiggle off through the 

 water, ^his astonishing statement is explained by that 

 most interesting and least enjoyable of natural facts, 

 parasitism. Crickets, grasshoppers, and spiders are 

 known to be the hosts of a species of our common 

 Gordius, the same probably as that described a num- 

 ber of years ago by Prof. Joseph Leidy as Gordius 



Fig. 328. Fig. 329. ."',_,'' ,. . ^ ,."'_, 



Parasitic Gordius (Fig. 328) aquaticus.^ From this emuient naturalist I have re- 



infesting Lycoaa scutu- ccivcd a Specimen of Lycosa scutulata, from which a 



Gordius was taken. I have figured the spider just as 



I received it, it being very much damaged when it came to my hand ; 



the parasite is also drawn, both figures natural size. (Figs. 328 and 329.) 



VII. 



We have thus far considered the foes which assail the life of the 

 spider after it has escaped from the cocoon. This does not complete the 



doleful record. Her cradle life is beset by even more formida- 

 _ ble perils. The maternal instinct which, in the spider mother, 



prompts to cunning protection of her eggs in admirably wrought 

 cocoons, inspires the Ichneumon fly to penetrate the silken bars and wards, 

 and place the eggs of her parasitic young upon the spider's eggs. Our 

 knowledge of the parasitic Hymenoptera pi-eying upon cocoons of spiders 

 has j'et to be much enlarged, but we know that the genus Pezomachus is 

 one of the most persistent guests, and that she carries vast ravages into 

 the aranead ranks. A few notes will be given, culled from many observa- 

 tions upon the destructive habits of this genus. 



Proceed. Acad. Nat. Sci., 1850-51, page 98. 



