1903.] NATURAL SCIEXXES OF PHILADELPHIA, 119 



jaws, and sometimes tore at the silken shroud with her jaws. At 6.15 

 she started energetically tearing open the shroud, but all the young 

 did not emerge from this silken envelope until a couple of days had 

 passed. It is difficult to explain this act: did she enshroud the young 

 to protect them from the beetle? Or did she enshroud them mis- 

 taking them temporarily for the beetle? 



Feeding. — It fills one with admiration to watch this feeble spider, 

 with her w^eak jaws and long hair-like legs, overcoming prey much 

 larger and stronger than herself. It is done by enshrouding the victim 

 with great rapidity. In the operation the spider rushes at the victim, 

 then with cephalothorax up and abdomen down applies with her 

 fourth pair of legs, these legs used in very rapid alternate action and 

 sometimes aided by the third pair, a thread issuing from her spinnerets 

 to the victim, and so within a short time renders it immovable. In 

 case web lines interrupt the free action of her legs, she stops her work 

 to bite these lines loose. The act of enshrouding lasts until the victim 

 is nearly hidden by the thread around it, and completely powerless 

 to move, when the spider carries it hooked to her fourth legs up to a 

 higher place in the web and feeds upon it there. The prey is sucked 

 dry, then cut loose from the web. The agility and strength evinced 

 by this spider is marvelous. 



The Shaking Habit. — This is the well-known habit this species has 

 of shaking the body so rapidly by a rotary movement, while in the 

 web, as to render itself almost invisible. Certain Epeirids have the 

 same habit. With Pholcus it is an expression of fear, and is resorted 

 to after the web has been severely jarred. Once a female was seen 

 to shake this way after a male w^as put upon her web ; but I never saw 

 such a case repeated, and believe that the female was shocked by 

 some action on my part. It is never resorted to in order to secure prey. 



Acrosoma gracile Walck. PI. IV, fig. 5. 



This Epeirid, common in many of the local woods, is remarkable for 

 great sexual dimorphism. The abdomen of the female is hard and 

 corneous, angular and prolonged into spines. The male is much 

 smaller than the female and much more rarely found; his small abdo- 

 men is elongated and without spines. On account of these differ- 

 ences it seemed desirable to observe the mating process. 



$No. 322 was captured July 23, and died August 11; she made in 

 her cage only the foundation lines of a web, but no orb, and so was 

 unable to catch the insects given her. c? No. 321 was caught on July 

 23, and died July 28; he also constructed no orb. 



