1909.] NATURAL SCIENCES OF PHILADELPHIA. 557 



pushed it until it touched her she jumped away, and though she soon 

 thereafter felt it once or twice she each time sprang away and remained 

 quiet. I then pushed her gently so that one of her palpi rested on the 

 cocoon; she remained quiet in this position for a quarter of an hour, 

 then suddenly grasped it with her jaws and feet. In this case the 

 maternal instinct did not seem so strong as that of self-protection. 



4. Experiments to Determine Whether Lycosid Spiderlings 

 can Emerge Unaided from the Cocoon. 



It has previously been shown by me (1903, 1, c.) that Lycosid mothers 

 bite open the cocoon along the line of the junction of base and cover, 

 so as to allow the young to emerge. The following observations prove 

 conclusively that the young are unable to bite their own way out of 

 the cocoon : 



Twenty-nine cocoons were removed from as many females of a 

 small Pardosa, found running in a wood, and kept about six weeks on 

 my desk in open bottles out of the direct sunlight. In eleven of these 

 cocoons the young failed to hatch, due either to the handling of the 

 cocoons or to lack of fertilization of the eggs ; while in eighteen the young 

 hatched normally, but failed to emerge, died and shrivelled. In two 

 cocoons taken from females of Lycosa lepida and kept in the same way 

 the young also hatched, but died within the cocoons. 



5. Apparent Mimicry and Stridtjlation in Certain Drassids. 



Geotrecha (Thargalia) bivittata (Keys.), G. pinnata Emerton, and 

 G. crocata (Keys.) are found fairly abundantly during the summer 

 running on the ground in cloudy weather, crocata more in open fields 

 and the others in shaded places in the woods. The first two resemble 

 rather closely in form and movements the macroergates of a large 

 mound-building ant; and the particular locality at which I found 

 bivittata and pinnata most abundant was within twenty feet of such 

 an ant nest,— there being found also many wingless nymphs of the 

 hemipteron Alydus, which also resemble this ant. This seems to 

 constitute a complex case of mimicry. But when these ants are placed 

 together with individuals of Geotrecha they quickly bite and kill the 

 latter, so that the ants are not in any way deceived and there is no 

 myrmecophily. 



In defining the genus Geotrecha Emerton states, in speaking of the 

 abdomen: "It sometimes has a small, hard patch at the front end 

 which is of the same color as the rest of the back and not easily seen." 

 This I have found in all three species mentioned, where it occurs at 



