390 AMERICAN SPIDERS AND THEIR SPINNING WOK K. 



found eating the same Theridium that had devoured her predecessor. 

 Such observations indicate a marked hostility existing hetween these two 

 powerful examples of their family a sort of aranead feud. 



Professor Hentz sometimes enclosed specimens of these spider eaters 

 with other araneads in a glass jar, in order to watch their motions. The 

 moment another spider was thrown in, Interfector showed by its 

 Du'elfT attitude that it was conscious of the presence of an enemy. For 

 a moment it moved its first and second pairs of legs up and 

 down, and then slowly approached its victim, and generally killed it. A 

 Theridium tepidariorum thrown into the jar manifested great terror, but 

 in a little while, or, as Professor Hentz puts it, "after some seeming reflec- 

 tions upon fortitude and necessity," it prepared for the mortal combat, and 

 cautiously advanced towards the Mimetus, which began to move more 

 slowly. Theridium, when near her adversary, threw out a long thread on 

 which were several globules of transparent fluid. This partially succeeded, 

 for Mimetus was caught by one leg, and while Theridium retreated for ob- 

 servation it was dragged about for a long time before it succeeded in free- 

 ing itself. The battle presently was renewed, and this time Theridium was 

 conquered and eaten. 1 



From these interesting observations it appears that this formidable spe- 

 cies of Theridium is a favorite object of attack with Mimetus. It is one 

 of the most powerful and ferocious of its kind, being able to overcome and 

 destroy the largest insects, and, as we have shown (Vol. I., Chapter XIII.), 

 even to entrap and destroy a small snake and a half grown mouse. The 

 courage, ferocity, and combative skill of the adversary which is able suc- 

 cessfully to meet and vanquish it are thus at once manifest. I have 

 found Mimetus interfector parasitic upon the snares of other spiders in 

 the neighborhood of Philadelphia, but have never witnessed an actual at- 

 tack by her. On one occasion I found her ensconced upon the snare of 

 an Orbweaver, having evidently destroyed the occupant. 



Mimetus syllepsicus, according to Hentz, 2 has the same piratical habit 

 as her congener Interfector. This spider was found in the tent of Epeira 

 labyrinthea, which it had no doubt killed. The webs and cocoons of its 

 victim were untouched, and the squatter seemed perfectly at home in its 

 new domicile. It strikes one as a remarkable development of instinct 

 which has formed within a tribe and families having fixed sedentary 

 habits a disposition to leave the snare and go, like the Wandering groups, 

 to seek prey, and especially to raid the nests of fellow araneads therefor. 



But it may be noted that the piratical destroyer confines its raids 

 Origin of , , ,. , , r 



the Habit s P ecie s whose nesting habits, m whole or in part, are sim- 

 ilar ^ to its own. That is to say, Mimetus finds its best pre- 

 serves and hunting grounds upon the netted cross lines of Theridium and 



1 Spiders of the U. S., page 138. 2 Spid. U. S., page 140. 



