His 



THE AMERICAN NATURALIST [Vol. XLIV 



fore-legs and palpi just as in normal courtship. Two 

 males, a smaller and a larger, of Phidippus purpuratus 

 were placed together; the larger was aggressive, the 

 smaller exhibited towards him normal courtship motions. 

 In neither of these cases were females present. Two 

 males of the brilliant Phidippus mccookii Peck, on being 

 placed in one cage, on several different occasions, raised 

 the legs, side-wheeled, and flexed the abdomen laterally, 

 resembling a courtship ; I had no female of this species 

 to determine the normal courtship, but to females of 

 P. clarus Koch they acted in the same way. Two males 

 of Zygoballus bettini Peck, were placed in a cage and 

 watched each other attentively, but without courtship; 

 an immature female was introduced, when each male pro- 

 ceeded to court her: advancing and retreating by short 

 quick steps, the first legs raised vertically and parallel 

 and these and the palpi twitching; the female ran away 

 from both, and after I had removed her the males ex- 

 hibited the same movements towards each other, with the 

 only difference that the raised legs were somewhat di- 

 vergent and that the smaller male fled when the larger 

 came too near. Evidently in these cases the males mis- 

 took one another for females, which would indicate that 

 their visual discrimination is far from precise— perhaps 

 less than that of the females. 



The female is also actuated by sexual desire, sometimes 

 quite as strongly as the male; this is the case with Therid- 

 ium tepidariorum, where the female seems insatiable, and 

 the Peckhams (1889) observed a female of Saitis pulex 

 approaching a male with courting movements. In ther- 

 idiids and epeirids the female signals along the snare 

 lines quite as vigorously as the male does. 



But whenever she is larger than the male, sho exhibits 

 as a rule, no great fear of him. She may express her 

 desire to the male by remaining quiet and passive, or 

 by touching him gently or moving towards him, or by 

 counter-signalling by means of lines of her snare; and 

 sometimes she may take the initiative in this. Where 



