1914.] NATURAL SCIENCES OF PHILADELPHIA. 181 



Apr. 17, 1909 1 9 July 30, 1910 . 1 d" 



Sept. 21, 1909 Id" Oct. 5,1910 4 d^* 



Sept. 30, 1909 1 9 Oct. 7, 1910 3 d^ 1 9 



Oct. 27, 1909 1 cf Apr. 11, 1911 1 9 



1 d Apr. 15, 1911 1 d 



1 d 1 9 Apr. 22, 1911 2d 



1 d Sept. 5, 1911 1 9 



1 9 Sept. 11, 1911 1 9 



1 d Sept. 21, 1911 1 d 



1 d Sept. 24, 1911 • 1 d 



1 d Oct. 4, 1911 1 d 



The existence of two broods, one emerging l>etween the end of 

 March and the end of April, the other in September and October, 

 are clearly shown. The two specimens in June and July, respectively, 

 were probably representatives of a third brood. 



The model, Danaida strigosa, appears to be much rarer than its 

 mimic at Phoenix — at any rate, in the localities where Dr. Kunze 

 collected. From this place I have only received 2 males, captured 

 July 2 and 6, 1912; from Tucson — 1 female May 26, 1 male June 7, 

 1 female June 9, 1 male August 19, all in 1896; from Prescott (5,400 

 feet), in western Arizona — 2 males and 1 female July 15, 1912. 



Dr. R. E. Kunze, of Phoenix, Arizona, who has hftd a long and 

 intimate experience of the butterfly fauna of the State, kindly informs 

 me that, in the Phoenix (1,100 feet) and Tucson (2,400 feet) districts 

 and between them, L. obsoleta is almost exclusively found in the 

 valleys, along the river-bottoms, and by the canals, where its larval 

 food-plant, a willow, grows.^ It is commoner in the river-bottoms, 

 especially near the streams, than by the canals. Danaida strigosa 

 flies with it in these situations and is indeed commoner there than 

 elsewhere, but, unlike the mimic, it is also found in other places. 

 It is impossible to state the relative proportions of Danaine and 

 Limenitis, but by the rivers and canals the mimic is the commoner 

 in the ratio of about twelve or fifteen to one. The proportion^ at 

 Tucson and Phoenix seem to be the same. 



Danaida plexippus occurs, but is scarce in the Salt River valley at 

 Phoenix. Dr. Kunze estimates that it may exist in the ratio of one 

 to fifteen of D. strigosa, but in some seasons he does not meet with 



2 The armatures of two of these males were studied by Dr. Eltringham (p. 190) 

 ' Dr. Kunze adds in his letter of August 5, 1913: "I should say that obsoleta 

 has here [Phoenix] from 3-i broods in a season, from April 1st up to November 

 1st, in a mild autumn, of course. I think the last brood oviposits on cotton- 

 wood, our Populua fremonti and other species, because its leaves keep green till 

 latter part of December, whereas willow drops leaves earlier." 



