THE SHARP-HEADED GRAIN LEAFHOPPER. 7 



Osborn remarks that in Ohio ' ' there are clearly two distinct genera- 

 tions annually." In the Southern States, where there are more 

 generations, these are not so clearly distinct, due to an overlapping 

 of the three stages during the summer months. Because of this 

 overlapping of the egg, nymphal, and adult stages it is very difficult 

 to determine the exact number of generations from field observations. 

 By the use of breeding cages it was possible to determine that there 

 were six distinct generations for southern Arizona during 1914. 

 The cage experiments checked up very closely with field observations. 

 Thus the number of generations may vary from two to six. 



For southern Arizona the first spring generation extended over 

 February, March, and April; the second, over May and the first half 

 of June; the third, over the last half of June and July; the fourth, 

 over August; the fifth, over September; and the sixth, over October 

 and November, the adults of the sixth generation living over winter 

 and ovipositing in February for the following spring generation. 



LENGTH OF EGG STAGE. 



The length of the egg stage in southern Arizona was found to vary 

 from 3 to 35 days, depending upon the temperature, the average 

 being 12 days. Table II gives the length of the egg stage, with the 

 corresponding temperatures, and plainly shows that the length is 

 materiallv shortened during the summer months. 



Table II. 



-Length of the egg stage of the sharp-headed grain leaf hopper, Tempe, 

 Ariz., 1914- 



Number 

 of eggs. 



Date of 



oviposi- 



tion. 



Date of 

 hatching. 



Length of 

 egg stage. 



Average 

 mean 



tempera- 

 ture during 

 egg stage. 



4 

 16 

 6 

 6 

 3 

 5 

 7 

 8 

 10 

 9 

 14 

 20 



Feb. 4 

 Feb. 13 

 Feb. 19 

 Mar. 5 

 Apr. 5 

 May 8 

 May 11 

 ...do 

 June 19 

 July 29 



Aug. 28 



Oct. 1 



Mar. 11 

 ...do 

 Mar. 12 

 Mar. 20 

 Apr. 20 

 May 16 

 May 18 

 May 16 

 June 28 

 Aug. 1 

 Sept. 2 

 Oct. 5 



Days. 

 35 

 26 

 21 

 15 

 15 

 8 

 7 

 5 

 9 

 3 

 15 

 4 



"F. 



59.0 

 61.7 

 67.4 

 65. 9 

 70.4 

 74.3 

 74.3 

 74.1 

 85.0 

 93.0 

 82.8 

 71.0 



Av 



erage 



12.75 



.Si mm ,\ UY, SlfOWIXi; CONDENSED AVERAGES. 



When 



The aver- 



lengl ii "i 



11 man 



egg tage 



tempera- 



averai 



ture was— 



l)n 11 



•F. 





62. 7 



15. 



68.1 



8.0 



77. H 



1 ■ 



80. 2 



