OF WASHINGTON. . 43 



EXPLANATION OF PLATE I. 



Fig. I. Astraptor illuminator. (After Murray.) 



a, head and prothorax from below. 



b, head from above. 



c, head from below. 



d, leg. 



2. Astraptor sp., from Guatemala. (Original.) 

 a, head. 



— Professor Webster spoke on the spring grain-aphis {Tox- 

 optera graminum Rond.) and the very great importance of 

 the pest in the Middle West. This insect is probably a native 

 of Europe and was introduced a number of years ago; he had 

 himself worked on its life history, in 1884, in Northern Indi- 

 ana. This insect has been found over a considerable area in the 

 United States from latitude 41° south and in altitudes varying 

 from 19 feet to 5000 feet above sea level. Weather conditions 

 during winter and spring almost entirely control the destruc- 

 tive numbers of many pests, but in this case unfavorable 

 weather seems to aid the multiplication of the pest. The Tox- 

 optera will breed through the entire winter where the tempera- 

 ture is occasionally below the freezing point, while during this 

 period the parasites are entirely dormant. It takes but a few 

 warm sunshiny days for the parasites to appear and begin 

 their telling work, multiplying enormously. It is a peculiar 

 phenomenon that the Toxoptera should breed so prolifically in 

 cold climates when it is a decided warm-climate species. Fre- 

 quently the parasitized Toxoptera are so numerous that the 

 entire field assumes a brownish color, since the parasites pro- 

 duce a brownish leathery appearance in the later stages. 



Professor Quaintance reported that the black peach-aphis 

 {Aphis persicce-niger Er. Sm.) bred throughout the winter on 

 peach trees in the insectary yard of the U. S. Department of 

 Agriculture, although at times the trees were covered with 

 sleet and ice. He spoke of his observations on the eggs of 

 Aphis mali Fab., in which he found that less than 2 per cent 

 of the many eggs laid preserved their form through the winter 

 and were evidently fertile. Apparently over 98 per cent were 

 infertile of the 2.000 or more examined. 



