654 



STATE BOARD OF AGRICULTURE. 



are not completely unfurled until about five minutes later. The charac- 



Fig. 7. Developing embryo of poUto leafhopper in midrib of potato leaflet. U 39.) (Photomicroeraphs by Miss E. McDaniel.) 



teristic markings of Empoasca mali do not appear on the young adult 

 simultaneously with the casting of the last nymphal skin, but develop 

 about two days later. The nymphs are active and when disturbed move 

 with a peculiar sidling movement to the other side of the leaf. Both 



Fig. 8. Leafhopper nymphs feeding on under side of potato leaflet. (Natural size.) 



the adults and nymphs feed for the most part on the veins and vein- 

 lets on the undersides of the leaves (Fig. 8) and only occasionally are 

 they found on the upper surfaces. 



LIFE HISTORY STUDIES 



Control measures for insect pests are based upon life history studies 

 of the ipesit in question. From such istudiies the time to combat the 

 trouble most efficiently can be determined. Accordingly observations 



