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Show 1937] Table 6. 131 Knowlton> Control of the Beet Leafhopper in Utah Estimate of Euiettis tenellus average consumption, per acre, for the period 1930-1933. This assumes an average of 400 Uta stansburiana stansburuma per acre. Average No. Estimated No. Lizards E. tenellus per stomach E. tenellus eaten per months March 15* 400 1.00* 6,000 April 25* 400 1.00* 10,000 May 31 400 0.17 2,108 June 30 400 0.00 0,000 July 31 400 0.80 7,920 August 31 400 2.37 29,388 September 30 400 2.07 25,688 October 31 400 15.00 168,000 400 3.82 15,280 Days pro Month November 10* 3,600 Total for year Lizard days 264,364 the highway west of Delle. This long, narrow strip attracted large numbers of lizards from the nearby shadscale, throughout the season. An estimate of four hundred lizards to the acre, at this place, seems to be conservative. As suming this number of lizards to be present, using the average number of ienellus per stomach for the months when calculations were made, and calcu lating the average number per month for March, April, and November as shown by Knowlton and Janes (20) it may be roughly figured that the aver age control per acre upon this area was 264,364 beet leafhoppers per year. Allowing for the rapid digestion which occurs (29) this figure probably should be 25 to 50 per cent higher. A microscopic examination was made of the contents of 4021 Uta S. stansburiana stomachs, 2249 of them being found to contain beet leafhoppers totaling 5,390 adult and 10,576 nymphs, or a total of 15,966 E. tenellus (Tables 7-8). Knowlton (29) reported that 78 per cent of the beet leafhopper nymphs digested beyond recognition in 6 hours, none being recognizable beyond 18 hours; 80 per cent of the adult leafhoppers were digested beyond recogni tion in 12 hours. Thus lizard stomachs collected throughout the day would contain in recognizable condition less than a normal days tenellus consumption. Table 9 records thirty-three localities from which lizards containing tenellus were collected, the largest numbers of lizards being taken at Dolomite, Iosepa, and Timpie, in Tooele County, where this small lizard occurs in abundance upon the beet leafhopper breeding grounds. Table 10 records the total number of utas collected each month, and the number of leafhoppers recognizable in them. The average number of leafwere |
