Apeil 12, 1918] 



SCIENCE 



373 



TABLE I (continued) 



g 8 



April 18 

 April 18, 

 April 23. 

 April 23 

 April 26 

 April 26 



May 10 

 May 10 

 May 14 

 May 14 

 May 15 

 May 15 

 May 17 

 May 17 

 May 18 

 May 18 



2 6 



3 '23 

 : S 

 I 3 



6 

 3 131 



Green 



John 



Green 



John 



Green 



John 



Green 



John 



Green 



John 



Green 



John 



Green 



John 



Green 



John 



* Indicates eggs. 



been given to the total animal population of 

 definitely measured areas of land. At the sug- 

 gestion, and with the aid and assistance, of 

 Dr. V. E. Shelford, of the University of Illi- 

 nois, a study was made of the animal popula- 

 tion of two vacant lots, a block apart, in Cham- 

 paign, Illinois, over a period from September, 

 1916, to May, 1917. The lots were on John 

 and Green Streets, adjoining the Illinois Cen- 

 tral Eailroad. They had not been burned over 

 for at least a year, and despite the encroach- 

 ments of debris from the railroad and nearby 

 houses, were essentially wild, being covered 

 with grass, sweet clover, dandelions, burdocks 

 and other weeds, while the Green Street lot 

 had a thicket of young honey locusts on one 

 side, and that on John Street had a brook 

 bordered by osage orange and willows running 

 along one side. 



The apparatus used was very simple, con- 

 sisting of a tin pail with the handle and bail 

 removed, and a screw top, an inch in diam- 

 eter, soldered into the bottom, through which 

 the anesthetizing agent could be introduced. 

 The sharp edges of the pail, where the bail 

 26, p. 637, 1907; Osborn, H., " Leaf -hoppers of 

 Maine," Maine Agr. Expt. Sta. Bull., No. 238, 

 pp. 81-160, 1915. 



t Indicates partly eggs. 



had been cut away, would sink into soft earth, 

 and with the aid of a big knife, vegetation and 

 hard earth could be cut through, so that the 

 animal population of that small area woiild 

 be imprisoned in the inverted pail. A consid- 

 erable amount of chloroform or ether was 

 added through the screw top, and after clear- 

 ing away the surrounding vegetation and 

 debris, sufficient time would have elapsed so 

 that all the active animals were anesthetized 

 and the pail could be taken up without fear 

 that any of them would escape. The vegeta- 

 tion within the circle was picked to pieces 

 and shaken over newspapers, weed stems split 

 up, the surface of the earth left bare was care- 

 fully examined and finally all the earth to a 

 depth of six inches was dug up and sifted over 

 newspapers, so that all animals large enough 

 to be visible to the naked eye would be sorted 

 out. The surface area covered by the pail 

 was .518 sq. ft., which, multiplied by 84,092, 

 gives the population per acre. Two examina- 

 tions (one for each lot) were made daily when 

 time was available, or the g:round not too wet 

 and sticky or frozen. The results are given 

 in the table. 



The area enclosed by the pail (.518 sq. ft.) 

 is so small that there will necessarily be a wide 



