106 



The Mechanism of Evolution in Leptinotarsa 



was greater than at Cuernavaca. The greatest difference in the locations is in 

 the water-relation of the organisms. At Orizaba the relation is one of high 



Table 8. 



Moath. 



April 

 May- 

 June 

 July 

 Aug. 

 Sept. 

 Oct. 

 Nov. 



CUERNAVACA, 1905. 



Period. 



20 to 30 

 1 to 10 



11 to 20 



21 to 31 

 1 to 10 



11 to 20 

 21 to 30 



1 to 10 

 11 to 20 

 21 to 31 



1 to 10 

 11 to 20 

 21 to 31 



1 to 10 

 11 to 20 

 21 to 30 



1 to 10 

 11 to 20 

 21 to 31 



1 to 10 

 11 to 20 



Atmometer. 



(Fig. 5), 

 av. daily loss 



in c. c* 



107.4 

 119.8 

 112.2 

 98.7 

 92.5 

 66.4 

 64.3 

 61.7 

 54.5 

 51.3 

 54.1 

 64.5 



Free wateri 

 surface, 



av. daily loss 

 in c. c.f 



93.2 

 108.7 

 100.4 

 91.0 

 84.1 

 55.1 

 54.9 

 53.4 

 47.6 

 40.1 

 41.1 

 58.7 



Max. loss 

 in c. c. 



Free 

 H,0. 



Atm. 



Min. loss 

 in c. c. 



Free 

 H,0 



87.4 



80.1 



117.4 



148.1 



141.0 



117.1 



108.1 



80.0 



80.0 



81.0 



73.0 



77.0 



81.0 



96.4 



124 is 

 121.1 

 127.1 

 129.4 



141 ! 4 



87.2 

 101.4 

 98.4 

 84.5 

 77.0 

 19.7 

 30.4 

 42.0 

 29.3 

 35.8 

 37.7 

 39.9 



6i!2 

 50.1 

 60.3 

 69.9 



74.1 



ORIZABA, 1906. 



April 



May 



June 



July 



Aug 



Sept. 1908.. 



Nov. 1905.. 

 Jan. 1910.. 



20 to 30 

 1 to 10 



11 to 20 



21 to 31 

 1 to 10 



11 to 20 

 21 to 30 



1 to 10 

 11 to 20 

 21 to 31 



1 to 10 

 11 to 20 

 21 to 31 



1 to 6 

 10 to 18 



1 to 5 



7 to 14 



77.0 

 79.4 

 87.4 

 60.1 

 43.1 

 31.1 

 31.7 

 33.5 

 21.4 

 20.4 

 23.6 

 31.2 

 33.4 

 34.5 

 33.5 

 37.7 

 45.7 



65.2 

 74.3 

 76.1 

 44.2 

 32.1 

 20.9 

 24.3 

 29.2 

 17.3 

 14.1 

 26.1 

 26.4 

 27.7 

 30.1 

 31.1 

 34.6 

 39.4 



61.0 

 66.1 

 71.4 

 11.9 

 1.7 

 0.4 

 0.0 

 0.0 

 0.0 

 0.7 

 0.9 

 0.0 

 0.0 

 0.0 

 4.1 

 0.0 

 0.0 



* Evaporating surface = 800 sq. cm. heavy filter paper hung vertically in open. 

 t Evaporating surface = 800 sq. cm. in dish, 40 by 20 cm., in open in sun. 



water-content in the medium, with relatively low evaporation-rates, hence the 

 prevailing type of plants and animals characteristic of moist habitats in the 



