351 



and the pupal stages are shorter than when following an autumn and 

 winter with less precipitation. Compare graphs for 1915. 1916, and 19n 

 in Fig. 3 showing this relation. In all cases, the pupal hfe is long in all 

 the later formed pupae. A comparison with Glenn's charts 1, 2, and 3 

 shows that the great mass of pupae had emerged previous to those whose 

 mid-date of pupal life came on May 15. It will be seen that the pupal 

 life of the large groups was longer than normal in 1915, following a dry 

 autumn and winter, and shorter than normal in 1916, following a we. 

 winter; 1917 is intermediate in length of pupal life and in amount of 

 autumn rainfall. 



The difference in length of the pupal stage is quite marked, even in 

 the case of Glenn's pupae which were not exposed to rain. The most 

 marked case was that of the 191T-18 larvae which hibernated in very dry 

 conditions in the laboratory and were put out of doors in the spring; the 

 actual time was 119 per cent of the standard time. This is higher than 

 any other recorded. 



b. Combinations of Rainfall and Seasonal March of Temperature. 



The annual march of temperature and rainfall by months for a j'ear 

 in which the codling moth flourishes in southern Illinois are shown in 

 Fig. 4, graph A, beginning with September of the preceding year; the 

 autumn is rainy, and the spring only moderately so. In graph B, which 

 is for a year when the codling moth is scarce in southern Illinois, the 

 autumn is very dry, and the spring very wet. The summer of graph B is 

 cooler than that of graph A ; otherwise there is little difference in mean 

 temperature. Graphs A and B in Fig. 5 show, respectively, the general 

 limits of temperature and rainfall for the months of years when codling 

 moths are scarce and abundant ; that is, the mean monthly temperature 

 and rainfall for such years fall within the areas marked. Data for the 

 year 1914, when codling moths were more abundant and spraying seemed 

 less effective than in many years, constituted the chief basis for the estab- 

 lishment of the limits shown in graph A of Fig. 5. Answers to a ques- 

 tionnaire sent out by Mr. W. P. Flint to a number of orchardists showed 

 moths abundant near Mount \'ernon and Charleston in 19"?0, and the data 

 for most of the months fit the diagram very well. ( See Fig. 30 p. -i'li. ) 

 Data for 1923, a "scarce" year, were taken as a model for most 

 of the months shown in graph B of Fig. 5, but by being extended they 

 have been made to include two-thirds of six years in localities where 

 moths were declared scarce by orchardists. The crosses in Fig. 4 are the 

 centers of the areas outlined in Fig. 5. (See Fig. 25 and explanation.) 

 Graph A of Fig. 6 is a diagram of similar data for 1921-1922 at Olney, a 

 year which A. J. Wharf marked "scarce early" and "abundant late" ; it 

 shows a fairly favorable autumn, an unfavorable spring, and a favor- 

 able summer. The great influence of rainfall is here illustrated by the 

 fact that the temperature for some months of this year (and for some 

 of the months shown in Fig. 30) was as low as, or lower than, for the 

 corresponding months in the years in which the moths were scarce. 



