363 



The proper beginning point, for a study of life histories in relation to en- 

 vironment, Is the adult, since it places the eggs under conditions to which the 

 later stages are subject. In the work In hand, however, studies made of the 

 adult were not sufficient to warrant such a procedure; therefore, to illustrate 

 the methods used, the pupa will be taken up first. 



(A) GENERAL RESULTS ON PUPAE. 



The series of approximately constant temperature experiments was 

 conducted with a total of 4,000 larvae belonging to the following genera- 

 tions : summer 1917, spring 1918, spring and summer 1919 and 1920. Of 

 these, about 2,000 pupated and 1,100 emerged. About 800 larvae from 

 the 191T, 1918, and 1919 generations were started in variable tempera- 

 ture experiments. Of these, 515 pupated and 370 emerged. About 1,200 

 larvae, chiefly of the 1921 spring generation, were used in experiments 

 on hibernation and related processes. Abottt 800 of these emerged. The 

 rather high mortality brought the net results of handling 6,000 larvae 

 down to about 50 per cent of our expectation. The 3,000 pupae, however, 

 yielded an ample mass of data from which to draw fundamental 

 conclusions. 



Tables XII and XIII show full data on the pupae reared under 

 approximately constant temperatures, and Tables XVIII and XIX show 

 the data from the variable-temperatures. The experimental methods and 

 apparatus are described on pp. 426-435. The containers in which 

 the pupae were held are described on p. 432 and illustrated in Fig. 

 34. N^early all containers were ventilated, and records included air 

 velocity, evaporation from the porous cup atmometer, humidity, and 

 temperature, all of which are shown in some detail in appropriate col- 

 umns. The designations given in the first colutnn of each table refer to 

 stocks, places, and conditions as explained below and in notes at the 

 proper places.* 



Each figure for pupal life in days is the average for the number of 

 individuals pupating. An idea of the variation may be had from the data 

 (Table XII) indicating the extreme range in days (the dift'erence between 

 the longest and the shortest time) ; also from the range for 80 per cent 

 or more of the pupae. This 80 per cent group merely excludes the 

 extreme, though their inclusion often does not modify the average 

 greatly. The winter treatment is given, and the time intervals between 



* In addition to the letters used to designate the various experimental chambers, 

 as explained in the description of methods (p. 434), the following- letters were used 

 with meanings as indicated : For Humidity D. dry ; M, medium moist ; W. moist ; 

 WW, very moist. 



For air movement and evaporation: H, high air velocity; I, intermediate air 

 velocity ; L, low air velocity. 



For light: D, dark; L, light; LL., lighter. 



For unit R (an ice-box) : L, lower shelf; L,L, lower left shelf; M, middle shelf; 

 T, top shelf, etc. 



O is out of doors ; P, in the glass-roofed house ; NC, indicates no container cov- 

 ered the sticks in which the larvae and pupae were held. 



a, b, c. etc.. indicate different experiments under the same or approximate con- 

 ditions and from the .'^me generation but started on different dates In order indicated 

 by the alphabet. 



NV indicates that no air was forced through the container, lience not ventilated. 



