10 MASS. EXPERIMENT STATION BULLETIN 261 



to be in proportion to the number of hours the beetles were kept in the higher 

 temperatures, indicating that vcrj- little, if any, stimulation to egg develop- 

 ment occurred at 17°. 



Varied Conditions. A number of experiments were planned to ascertain the 

 effects of definitelj' varied conditions on egg yields. One factor, either tem- 

 perature or moisture, was held constant, or approximately so, while the re- 

 maining one was varied. Temperature environments, which were easily con- 

 trolled, ranged from 17° to 32° at intervals of 5° (Table II). Varied 

 temperature conditions were obtained by transferring the experimental cages 

 from one cabinet to another at definite intervals, a twenty-four hour day 

 being divided into eight and sixteen hour periods. This process of alternation 

 was continued day after day, so that each cage was in one environment for 

 eight hours, another sixteen, then back to the eight hour condition, and so on, 

 for the duration of the experiment. Moisture environments in two cabinets 

 with different temperatures could not always be maintained with the same 

 humidities, so that percentages of moisture as similar as possible were chosen. 

 Thus combinations of high humidity percentages, as 86 and 92, 80 and 92, and 

 80 and 86, are considered approximately equal in their effects on egg produc- 

 tion. Likewise combinations of low humidity percentages, as 32 and 40, and 

 40 and 50, can be considered as having similar effects on egg development. 

 The one humidity combination of 32 and 50 per cent is considered as a varied 

 moisture environment within the low humidity region. The experimental cages 

 were transferred from one cabinet to another, as described above, when the 

 effects of varied moisture conditions were sought. Data obtained from the 

 cages that were kept in the constant environments are 23laced under each 

 heading for comparative purposes. In each instance the beetles were taken 

 from the same stock cages as those used in the varied surroundings. The 

 data are arranged about the temperatures 32°, 27°, etc., so that a direct com- 

 parison can be made with the results from the constant conditions. This 

 necessitates the repetition of son^e of the data in more than one place, but 

 the discussion is not repeated unless necessary. An expected number of eggs 

 was calculated from the data secured under constant conditions and placed 

 in the last colun.n of the table. These figures are based on the ninnber of 

 hours the beetles were kept in the respective temperatures and in high and 

 low humidity, and serve as an aid in comparing the actual results obtained 

 in the varied conditions with those secured in constant environments. A 

 temperature of 37° was excluded from the varied experiments Ijecause of the 

 disastrous results obtained imder constant conditions. 



The results obtained from varied temperature environments with 32° are 

 given in Table II (32°). The humidity combinations, exce^jt 32-.50 and 50-32, 

 are considered as approximately constant. The total number of eggs laid by 

 the beetles exceeded the expected number in every instance, but the excess 

 was much greater in the high humidities. The reduced egg yield at 32° in 

 the high moisture environments (Table I) seemed to be largely offset when 

 the alternating temperature was reduced to 27° for sixteen hours daily, but 

 was still evident with only eight hours' exposure daily at 27°. When 22° was 

 used as the alternating temperature with 32°, the numbers of eggs laid were 

 rather uniform in both high and low humidities. The results, 2057 to 2231 

 eggs, compared favorably with the number laid, 2217, in the 32° constant 

 temperature cabinet with low humidity. When 17° was used as the alter- 

 nating temperature in connection with low humidity, the number of eggs 



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