THE MEXICAN BEAN BEETLE 23 



cent liiunidity. The food was kept fresh in all conditions Ijy jslacing the leaf 

 petioles in water. 



The influence of alternating temperatures with 32° and approximately con- 

 stant moisture surroundings was more favorable for larval development than 

 constant high temperature (Table VI, 32°). When 27° was alternated with 

 32°, sixteen hours of exposure daily in the higher temperature proved to be 

 very severe on the pupae as well as on the larvae. Eight hours' exposure 

 daily was largely overcome by the cooler condition, as only a few larvae were 

 killed. The use of 22° as the alternating temperature with. 32° when the 

 moisture was high gave results indicating that the influence of the low tem- 

 perature overcame the adverse effects of the high in proportion to the hours 

 of exposure in each. When dry conditions were used, the data were similar 

 to those obtained in the check environments. The humidities in the 17°-32° 

 environments were 32 and 50 per cent, and while both are low, they cannot 

 be considered as constant. Good rearings were secured in these conditions. 



The adults reared in the 17°-32° alternating environments showed a high 

 percentage of distortion, only about 30 per cent appearing to be normal, in- 

 dicating that most of the development took place in the higher temperature. 

 Abdominal disfigurement was evident in about half of these insects. A few 

 of the beetles were reduced in size. When 22° was alternated with 32°, six- 

 teen hours of exposure daily at 32° produced about 60 per cent of normal 

 individuals in both high and low humidity, and eight hours of exposure daily 

 developed 80 per cent of adults normal in size. The alternation of 32° and 

 27° produced 12 per cent of normal adults with sixteen hours of exposure 

 daily at the high temperature, and 80 per cent of normal beetles with eight 

 hours' treatment daily at this temperature. Many of the adults were reduced 

 in size in this latter environment. 



The results of alternations about 27° with high humidity were quite uniform 

 and favorable to development of the larvae of the bean beetle with the excep- 

 tion of sixteen hours' exposure daily at 32°, which has been discussed pre- 

 viously (Table VI, 27°). The adults reared in 27°-22° temperature condi- 

 tions were normal with eight hours' exposure daily to 27°, but about 40 per 

 cent of them showed some distortion of the wings and elytra following sixteen 

 hours' exposure daily to 27°. 



The influence of alternating temperatures about 22° with approximately 

 constant moisture environments is shown in Table VI, (22°). The unfavor- 

 able effects of both high temperature and low humidity are shown, fewer 

 larvae reaching maturity with an increase in the number of hours at 32° and 

 in the lower humidities. However, a sufficient number of larvae developed 

 in all of the environments for the beetle* to maintain itself in economic num- 

 bers. Most of the adults that developed were normal in size and contour in 

 all conditions below 32°. 



The data in Table VI (17°) show the influence of alternations in tempera- 

 ture about 17°. The lengthened developmental period shows that these en- 

 vironments were inferior to the 22° and 27° conditions for rapid growth, 

 although the death rate was very low. The adults reared under the 17° con- 

 stant temperature environment were large and normal in appearance, while 

 many of the beetles reared in the 17°-32° temperature comliinations were 

 greatly distorted. 



The melanism that occurred under constant exposure at 17° did not appear 

 when the larvae were alternated between 17° and higher temperature en- 



