THE MEXICAN BEAN BEETLE 5 



ginia and Ohio in 1923; Pennsylvania, Indiana, and Mississippi in 1924.; Mary- 

 land in 1926; New York, Michigan, and Ontario in 1927; Delaware and New 

 Jersey in 1928: and Connecticut and Massachusetts in 1929. Unless some 

 unusual climatic condition develops, the pest will probably reach eastern 

 Massachusetts in the next two or three vears. 



Effects of Temperature and Moisture Under Controlled 

 Laboratory Conditions 



Bioloffica] Mnterial. 



Adults find Larvae. A stock cage of adults, feeding on growing plants, was 

 kept in the greenhouse at all times. When experiments were started, beetles 

 of about the same age and with similar previous history were used. The in- 

 sects used in the original set of experiments were collected in late September 

 and were of unknown ages and previous history. Care was used to propor- 

 tion these beetles among the experimental cages according to the color, as the 

 general liody color becomes darker with age. The experimental cages were 

 made of glass tubing about two inches in diameter, with the ends covered 

 with cheese cloth, which permitted free access of air currents. The final 

 method used for keeping the food fresh was to place the leaf petioles in a 

 small vial of water. A grooved cork was used, to prevent evaporation from 

 the vials aflfecting the cage conditions. By changing the leaves twice daily, 

 the food was kept in excellent condition. Whenever the above method of 

 handling the plants was not used, it is so stated when that experiment is 

 considered. The larvae were cared for in a similar manner. 



Eggs and Pupae. The eggs were handled by cutting away the surrounding 

 leaf tissue and placing them in open vials. The drying of the leaf particles to 

 which they were attached, and the consequent wrinkling sometimes injured a 

 few eggs, and at times prevented some of the larvae from emerging, but this 

 factor was considered when tabulating results. The pupae were treated 

 similarly. 



Phi/.sical Factors Involved. 



Temperature is an extremely important factor in the life of the bean beetle. 

 It is closely allied with moisture and does not affect the insect as a single 

 factor except when approaching the high and low temperature limits. Mois- 

 ture is as important to all stages of the insect as temperature, and in some 

 stages is more so. It probably affects the insect principally through evapora- 

 tion. The evaporation rate is in turn influenced by the temperature and air 

 movement. The velocity of the air is extremely important, as the tempera- 

 ture and relative himnidity about the plants approach a state of equilibrium 

 with the environment away from the plants in direct proportion to the move- 

 ment of the surrounding air. No direct effects of light on the bean beetle 

 have been observed, but light is taken in indirectly through the food. It is 

 extremely important to keep the insects supplied with fresh food. The larvae, 

 especially, show signs of restlessness shortly after the plants begin to wilt. 



Description of Apparatus. 



A well-insulated cabinet containing six separate compartments was used. 

 Each section was two feet by two feet by three feet in size. The top was 



