264 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



near the base of the plants or their horizontal roots and in depths 

 varying from one-quarter of an inch to three inches. The depth of 

 the pupal cells seems to be determined largely b}^ the amount of 

 moisture in the soil. During dry hot weather they pupate deeper 

 than during wet weather. 



The period of larval growth varies from about three weeks in mid- 

 summer to six weeks or more in the fall. The pupal period extends 

 over about four da^^s in mid-summ.er and may be extended over two 

 months in the fall. Pupae have been found in the ground as late as 

 the first week in January and these must have remained there in this 

 stage since the first of November. 



The first generation of adults appears about the middle of June. 

 By this time practically all of the over-wintered beetles are dead. 

 Oviposition for this brood extends practically into July and by thi& 

 time the adults of the second generation begin to appear. A third 

 brood begins to appear during the last of August and adults continue 

 to emerge until stopped by cold weather in the fall, usually about the 

 first of November. There is considerable overlapping of broods during 

 the latter part of the season and there is probably a partial fourth 

 brood. 



Natural Enemies 



Climatic conditions seem to be the principal natural check upon 

 the multiplication of this insect. A rainy winter with occasional 

 cold snaps undoubtedly results in a high mortality. In an experiment, 

 under what seemed to be excellent conditions for hibernation, only 

 11 per cent of the beetles survived the winter. The character of the 

 growing season also influences the rate of multiplication. A few 

 beetles are killed by a fungus, probabh^ Sporotrichum, and eggs in 

 cages frequently become covered with a greenish mould and fail to 

 hatch. A small reddish mite was found clinging to a recentlj^ hatched 

 larva in a cage. Mr. G. G. Ainslie has noted that small mites appar- 

 ently injured the eggs. Ants have been observed ca/rying off larvae 

 after they had been dug up. A Spring-tail, as yet undetermined, seems 

 to kill pupse when the ground becomes cold in the fall. The only 

 internal parasite thus far reared is the Tachinid, Celatoria diahroticce,. 

 which kills a small percentage of the beetles. 



Damage 



The amount of damage caused hy the larvae of the bean-leaf beetle 

 is difficult to estimate. When the larvae appear while the plants are 

 young and before the nodules have developed, the roots suffer seriously. 

 When the nodules have begun to develop the larvae then attack them. 

 Nodules appear first on the tap root and these are frequently all 



