August, '22 HOWARD: MEXICAN BEAN BEETLE 275 



Mr. N. F. Howard: No sir. 



Mr. G. E. Sanders : There is an interesting point there. Magnesium 

 arsenate proved quite a bit safer than calciiim. I would like to hear the 

 chemical reason for that from Professor Moore. 



Mr. William Moore: The conditions in the South, south of the 

 James River, in geological siixveys show that the natural water con- 

 tains an excess of strong bases over strong acids, producing an alkaline 

 water, due to sodium carbonate. Most if not all alkaline materials 

 which give an alkaline reaction with phenolphthalein will react with 

 acid lead arsenate. 



It is of interest that although entomologists have been using lime for 

 twenty years with lead arsenate to reduce the amoimt of soluble arsenate, 

 the reaction of the lime actually increases the amount of soluble arsen- 

 ate when mixed with acid lead arsenate. Concerning magnesiimi ar- 

 senate I believe there has been some objection by the Insecticide Board 

 because of its injury. Mr. Howard reports from the South that mag- 

 nesium arsenate gave less injury than with calcium arsenate. In the 

 case of magnesium arsenate, the compound itself is somewhat more 

 soluble than calcium arsenate. If there were no further decompositions 

 more injury would be obtained with magnesium arsenate than with 

 calcium arsenate but when the climate is such as to favor the action of 

 carbon dioxide on the calciimi arsenate, you get a decomposition of the 

 calciimi arsenate and it then becomes more injiirious than the magnesium 

 arsenate. 



President George A. Dean: We will now listen to Mr. W. E. 

 Britton. 



TOBACCO PLANT INJURED BY THE SEED CORN MAGGOT 



By W. E. Britton, 



State Entomologist, New Haven, Conn. 



On the plantation of the Windsor Tobacco Grower's Corporation at 

 Windsor, Conn., a large acreage of tobacco is grown imder cloth for 

 cigar wrappers. In one field of forty acres, one half, or twenty acres, 

 soon after setting, had the plants injured by maggots which tunneled 

 into the sides of the stems just below the surface of the ground. In 

 som.e cases the injiiry was very slight and inconspicuous and showed 

 only as a sm.all pin-hole in the side of the stem, but in other cases the 

 tunnel was considerably enlarged inside the stem and extended upward 

 or downward in the pith for half an inch or more. A slight decay had 

 started around the injury in some plants. The manager examined and 



