40 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



leaves were sprayed with calcium arsenate, magnesium arsenate, and 

 lead arsenate at the rate of i pound of powder to 50 gallons of water. 

 The calcium-arsenate mixture also contained lime at the rate of 1.5 

 pounds to 50 gallons of water (table 7). 



The results given in table 7 clearly show that arsenicals are repel- 

 lent, but not sufficiently so to prevent the foliage from being eaten. 

 Lead arsenate was most repellent, magnesium arsenate was less so, 

 and calcium arsenate was least repellent. The word " deterrent " is 

 probably the better expression in this case. 



Table 9. — Tests to dctcnn'me zvlucthcr zvatcr extract and steam distillate of 

 bean leaves are attractive to Mexican bean beetles 



(7) Bean foliage sprayed ivith sivcetcncd magnesium arsenate is 

 more attractive than foliage sprayed with non-sweetened magnesium 

 arsenate. — To determine whether the above is true 16 series of tests 

 were conducted by using magnesium arsenate ( i pound to 50 gallons 

 water) with molasses added at the rate of 2, i, and ^ gallons to 50 

 gallons of the spray mixture (table 8). 



The results given in table 8 once more show that sweetened food is 

 preferred to non-sweetened food. 



On September 30 four small bean plants, each bearing six leaves, 

 were sprayed. Two of these were sprayed with magnesium arsenate 

 alone and the other two with a mixture of magnesium arsenate and 

 black-strap molasses (i to 50). One plant sprayed with the non- 

 sweetened mixture and one with the sweetened mixture were put to- 



