December, '21] morrill: thlrberia boll weevil 475 



on the subject. The following is a copy of the questionnaire' with the 

 most terse representative answers : 



"A valuable agricultural crop A is grown in valleys near mountain 

 ranges where a closely related plant B is widely scattered with a natu- 

 ral range extending down to within less than five miles of cultivated 

 land in some cases. Plant B is known to be generally infested with 

 two destructive insect pests, a weevil X and a moth larva Y which 

 are known to attack the cultivated plant, A, whenever available, ex- 

 hibiting no noticeable preference between the two food plants. In- 

 vestigations of these two insects by state and U. S. Government ento- 

 mologists have lead to warnings concerning the danger to the cultivat- 

 ed crop A. 



"Plant B grows scatteringly over thousands of square miles of 

 drainage country and investigations have led to the conclusion that 

 infested parts of the plant are frequently washed down by water flow 

 from the higher altiudes. In some cases, the water even when in 

 considerable quantities disappears in the sands in the lower ends of the 

 canyons leaving debris which is supposed to frequently include parts of 

 plant B infested with X. In such cases it is logical to suppose that the 

 specimens of the weevil X thus transported are attracted by plants B 

 growing in the vicinity and the cultivated crop A is thus under natural 

 conditions protected against the danger of infestation by flights which 

 would be forced if none of the wild food plants B were naturally growing 

 in the vicinit}' near where the infested i:)lant material is deposited by 

 the water. 



■ ' Plant B naturally produces a great abundance of food for all insects 

 which attack it and under normal conditions it is evident that migrations 

 of such insects never result from, a shortage of food supply. This 

 abimdance of food has doubtless in the past acted as a protection to 

 crop A. 



"The adult of insect Y is unknown but the larva is robust and 

 apparently is that of an active noctuid moth which has been supposed 

 to be capable of flying a considerable distance. Two entomologists, 

 specialists on insects affecting crop A who conducted the principal inves- 

 tigation of insects affecting plant B reported in an article published in a 

 scientific journal that insect Y was even more destructive to its food 

 plant than insect X, the inference being that Y was even more to be 

 feared as a potential enemy of crop A than was insect X. 



'Questions 5 and 7 are omitted in order to save space. 



L 



