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tion of bat guano from the same species. This, I think, would attract any 

 of these animals in the vicinity and they probably would adopt the building 

 as their own. This is the species of bat which inhabits the bat guano caves 

 of Texas. These bats and their excrement have an extremely offensive odor, 

 which is strongly apparent about any house where they live. 



In reference to the practicability of getting results by building bat roosts 

 iri New Jersey and Pennsylvania, I would say that there is no species of bat 

 belonging to the climatic condition found in those States which colonizes in 

 any such swarming numbers as does the bat inhabiting Dr. Campbell's roosts. 

 Consequently I do not think there would be the remotest chance of success- 

 fully attracting any considerable number of these animals. Furthermore, 

 even should a considerable number of the bats inhabiting the Middle 

 United States be gathered in one locality, the knowledge of their food habits 

 would indicate that their effeGt on mosquitoes of the district would be very 

 slight. 



E. W. Nelson, 

 Acting Chief, Biological Survey. 



In conclusion, I do not wish to be understood as entirely con- 

 demning the bat-roost idea. Doctor Campbell has been very 

 courteous to me and to the Bureau workers, and is enthusiastic 

 about his plans. But it is obvious to me that rigid scientific 

 experimentation must still be carried on before any of his con- 

 clusions are accepted, and, frankly, the field is not sufficiently 

 promising to induce the government entomological service to 

 spend money in this direction which can be used for more 

 pressing needs. 



It appears to be plain from Mr. Nelson's expert opinion that 

 people in New Jersey need not expect any great reduction in 

 mosquitoes to follow the erection of bat roosts. If there is any 

 one here who- is still sanguine in this direction, I would urge 

 him to erect a roost at his own expense and have the most care- 

 ful scientific study of the results made by your very able State 

 Entomologist, Doctor Headlee. 



In other words, the evidence in regard to southern bats is yet 

 very conflicting, while even experimentation with northern bats 

 seems not to justify the expense. Bats, however, do feed on 

 injurious insects, and very likely should be protected, as the State 

 of Texas is being urged to do. 



The President — This paper of Dr. Howard's is particularly 

 interesting at this time, inasmuch as representations have been 



