INTRODUCTION. 17 



best essays based on original observations and experiments 

 on the destruction of mosquitoes and flies by other insects. 



" The following suggestions are made as to the direction 

 in which the investigation should be carried and the 

 essay formulated. 



"1. Observations and experiments upon various insects 

 that destroy mosquitoes and house flies, stating the method 

 of and capacity of destruction. 



*' 2. Observations and experiments to determine the best 

 dragon flies to be artificially multiplied for the two ab». e 

 named objects — probably species of ^schna, Libcllula, 

 or Diplax. 



" 3. Give detailed statements of the habits and life his- 

 tory of the species chosen, based on original and careful 

 experiments and observations. 



"4. Suggest a plan for breeding the insects in large 

 numbers ; with a sketch of apparatus, and estimated cost 

 of producing them per thousand. 



" 5. Formulate a plan for using the insects in the larva, 

 pupa, or perfect state for the destruction of mosquitoes 

 and flies (a) in houses, (b) in cities, (c) in neighborhoods. 



" The prizes will be awarded after careful consideration 

 by Dr. Henry C. McCook, Vice-President of the Acad- 

 emy of Natural Sciences of Philadelphia and Vice-Presi- 

 dent of the American Entomological Society, and Dr. J. 

 S. Newberry, President of the New York Academy of 

 Sciences, Professor of Geology of Columbia College, and 

 late Chief of the Geological Survey of Ohio. 



" In awarding the prizes, clearness of statement obtained 

 by accompanying sketches, and new and purely scientific 

 facts in the life history of the Libellulidse, of whicli so 

 little is known, will be duly considered. All the essays 



