62 DRAGON FLIES VS. MOSQUITOES. 



and bats. Harvey ^^ has found six liundred mosquitoes 

 in the crop of a niglit hawk ; evidently these birds are 

 worthv of encouragement. 



We know that mosquitoes are attracted to our houses 

 by the iUumination from within ; therefore, if lights are 

 placed away from our habitations, in suitable localities 

 near marshes and ponds, and arranged as in Plate VI., Fig. 

 2, with petroleum in the tray, they may be the means 

 of destroying myriads of these tormentors. Fungoid 

 growths have not been tried upon Culex ; we observed, 

 however, an interesting species of Algae on the head of 

 many larvae. 



No very promising methods remain to be discussed, 

 save the Odonat cultivation and the oil treatment. 



The former is of the most importance from the stand- 

 point of this essay, as it is the plan which brought forth 

 the call for the contest. AVe regret that our ciireful and 

 continued study under all conditions and favorable cir- 

 cumstances show that the habits of the Odonata remove 

 them from the possibility of close contact with the Culici- 

 dae and their tastes are such as to make the latter unsatis- 

 factory food for them. However, with a view to the pos- 

 sibility that others may not look upon this problem as we 

 do, we give the outcome of our experience in rearing the 

 Odonata. They must be kept in slowly running water, 

 and the tanks in which they are bred must be free from 

 all aquatic predatory insects, and so screened as to prevent 

 the ingress of these or of frogs. Fish must be kept out, 

 and netting should be spread so that birds may not attack 

 them when they emerge from the pupae. Owing to their 

 cannibalistic tendencies, the larvae should be placed in 

 large tanks with a limited number in each, and fed care- 



