EXPERIMENT STATION BULLETINS. 255 



used in the map are as follows : north woods region, north marsh 

 region, Delta region, lower river flats, athletic field region, campus, river 

 woods, railroad pond. 



The north woods region comprises a piece of woods with ponds in it, 

 some swamp with trees standing in the water, and a long ditch which 

 ordinarily dries up in summer. 



The north marsh region includes about 40 acres of marsh with stand- 

 ing water over a good portion of it, especially around the borders. 

 This region also includes several ponds, as shown in the map. 



Delta region contains a number of pools in second-growth wood and 

 some in the open. 



The lower river flats contain a number of long flood ponds near the 

 river. They dry up before many mosquitoes emerge. 



The athletic-field region contains many ponds with trees growing in 

 them. They are protected from the wind by the trees and offer good 

 breeding-places. 



The campus contains the pond by the woman's building, a good-sized 

 pond full of ornamental water-plants and covered, from the middle of 

 August on, with confervae and other vegetation, unless artificially re- 

 moved; the botanic garden ponds, which contain many native plants 

 and which would make a fine breeding-place for mosquitoes but for the fish 

 which have been introduced. Beside these ponds there are ponds along 

 the river bank and a group of small tanks for growing water-lilies, etc.; 

 a pond in the elk-park and an open drain which is stocked with minnows 

 and sticklebacks. 



The river woods contain a chain of shallow pools near the river. 

 These pools breed mosquitoes in large numbers. 



The railroad pond is an open pond exposed to the wind and sun with- 

 out any shelter at all. No mosquitoes have been found in it thus far. 



Following is a record of work done with oil: 



The north woods were treated on April 26, May 24, July 11. 



The north marsh region April 26. 



Delta region, April 28. 



The lower river flats, no mosquitoes. 



Athletic field, April 21, May 27, July 10. 



Campus, April 21; along river shore, July 10 same. 



River woods, April 29, May 24, July 15. 



Railroad pond, no mosquitoes. 



Beside these places small transient pools were treated from time to 

 time. During the middle of May mosquitoes appeared in numbers. 



NUMBER OP LARVAE AND PUPAE FOUND IN A GIVEN AREA. 



On April 24, a piece of woods known as the railroad woods was vis- 

 ited by the writer in company with Mr. Barlow. It was intended early 

 in the season to include this region in the experiment but for certain 

 reasons it was deemed inexpedient to do so. However, a count was 

 made of the number of larvae and pupae in the water at that time. The 

 pools were distributed as they ordinarily are in our woodland; several 

 large ponds with small pools around the border. Some of these small 

 pools connect with the main pond and some are cut off by the slow 

 sinking of the water. In these small, shallow pools the mosquitoes 

 swarmed. In a typical one, about fifteen square feet in area, a count 



