INSECTS OF THE HOUSEHOLD 67 



the aquarium, but it cannot stand on oil. Since all the 

 mosquitoes of a neighborhood must come to the water to 

 lay their eggs, and since all the eggs and wrigglers are 

 killed, this is one of the easiest ways to rid the place of 

 mosquitoes. It has been tried on a large scale and under 

 all sorts of conditions with remarkable success, so that 

 any inland community, not surrounded by interminable 

 marshes which cannot be drained, may easily rid itself of 

 the mosquito pest. The amount of oil required is an 

 ounce for fifteen square feet of water surface, and it will 

 not require renewing for from one to two months, unless 

 washed off by heavy rains. As soon as live wrigglers can 

 be found, the oil should be applied again. 



The children have now learned two ways of exterminat- 

 ing mosquitoes. Discuss and compare them, drawing out 

 what the class thinks is the easiest, cheapest, and most 

 effective method. Bring out the fact that one is man's, 

 the other is nature's, method. 



As the hunt for .mosquitoes and wrigglers progresses 

 in the spring, have each child make a map of some part 

 of the district, preferably his own lot, block, or farm, 

 marking plainly all the pools and streams in which mos- 

 quitoes are and are not found. Have the children then 

 go over the ground very carefully again, to see if they 

 can discover why mosquitoes are abundant in some places 

 and not in others ; they may take their maps with them 

 and do this on an excursion. Do the fishes make the 

 difference? Do frog arid toad tadpoles 1 keep the water 



1 The writer has seen toad tadpoles eat mosquito larvae in an aquarium 

 and has observed that in two water-lily tubs standing side by side the one 

 without tadpoles swarmed with wrigglers, while the one stocked with tad- 

 poles contained none or very few. 



