64 NATURE STUDY AND LIFE 



fresh meat be exposed for an hour in warm weather, it 

 will generally be found to have masses of whitish-yellow 

 eggs on it of the bluebottle, or blow, fly. 



It is not intended that children shall make breeding 

 experiments with flies. Such disagreeable work may be 

 left, in general, for specialists, but the two lessons that 

 every child should learn are that filth of various sorts 

 breeds flies and that in spite of the best we can do in 

 keeping our premises clean, we need the help of insectiv- 

 orous animals. Ask children to study what the swallows 

 are doing when circling about a herd of cattle, what the 

 phoebe and kingbird do when they dart from their perch 

 and you hear their bills snap. What other birds eat 

 flies .'' Let some child who has a tame bat see how many 

 flies it will eat. The writer had one that ate 243 at a 

 meal, but it died soon after. Let the children watch the 

 toads about the back doorstep to see how many flies one 

 of them may eat in a day. One little girl the writer 

 knows counted while a toad snapped up 128 flies within 

 a half hour. A tree frog is a most interesting pet and a 

 wonderful flytrap. 



Mosquitoes. — These insects furnish a great field for out- 

 door study, careful observation, and experiment. There 

 are thirty different species described for North America 

 (for the more complete study of which refer to Bulletin 

 No. 25, United States Department of Agriculture). It is, 

 however, only necessary to know the life story of any one 

 kind to do efficient and valuable work. The eggs may be 

 found at any time in warm weather on the surface of stag- 

 nant water ; they hatch generally in the afternoon of the 

 same day they are laid and pass their larval and pupal 



