hodge] FLIES AS A NATURE-STUDY PROBLEM 89 



and watering troughs. They are suspected as possible carriers of 

 pellagra. 



Mosquitoes are fly-like insects, now well known to carry the 

 germs of malaria — chills and fever, ague — and yellow fever. 



Fleas are practically flies without wings and were long classed 

 with the flies. Each kind of animal is likely to be infested with 

 its peculiar species of flea. The rat flea spreads the germs of 

 bubonic plague from rats to man. Other fleas are being studied 

 to find out which one, if any, transmit the germs of leprosy. 



Tachina and Syrphus Flies are beneficial because they lay their 

 eggs on, or near, other insects and the maggots feed upon and kill 

 them. A number of kinds are being imported by the government 

 to control the gypsy and brown-tail moths. 



Life History of House Fly. (a) Eggs. Will several of the pupils 

 volunteer to find and bring in the eggs? (These may be found 

 about fresh horse manure from April or May to November, or a 

 number of flies may be kept in a cage of screen wire, or mosquito 

 netting, with a glass jar of fresh horse droppings in it, and the eggs 

 be secured in this way. Feed the flies well with milk and watch 

 for them laying, and look for eggs near the bottom of the jar. 



(b) Maggots. If the eggs are secured, the rest of the lite history 

 may be observed as the maggot develops in a glass jar of horse 

 manure. They will transform into puparia, generally at the 

 bottom of the jar, and finally emerge as adult flies. (Nothing 

 puts more fight into a community than these lessons and no one 

 who has worked them through can eat food on which they have 

 seen flies.) 



(c) Time Relations. Keep all dates carefully. In warm weather 

 eggs may hatch in from 12-24 hours, the maggots attain their 

 growth in from four to seven days and the adults emerge in about 

 10 days. The females must then feed for, generally, eight to 

 fourteen days before they mature their first batch of eggs. This 

 fact is of utmost importance in making plans to get rid of flies. 

 With an effective trap, properly baited and managed, in the stable 

 window or barnyard and outside the kitchen door how many flies 

 would be likely to feed for this length of time without getting 

 caught? If thay all caught themselves, how many flies would 

 we have at the end of two weeks? 



Cost to the Community of Fighting Flies, and cleaning up their 

 filth. Figure for the season cost of foods spoiled by flies, and cost 



