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Rural School Leaflet 



horse manure, but if this is not available she will lay the eggs on almost 

 any kind of manure. She usually places them in horse manure because 

 it is the favorite food of the larva, the form of the insect that emerges 

 from the egg. The eggs (Fig. i, b) are minute, whitish objects, about 

 one twentieth of an inch in length, shaped like a grain of wheat. Each 

 female may lay four or five lots of eggs, each lot containing ioo to 150 

 eggs, or a total of 400 to 600 eggs. It requires eight to twenty-four 

 hours, depending on the temperature, for the insect to complete its growth 

 in the egg. 



The small larva (Fig. 1, c) that issues from the egg through the 



broken eggshell is footless, is 

 about as long as the egg, and 

 is known as a maggot. It 

 is during the larval period 

 that the insect feeds and 

 stores up fat to sustain it 

 during its later life. At the 

 end of a period of five to 

 seven days the larva is fully 

 grown and has molted its skin 

 three times. The body is now 

 Fig. 1. — House-fly: (ft) adult; (b) eggs; (c) larva, about one third of an inch 

 HowaX'' ^ ^^"^ AU enlarged ' {From long, pointed at the head end 



and blunt at the other end. 

 When the larva is fully grown it stops feeding. The body becomes 

 much contracted or shortened, and barrel-shaped. The outer larval 

 skin is dried, wrinkled, hard, and brown in color. The insect shrinks 

 away from this brown skin, becomes entirely free from it, and uses this 

 skin merely as a shell to protect it during the striking changes that it must 

 now undergo. The shell is the puparium (Fig. 1, d). The short-bodied 

 insect enclosed in the puparium is the quiescent pupa. The pupa does 

 not take any food. It is during this stage that the legs and the wings 

 are formed. Five to seven. days are required for the transformation of 

 the pupa into a fully formed fly (Fig. 1, a). When this time is reached, 

 the pupal skin is molted, freeing the fly, which breaks off the head end 

 of the puparium, escapes from it and from the pile of manure, and begins 

 its life as a winged insect. 



If the time required for each of the life periods given above be added 

 together, it will be found that ten to fifteen days are required for the 

 complete development of a house-fly. This makes it possible for the 

 production of six to eight generations of flies during the warm months 

 from June to September. The mortality among insects is always high, 



