FIELD ZOOLOGY. 



their feet. There should be as determined a crusade 

 against the house fly as there is now being carried on 

 against the mosquitoes. House flies are responsible for 

 the spread of Asiatic cholera, typhoid fever, tuberculosis, 

 and it may be proved that they have much to do with 

 the carrying of diphtheria. (Fig. 80.) 



The eggs of the house fly are laid in manure piles 

 usually, or in some other decaying matter of even a more 



FIG. 79. Foot of a house fly. 

 (Kellogg.} 



FIG. 80. A house fly. 

 (Kellogg.) 



repulsive nature. Each female lays about one hundred 

 eggs. These eggs hatch in about six or seven hours, 

 and the larvae lie in the midst of abundant food supply 

 for the five or six days of their larval existence; while in 

 this stage they are minute whitish grubs, pointed at one 

 end. The pupal stage lasts five days after this, and 

 during this stage the fly looks very much like a brown 

 seed. After the expiration of these five days the adult 

 house fly emerges to go about houses to carry on the 

 scavenger work and filth-carrying of its parents. Of 

 course it is the juices of the compost heap that render it 

 an attractive place for the fly to lay its eggs; and if that 

 compost were spread upon the land to enrich it (as it 



