National Geographic : 1910 May
Photo by N. A. Cobb Copyright, 19io, by the National Geographic Magazine FEMALE HOUSE-FLY RESTING ON GLASS AND SEEN FROM ABOVE The house-fly swallows many kinds of germs and spores, and deposits them all day long at intervals of a few minutes in its excreta, the "fly specks." Th.ese germs and spores pass through the fly in less than an hour, and come out in the fly specks alive and uninjured. Flies spread more germs in this way than in any other. The house-fly sticks close to man and is a dangerous agent in the spread of human diseases. Diseases of animals and plants are spread in the same way. The hairs on the back of a fly are not a haphazard arrangement, but correspond in number and location on all house-flies.