INJURIOUS INSECTS OF I909Q AND IQIO. 79 
feels the sharp sting caused by the insect’s biting or stabbing, he 
should realize that this is a stable fly, and not the house fly. Fur- 
thermore, when big flies and little flies are observed upon a window 
pane, the little flies are not to be regarded as the young of the big 
flies, but belong to different species, since flies and other insects never 
grow when they are in the final or perfect state. 
Fig. 30. Petri dish containing agar over which a 
Fly, caught on the experiment station grounds, was 
allowed to walk. The white spots are colonies of bac- 
teria coming from germs left by the Fly when crawling 
over the jelly. Original. 
When we consider the filthy location of the eggs of the house 
fly and know its food, it is no wonder that we turn with disgust 
from any dining-room table where these creatures are in evidence, 
and we are not surprised that, after crawling over such filth, or over 
the saliva of a consumptive, they can and do carry the germs of 
typhoid and tuberculosis. 
It is a matter for congratulation that the housekeepers of Min- 
nesota are keenly alive to the desirability of keeping flies out of 
their houses. One occasionally finds a kitchen infested, or a dining- 
room infested, but as a rule our houses are well protected in this 
particular. It would seem, from facts in our possession, that to 
allow house flies to enter a dwelling-house or a hotel, amounts to 
almost criminal negligence. 
