84 THE HOUSE FLY—DISEASE CARRIER 
able whether it would attack any animal or insect larger 
than itself. Marlatt states that if pressed with the 
bare foot or hand, or if caught between sheets in beds, 
it will unquestionably bite in self-defense. He also 
shows that the few such cases on record indicate that 
severe swelling and pain may result from the poisonous 
injection. Prompt application of ammonia, however, 
will alleviate the symptoms. 
No one knows much about the life history of this 
creature. Full-grown specimens are found in houses 
all through the year; half-grown individuals are some¬ 
times found in the summer; the youngest ones known 
differ from the older ones chiefly in having fewer legs. 
It is interesting to note that a careful look at the hind 
segments of the young will show the long posterior 
legs folded up within and ready to be extended after 
the next molt. 
Under present conditions of house fly abundance, it 
might be as well not to disturb this Scutigera when 
it is found in houses, but with the conditions which 
will shortly be brought about, we hope, it will be easy 
to destroy the centipedes with pyrethrum powder, even 
if they do not, as is likely, die of starvation. 
Insect Enemies of the House Fly 
Predatory enemies .—It seems rather strange that, 
with the very numerous predaceous insects which de¬ 
rive their sustenance from soft-bodied and more or less 
helpless species, there should not be more which gain 
their livelihood from the larvae of the typhoid fly. It 
