248 
NATURE’S CRAFTSMEN 
number of dragon-flies is rapidly diminishing the 
world over, because of the drainage of their 
breeding places. 
“ The dragon-fly has proved, in the past, a 
very great friend to man. I wonder if any of 
you can guess how? ” 
“ I wonder if you mean that he kills mosqui¬ 
toes? ” asked Tommy. “ I have seen him chas¬ 
ing them many a time.” 
“ Right. Countless millions of these little 
blood-suckers have been slaughtered by the vigi¬ 
lant policemen of the air—to our own comfort.” 
