Mosquitoes and Parasite Problems. 137 
with a pertinacious cloud of gnats or sandflies 
hovering just above my head and keeping me 
company for miles, I have always devoutly wished 
for a stray dragon-fly to show himself. Frequently 
the wish has been fulfilled, the dragon-fly, appa- 
rently ‘ sagacious of his quarry from afar,” sweeping 
straight at his prey, and instantly, as if by miracle, 
the stinging rain has ceased and the noxious cloud 
vanished from overhead, to be re-formed no more. 
This has always seemed very extraordinary to me; 
for in other matters gnats do not appear to possess 
even that proverbial small dose of intellect for which 
we give most insects credit. Before the advent of 
the dragon-fly it has perhaps happened that I have 
been vigorously striking at them, making it very 
unpleasant for them, and also killing and disabling 
many hundreds—a larger number than the most 
voracious dragon-fly could devour in the course of 
a whole day ; and yet, after brushing and beating 
them off until my arms have ached with the exer- 
tion, they have continued to rush blindly on their 
fate, exhibiting not the faintest symptom of fear. 
T suppose that for centuries mosquitoes have, in this 
way, been brushed and beaten away with hands and 
with tails, without learning caution ; it is not within 
their knowledge that there are hands and tails. <A 
large animal is simply a field on which they con- 
fidently settle to feed, sounding shrill flourishes on 
their little trumpets to show how fearless they are. 
But the dragon-fly is very ancient on the earth, and 
if, during the Devonian epoch, when it existed, it 
preyed on some blood-sucking insect from which 
our Culicidze have come, then these stupid little 
