1875.) Modern Entomology. 225 
matter that are too small to be appreciated by the larger 
aquatic beings; and by devouring them, purify the water, 
and convert death into life. Even in our ponds at home we 
are much indebted to the gnat larve for saving us from 
miasma; whilst the vast armies of mosquito larve that 
swarm along the edge of tropical lakes, and feed upon the 
decaying substances that fall from the herbage of the banks, 
purify at the same time the water and the atmosphere, and 
enable human beings to breathe with safety the air in which, 
without their aid, no animal higher than a reptile could have 
existed.” 
To this passage, ably written as it is, many exceptions 
may be taken. If man is not to intrude into the “ natural 
domain of the mosquito,” his choice of a dwelling will 
be very limited; since, with the exception of sandy and 
stony deserts, scarcely one-fourth part of the land on our 
globe is free from these pests. We are not sufficiently well 
acquainted with the nature and origin of miasma to decide 
whether the larvz of mosquitos do really purify the water 
and the atmosphere. That they feed upon particles of 
putrescent or putrescible organic matter in the waters is very 
probable; but will not, in that case, their excrements and 
their dead bodies be as great a nuisance as their original 
pabulum? They are found in pestilential districts, which 
proves that their services in a sanitary point of view are at 
least questionable. They swarm also in regions free from 
malaria, and where its existence seems highly improbable, 
such as Lapland. ‘They are known also to be spreading into 
parts hitherto free from them, and where no malaria had 
been met with in their absence. How is it that teleologists 
judge the ‘‘ contrivances of Nature ’’ so much more leniently 
than those of Art? What would they say, for instance, of a 
city where the scavengers and nightmen were employed 
occasionally as surgeons, hospital nurses, and provision 
dealers, so that they might distribute putrescent and 
infectious matter upon the food, the medecines, and the 
very persons of the inhabitants? Yet such a case would be 
precisely similar to that of some of Nature’s scavengers—to 
wit, the common house-fly and its allies. These are one 
moment feasting upon carrion, excrement, and ulcers; and 
the next, settling upon food, and upon men and animals. 
That in this manner they are active propagators of disease 
is no mere supposition. Which, then, is the real function of 
the fly, scavenging or the spread of disease? We have no 
more right to assume the one than the other. Surely our 
