Nature's Scavengers . 
[April, 
To destroy these pseudo-scavengers— -who in reality, like 
the “ pushing” quacks of whom they are the type, intensify 
the ills which they seem to cure — we must poison their 
pabulum. One of the perils of sewage irrigation is, that it 
gives great facilities for the multiplication of flies in the 
ever-moistened earth. The claims of the mosquito and its 
allies to be regarded as purifiers of the rivers, and of the 
house-fly to rank as the purifier of the air, we shall discuss 
below. Reviewing, then, the charabter of Dipterous dung 
and carrion devourers, we are tempted to ask — What is, 
after all, their especial mission ? Are they adapted to 
remove putrid matter, or to propagate putrefaction and 
disease ? We fear the balance of evidence is in favour of 
the latter view, and that one great class of nature’s scaven- 
gers does more harm than good. The significance of this 
is apparent. But the most remarkable fabt is that these 
pseudo-scavengers, the Diptera, are more successful than the 
genuine perfebt scavengers among the Coleoptera. They are 
ten-fold, perhaps a hundred-fold, more numerous than the 
Silphidse and the Saprophagous Lamellicornes. Instead of 
receding before the advance of civilisation and the increase 
of human population, they seem — like rats, mice, bugs, 
cockroaches, &c. — to grow upon us, and may yet constitute 
a danger more serious than some of us imagine. 
Several Crustaceans will be mentioned among aquatic 
scavengers. The land-crabs, however, of which there are 
several species in warm climates, are given to prey upon 
dead animals. Some of them have been even known to 
devour human bodies which had been negligently buried. 
The snails and slugs, to which we shall have to recur as 
consumers of vegetable refuse, occasionally prey upon dung. 
We have frequently, during entomological rambles in the 
early morning, seen the large common black slug feasting 
heartily upon human excrement. To what other species 
this habit extends we are unable to say, but we commend 
the fabt to the careful consideration of all lovers of 
escargots. 
Vegetable refuse probably contributes as much to the un- 
healthiness of a district as animal substances, being gene- 
rally much more abundant. Its removal is very unequally 
provided for, and is scarcely even attempted by vertebrate 
animals. Decayed and decaying timber is broken up and 
consumed by myriads of insects : in cold climates by the 
larvae of the goat-moth, the wood-leopard, the stag-beetle* 
* We have never known a perfe&Iy sound tree attacked by this fine insedt 
(Luc amis cervus ), and we there ore question the justice of ranking him among 
the enemies of the gardener. 
