1876.] Nature's Scavengers . 161 
excess of matter more than can be consumed by the larvae. 
Nor is the mischief of putrefaction merely deferred or altered 
in form, as in the case of many carrion-feeders, since the 
excrements of the larvae are absorbed by the earth, as well 
as the gases and vapours resulting from the decomposition 
of the dead body. 
Before we pronounce any scavenger perfect we must be 
sure that he confines himself solely to his useful, though 
repulsive task, and does not go about bedaubed with filth, 
disseminating the seeds of putrefaction, and probably of 
disease. Tried by this test the sexton-beetle is justified. 
He does not intrude into our dwellings, settle on our food, 
and buzz about our persons, contaminating whatsoever he 
touches. He removes, without propagating, nuisance, and 
the removal is not attended with any drawback or set-off. 
We must therefore declare him an admirable, unimpeachable 
scavenger, wishing him every success in his operations, and 
full immunity from the competition of quacks and bunglers. 
But with all these good qualities — perhaps we must even 
say because of them — he barely holds his ov/n in the struggle 
for existence, and seems to us to be decidedly decreasing in 
numbers. An animal which feeds on one kind of food only 
is naturally at a disadvantage if it has to compete for the 
means of existence against omnivorous species. The Necro- 
phorus , feeding only on carrion, is “ underbidden ” by crea- 
tures which can feed upon almost any kind of organic 
matter, and which are perfectly ready to deposit their ova 
in fresh flesh if they can find nothing already tainted. This 
is, we submit, a crucial case, deciding the comparative 
merits of the new and of the old natural history, and as 
such we shall have to refer to it again. No less does it 
exclude certain applications of the doCtrine of “ Natural 
Selection ” made by political economists. We have still to 
notice the extreme limitation of the burying propensity. 
The other genera of the Silphidse, though preying upon 
carrion* and depositing their eggs in the same material, do 
not bury, and are consequently of much less value as re- 
movers of nuisances. Now, if the burying propensity be an 
instinCt especially implanted in these inseCts in order to 
preserve the air from taint, why is it restricted to one small 
group — neither rich in species nor in individuals — among an 
extensive family of carrion-feeders ? Might we not rather 
* Some of the species of Silpha attack living prey. MacLeay states that 
Silpha 4 - punctata ascends oaks in pursuit of caterpillars. We have captured 
it on oaks in Dunham Park, near Manchester, under circumstances which 
decidedly favour this view. 
VOL. VI. (N.S.) 
X 
