426 
SAVAGE SUDAN 
The Clean Slate. 
So far, not one single large and active animal of Africa 
(or elsewhere) has found place upon our slate. There is merely 
inscribed upon an insignificant corner thereof the names of 
that inchoate and mostly invertebrate crowd of lowly insects 
and reptiles whose immobile lives are spent restricted within 
narrowest limits. And let me repeat that, even for these, it is 
not COLOUR which constitutes their main protection, but chiefly 
their rigid immobility—-sometimes combined with mimicry and 
with “shamming dead.” 
The Green Caterpillar. 
That green caterpillar upon a green leaf is a type writ large 
in this gallery. He seems to symbolise the whole theory. 
But are you sure ?—even about him ? Spend a mid-summer’s 
morn in quiet observation among the woods—plant your deck¬ 
chair in some shady nook beneath the lush foliage of July, and 
you may soon begin to doubt the bona fides of even your green 
caterpillar. Not for long will you lack evidence that within 
the radius of a stone’s-throw from your retreat there are breed¬ 
ing, say a dozen pairs of blackcaps, garden-warblers, white- 
throats, willow-wrens, robins, each responsible for a hungry 
brood of four, six, or eight fledglings, the whole callow crowd 
all clamouring for just such delicacies as the green caterpillar. 
Each tree overhead, you observe, is a “preserved covert,” beaten 
thrice an hour; every bush and branch is searched ; each leaf 
scrutinised separately, above and below, and by eyes that know 
what they seek. That green caterpillar is bound to be caught 
be he never so green. His colour, after all, offers but scant 
“ protection ” from keen and persistent eyes trained to his 
undoing, and searching within a handbreadth of his refuge a 
dozen times a day? How then does he escape? Not because 
he is green ; but because the supply exceeds the demand, and 
multitudinous survivors number enough and to spare to stock 
the world. Still, by all means, retain the green caterpillar on 
the slate ; for he is a thoroughly typical example of the great 
“ Principle of Colour-Protection.” 
In conclusion, let me place in apposition two examples 
