VIEWS OF ERASMUS DARWIN 2 
bo 
I 
the means of escaping other animals more powerful 
than themselves.* Hence some animals have acquired 
wings instead of legs, as the smaller birds, for pur- 
poses of escape. Others, great length of fin or of 
membrane, as the flying-fish and the bat. Others 
have acquired hard or armed shells, as the tortoise 
and the Echinus marinus (p. 239). 
“The colors of insects,” he'says,“ and many smaller 
animals contribute to conceal them from the dangers 
which prey upon them. Caterpillars which feed on 
leaves are generally green; earthworms the color of 
the earth which they inhabit; butterflies, which fre- 
quent flowers, are colored like them; small birds 
which frequent hedges have greenish backs like the 
leaves, and light-colored bellies like the sky, and are 
hence less visible to the hawk, who passes under them 
or over them. Those birds which are much amongst 
flowers, as the goldfinch (/r7ngzlla carduelis), are fe 
nished with vivid colors. The lark, partridge, hare, 
are the color of dry vegetables or earth on which 
they rest. And frogs vary their color with the mud 
of the streams which they frequent ; and those which 
live on trees are green. Fish, which are generally 
suspended in water, and swallows, which are generally 
suspended in air, have their backs the color of the 
distant ground, and their bellies of the sky. In the 
colder climates many of these become white during 
the existence of the snows. Hence there is apparent 
design in the colors of animals, whilst those of vege- 
* The subject of protective mimicry is more explicitly ste ated e 
Dr. Darwin in his earlier book, Zhe Loves of the Plants, and, 
Krause states, though Résel von Rosenhof in his /rsehkten- pepe 
gungen (Nurnberg, 1746) describes the resemblance which geo- 
metric caterpillars, and also certain moths when in repose, present to 
dry twigs, and thus conceal themselves, ‘‘this group of phenomena 
seems to have been first regarded from a more general point of view 
by Dr. Darwin.” 
