54 THE BEAUTIES OF NATURE CHAP. 
mann has proved by actual experiment. He 
put one of these caterpillars in a tray, in 
which he was accustomed to place seed for 
birds. Soon a little flock of sparrows and 
other small birds assembled to feed as usual. 
One of them lit on the edge of this tray, and _ 
was just going to hop in, when she spied the 
caterpillar. Immediately she began bobbing 
her head up and down in the odd way which 
some small birds have, but was afraid to go 
nearer. Another joined her and then another, 
until at last there was a little company of ten 
or twelve birds all looking on in astonishment, - 
but not one ventured into the tray; while 
one bird, which lit in it unsuspectingly, beat a 
hasty retreat in evident alarm as soon as she 
perceived the caterpillar. After waiting for 
some time, Weismann removed it, when the 
birds soon attacked the seeds. Other cater- 
pillars also are probably protected by their 
curious resemblance to spotted snakes. One 
of the large Indian caterpillars has even ac- 
quired the power of hissing. 
Among perfect insects many resemble closely 
the substances. near which they live. Some 
