Ir THE SERVICE OF TAILS 81 
the same observation may prove true of winged 
insects having hinder appendages or prolonged 
abdomens, such as dragon-flies. “ Short-tailed 
birds,” remarks Frank M. Chapman, “generally 
fly in a straight course, and cannot make sharp 
turns, while long-tailed birds can pursue a most 
erratic course with marvellous ease and grace. 
The grebes are practically tailless, and their flight 
is comparatively direct, but the swallow-tailed kite, 
with a tail a foot or more in length, can dash to 
right or left at the most abrupt angle.” 
Many a wild creature trusts to its tail for defence 
in time of danger, and finds in it an offensive as 
well as a defensive weapon of no mean worth. The 
“fighting formation” of the American porcupine, 
for instance,! is to turn its back on its foe, hide its 
head beneath its thorny neck, and strike right and 
left with its short, spade-shaped tail: this organ 
is armed with the longest and strongest spines, 
and it is astonishing what a quick, forcible, and 
effective blow the little animal can thus deliver. 
It is probable that the heavy, knobbed tail of 
the gigantic Mesozoic glyptodon was similarly 
used. Whales will stave a boat to pieces by 
a stroke with their powerful flukes; and the 
“thresher” shark takes his name from his habit 
of swinging violently back and forth the long 
scythe-like prolongation of the upper half of his 
tail-fin. It is said that he kills small fishes for his 
1 See also Chapter VII, page 188. 
