8 o 
Dragon-flies and Damsel-flies 
as well as forward, and by a special sort of articulation of the head on the 
thorax it can be rotated readily through i8o°, so that the principal part of 
each eye can be directed sidewise or even straight down. For accurate 
flight and successful pursuit of flying prey the dragon-fly has full need of 
good eyes. It is to be noted, too, that the eyes are relatively largest in those 
particular dragon-fly kinds which have the most powerful flight. On the 
head, also, are three simple eyes (ocelli), the pair of very small awl-like 
antennse, and the great mouth. The mouth is overhung as by a curtain 
by the large flap-like upper lip (labrum). The jaws (mandibles) are strong 
and toothed, and obviously well adapted for tearing and crushing the cap¬ 
tured prey. 
When the prey is come up with, however, it is caught not by the mouth 
but by the “ leg-basket.” The thorax is so modified, and the insertion of 
the legs such, that all the legs are brought close together and far forward, 
so that they can be clasped together like six slender, spiny grasping arms 
just below the head. Although the catching and eating is all done in the 
air and very quickly, observers have been able to see that the prey is caught 
in this ‘ £ leg-basket ” and then held in the fore legs while being bitten and 
devoured. These slender legs are used only very slightly for locomotion, 
but they serve well for the light unstable perching which is characteristic 
of the dragon-flies. 
The internal anatomy is specially characterized, as might well be 
imagined, by a finely developed system of thoracic muscles for the rapid 
and powerful motion of the wings and the delicate and accurate move¬ 
ments of the legs. The respiratory system is also unusually well developed, 
such active insects needing a large quantity of oxygen, and generating a 
large amount of carbon dioxide. The respiratory movements, according 
to Calvert, consist in an alternate expansion (inspiration through the ten 
pairs of breathing-holes, or spiracles, arranged segmentally on thorax and 
abdomen) and contraction (expiration) of the abdomen. The rate of 
movement varies greatly at different times owing to unknown causes, but 
is always quickened by exercise, increased temperature, or mechanical irri¬ 
tation. In different dragon-flies the inspirations have been noted to be 
from 73 to 118 a minute. 
The dragon-flies are famous for their beautiful metallic colors. As they 
dart through the air one gets glimpses of iridescent blue and green and cop¬ 
per, of tawny red and violet and purple reflections that are most fascinating 
and tantalizing. Seen close at hand in the collections, however, they are 
mostly dull-colored and, except for their “pictured” wings and the sym¬ 
metry and trim outline of their body, rather unattractive “specimens.” But 
a freshly caught dragon-fly shows the real glory of the coloring: delicate 
changing shades of green and violet and copper quiver in the great eyes; 
