120 
ZOOLOGY, 
diers^ the latter with large heads and long jaws. The white 
ants in Africa build conical hills six feet or more in height. 
Order 5. OdoiiaUi. — Dragon-flies (Figs. 146^ 147) rep- 
resent this order. They have broad, net-veined wings and 
free biting mouth-parts. The metamorphosis is incomplete, 
the pupae (Fig. 148) being active and feeding on smaller 
insects, only differing from the larvae in having rudiments 
Fig. 148.— Pupa of a Dragon-fly Fig. 149.— May-fly and larva, the latter 
{Mschna). enlarged. 
of wings. Dragon-flies are constantly on the wing in 
pursuit of insects; they are sometimes called ^''mosquito 
hawks. 
Order 6. Plectoptera, — May-flies (Fig. 149) are so called 
from their shortness of life, as they live but a day or two. 
The young live in the water, and breathe by feathery gills 
on the side of the body. 
