EPHEMER1M. 
139 
air from the water; these are situated on the abdomen and 
consist of thin walled processes in which the body fluid circulates 
and in which tracheae are found. In fact, the 
gills supply the tracheae with air and are not gills in 
the same sense as in fishes. The form of these 
nymphs in general is very varied, as are their 
habits and there will probably be found a similar 
variety in Indian species. The reader will find 
general information in Miall’s Aquatic Insects, 
in Sharps’ Insects and in Eaton’s Monograph. 
A curious feature of the life-history is the 
very sudden transformation ; the full-grown nymph 
comes to the surface, the skin breaks along the 
back, the flying insect emerges; but its meta- 
11 larva, P Ceylon NIA morphosis is then not really complete and the 
[After Eaton,) insect (now called a sub-imago) flies to a spot on 
which to settle, then sheds another delicate skin. This phenomenon is 
known only in this family. One species common in the plains flies some 
hundreds of yards before doing this and comes to light, settles on the 
wall and then emerges fully developed, leaving the delicate skin behind. 
The nymphal life is probably as long relatively as the imaginal life 
is short. The May-flies are types of the brevity of life, but in reality 
these insects have previously enjoyed a very long life (for an insect) in 
their aquatic form. Lubbock found that the nymph of a European 
species underwent twenty moults. The perfect insects apparently emerge 
to a brief career of enjoyment. May-fly dances are a common feature of 
a still warm evening, the delicate insects (males) performing intricate 
evolutions in companies on the wing. A dance in three dimensions may 
have advantages over the dance on the two dimension dance-floor and 
we can compare it only to a dance of flying machines. These dances 
take place often at a considerable distance from water, a number of the 
insects gathering together for the purpose and forming a very striking 
sight. Coupling and egg-laying closes the brief life. As the mouthparts 
are absent and no food is taken after emergence, an active life must soon 
close, and it is probably correct to say that May-flies do not live for 
more than one or a few days. The immense swarms of May-flies that 
emerge simultaneously in some countries do not seem common among 
