THE EPHEMERID#, OR MAY-FLIES. 287 
ing the wings, and which gives them a dull appearance. In this 
state, which is called variously by the names fro-cmago, pseudimago. 
or subimago, they fly or crawl to the nearest resting place, to divest 
themselves of this garment; and anglers have related that, as they 
sat upon the banks of some stream, on a quiet summer evening, 
they have found the rims of their hats covered with these “fairy- 
like” skins of the subimago. It is often asserted that the casting 
of this additional skin is peculiar to the Ephemeride. This is 
doubtless a mistake; for Newman, Westwood, and others have 
observed the Dragon-fly and other insects quit a double-skin on 
attaining the perfect state ; but the subimago skin of the May-fly is 
retained longer than that of other insects, 
These insects, however, undergo no true metamorphosis, in the 
ordinary acceptation of that term. They are born with six legs, 
two antennee, and two tails, and almost all the changes they undergo 
during growth are developmental. ‘The nymph gradually acquires 
wing-cases, which it uses for purposes of respiration in the water, 
and is similar in all other respects to the larva that has no wing- 
cases. When the nymph becomes a subimago, it leaves its long 
antennee, jaws, and abdominal gills, and sometimes its middle tail, 
behind it, with its cast skin, and we find in their place short 
antennee, an aborted mouth, and spiracles; but equally important 
changes take place during the growth of the larva, when it is not 
supposed to be passing through metamorphosis, and it might be 
more properly described as undergoing mw/tiple metamorphosis, 
inasmuch as a change of structure is apparent after every moult. 
Growth and development visibly take place at the same time. 
There is no inactive state analogous to that of the pupa of the 
Lepidoptera ; the quiescence of that order of insects being neces- 
sary on account of their inability to take food during the change ot 
the mandibulate mouth of the caterpillar into the suctorial mouth 
of the butterfly. 
Although the Ephemeridz pass so eran a portion of their lives 
in the air, their life-history upon the wing is one of considerable 
interest. The alimentary canal is straight and inflated with gas, 
which renders these insects very light, and in some genera their 
soft and feeble muscles render them incapable of strong flight, so 
that they are often blown about by the wind. In some localities, 
when atmospheric conditions have been more than usually favour- 
able for their leaving the water, clouds of these insects may be 
seen hovering in the air, each seeking the final object of its exist- 
ence, the perpetuation ‘of the species. Their dead bodies have 
sometimes been found so thickly upon the ground in some parts of 
Italy, that they have been carted away and used as manure. 
Swammerdam, the Dutch naturalist, who was the first to investigate 
with accuracy the anatomy of a May-fly, described a species that 
