192 _ INSECTA. 
four compound eyes, two of which are elevated and much larger than 
the others, called from their form turban’d or columnar eyes. The 
junction having been effected, the couples place themselves on trees 
or plants to complete their coitus, which lasts but fora moment. The 
female soon after deposits all her eggs in the water, collected in a 
bundle. 
The propagation of their species is the only function these ani- 
mals have to fulfil, for they take no nourishment, and frequently die 
on the day of their metamorphosis, or even within a few hours after 
that event. Those which fall into the water become food for Fishes, 
and are styled Manna by fishermen. 
If however we trace them back to that period in which they existed. 
as larvee, we find their career to be much longer, extending from two 
to three years. In this state, as well as that of semi-nymphs, they live 
in water, frequently concealed, at least during the day, in the mud or 
under stones, sometimes in horizontal holes divided interiorly into 
two united canals, each with its proper opening. These habitations 
are always excavated in clay, bathed by water, which occupies its ca- 
vities; it is even supposed that the larve feed on this earth. 
Although allied to the perfect Insect, when it has undergone its 
ultimate metamorphosis, in some respects they differ. The antenne 
are longer; the ocelli are wanting ; and the mouth presents two projec- 
tions resembling horns, which are considered as mandibles. On each 
side of the abdomen is a range of laminz or leaflets, usually united 
at base by pairs, which are a sort of pseudo-branchie over which the 
trachez extend and ramify, and which not only enable them to re- 
spire but also to swim and move with greater facility; the tarsi have 
but one hook on their extremity. The posterior extremity of the 
body is terminated by the same number of sete as that of the perfect 
Insect. 
The seminymph only differs from the larva in the presence of the 
cases which enclose the wings. When the moment of their develop- 
ment has afrived, it leaves the water, and having changed its skin, 
appears under a new form—but, by a very singular exception, it has 
still to experience a second change of tegument, before it is prepared 
to propagate its species. The ultimate exuvium of these Insects is 
frequently found on trees and walls; they sometimes even leave 
them on the clothes of persons who may be walking in their vicinity. 
With this genus and thatcf the Phryganez, De Geer formed an 
order founded on the absence or extreme exiguity of the mandibles. 
In the * Tableau Elémentaire de |’ Histoire Naturelle des Animaux” 
of the Baron Cuvier, they also constitute a separate family, that of 
the Agnathes, but still forming part of the order of the Neuroptera. 
The number of wings and that of the filaments of the tail furnish 
the means of dividing the genus of the Ephemere. ~ 
E. Swammerdiana, Lat.; E. longicauda, Oliv., Swamm., 
Bib., Nat., I], xii. 6, 8. The largest species known; four 
wings; two filaments to the tail twice or.thrice the length of 
the body, which is of a russet-yellow; eyes black. Holland and 
Germany, along the great rivers. 
