INSECTA. 423 
Sub-genera: Lestes, Calepteryx, Agrion Leacu, Mecistogaster 
Ramevr, and some others of this author, 1.1 p. 217. 
Family XXXII. Ephemerine. Parts of mouth soft. Antenne 
very short, subulate, triarticulate. Tarsi quinquearticulate, with 
first joint mostly very short, scarcely distinguishable. Posterior 
wings less than anterior, sometimes none. Abdomen terminated by 
two or three filaments. 
Ephemera Li, (Characters of the family.) 
May-lies, bank-bait. The larvee and nymphs live at the bottom 
of the water between stones, or in the ooze; some dig horizontal 
passages, in which they move very rapidly. In these two states 
they live two or three years before changing into perfect insects ; 
they proceed from very small eggs. The larva has always three 
threads at the abdomen, of which the middle one in many species 
disappears after the metamorphosis ; it is distinguished especially 
from the perfect insect by longer antenne, by stronger upper jaws, 
and by external respiratory organs at the first six rings of the abdo- 
men ; the air-tubes appear as free threads or little plumes, or are 
united by membrane to form a foliated lamina. Some larve have 
on each side of every ring two such plates. The change from 
nymph to perfect insect occurs in Ephemera Swammerdamii (Palin- 
genia longicauda Bur.) so suddenly that there is almost at the 
same moment a creeping and a flying creature. In other species, as 
in those observed by Rasen, the change takes place more slowly. 
They moult once again in their perfect condition ; and if we be 
walking by the banks of the water over which they are flying we 
often see this moulting performed on our clothes. 
In the middle of summer the May-Fly takes wing towards even- 
ing. The time of flight differs in different species. That which 
SwWAMMERDAM described shews itself nearly three days in succession, 
about St John’s day, in the month of May, and often in such quan- 
tities that it is as difficult to count these little creatures as falling 
snow-flakes. A great many fall into the water a prey to fishes, and 
at that time, especially at Dordrecht, the roach is noted as being 
peculiarly fat and good. Hence the name bank-bait, oeveraas (in 
some parts of France la manne). According to the relation of 
Scoroti they are collected by the country-people in Carniola to 
manure the land (Zntomel. Carniol. p. 264). 
