THE EPHEMERID, OR MAY-FLIES. 289 
The female, with her ovaries full of eggs, is the insect that the 
fish prefers; and the wise angler tries to delude his victim with a 
seductive imitation, which he calls a “Grey Drake.” His “ Green 
Drake” is the female subimago, and the “ Bastard Drake” the 
male subimago. All these belong to Lphemera danica. ‘The 
“dun flies” of the angler are mostly Ephemeridee in the subimago 
state. 
The larve and nymphe are provided with longer antennz 
and shorter tails than the imagines. The mouth is well developed, 
and consists of a pair of mandibles, sometimes prolonged into 
frontal horns, a pair of maxillz, with palpi of two or three joints, a 
labrum, and a labium, with labial palpi. Their food consists of 
diatoms and other protophytes, mixed with mud; occasionally 
with protozoa, and in some genera entomostraca, and even minute 
larvee, in addition. They either swim or crawl among water-plants 
Fig. 59. Fig. 60. 
Nymph of Ephemera, Nymph of Cloeon. 
or hide under stones. Some genera, however, form horizontal 
burrows in the mud, in which they find warmth during the winter 
and security during repose, and from which they sally forth only in 
quest of food. 
All the British genera have external branchie, usually consisting 
of a pair of single or double plates to each of the first seven 
segments of the abdomen. These gills are lance-shaped, leaf- 
shaped, oval, or divided into threads. They are sometimes 
provided with a fringe of membranous threads round the margin, 
as in Ephemera. (Fig. 59.) Heptagenia, which frequents very cold 
streams and the rapids of rivers, has seven leaf-shaped gills on each 
side, each with a bundle of threads attached to its root, the analogue 
