EEV. A. E. EATON ON EECENT EPHEMERID^ OR MAYFLIES. 9 



portions of it as may be shed are moulted while the insect is in full flight. Thus the 

 males of Oligoneurla retain the pellicle in question u.pon their wings (the slough that 

 may often he seen still dangling from their tails comprises exuviae of the body, legs, and 

 setae only), whilst the females of Palu?ffenla, Campsurus, and some others, seem to throw 

 off none of it at all. The males of these restless creatures have their hinder legs either 

 atrophied or too feeble to support the body, and in most of the females the fore legs also 

 are equally infirm and functionless. The longer-lived flies issue from the nymph-skin in 

 a rather less matured condition than the others : then' legs are alwavs serviceable in both 

 of the sexes ; and the subimago skin is always completely cast. The change from nymph 

 to subimago is effected while the insect is floating at the surface of the water, buoyed up by 

 gas which has accumulated wdthin the alimentary canal and between the new and the old 

 integuments of the body. The moult having been transacted in the ordinary manner, the 

 subimago, standing upon the water with the wings erect, awaits a favourable moment for 

 flying to shelter. Fluttering steadily upwards it mounts aloft, sometimes to a considerable 

 elevation, presently making its way to trees, walls, or herbage, &c., likely to afford it a 

 suitable resting-place. There it assumes the posture characteristic of its genus during 

 repose. It uiay stand either upon all of its feet, or upon only the two hinder pairs ; and 

 the fore legs extended in advance, off the ground, may in this last case be held either 

 close together or else apart from each other. The caudal setaj, in most instances diver- 

 gent, are sometimes placed alongside of one another horizontally, or slanting upwards. 



Adult diurnal Ephemeridre, in hot weather, seek repose during the heat of the day, 

 limiting their flight to the cooler hours of sunlight, or, at most, extending it later in the 

 evening till just after sunset. In cold disagreeable weather they seldom fly at all, but 

 remain under shelter. Many persons are familiar with the mode of flying habitual to 

 some of the more conspicuous Mayflies (especially the males), which, by tlie intermittent 

 action of the wings, results in a dance-like motion almost vertically up and down, — a 

 fluttering swift ascent, and tlien a passive leisurely fall, many times repeated. The body 

 during the rise is carried in a position very little out of the perpendicular, with the legs 

 extended upwards in advance, and the setas trailed behind; and this is thepostm-e main- 

 tained by Septa rjenia and its allies (only their sette are divergent) whilst hovering head to 

 windward, which has led to their being locally designated in the valley of the Axe (Devon) 

 "Yellow Uprights." During the descent, the body, less steeply inclined, is steadied by 

 the half-spread motionless wings and the outstretched setae and legs. The males of Ccenis 

 sometimes jerk themselves downwards impetuously in their dance, instead of subsiding 

 without effort ; and the females of Ephemerella, while flying horizontally onwards, have 

 a haliit of dipping frequently in their flight. Conspicuous objects near water, such as 

 roads, hedges, and shrubs, as well as the streams inhabited by the nymphs, are favourite 

 rendezvous of the dancers, and therefore good sites for collecting the adult flies. In 

 mountain-glens and wooded ravines prominent light-coloured rocks often serve to attract 

 them ; but frequently in such situations their diversions proceed beyond the range of the 

 net. When this is so, it is advisable to watch for subimagines rising frona the water, and 

 carry them home alive in bottles, to undergo their moult. The bottles must be kept cool, 

 and neither very dry inside nor visibly damp ; and it is sometimes necessary to place 



SECOND SERIES. — ZOOLOGY, VOL. III. 2 



