rally only two or three, at times running into one another; posterior wings colourless except at the extreme ends, where they are brownish. A dark spot in the centre of each wing. The Sub-Imago only differs in that the colours are more confused. Spots on abdomen less distinct.

The female Imago is paler in head and thorax, wings much more lightly tinted with a greenish-yellow, the spots on the wing more separated. The posterior wings have the extremities slightly darker than the rest, the centre spot almost indistinct.

The Sub-Imago only differs in its paler colouring.

Eaton, 1883. EPHEMERA VULGATA.-Male Imago.-Head

2

1

EPHEMERA VULGATA.

1, Sub-Imago, male. 2, Female Sub-Imago.

peach-brown; eyes sepia-brown; abdomen pale olivaceous, with pitch-brown markings tinged with ochre at the upper segments and in the middle line of some of the hinder segments; legs olivaceous or olive-brown; setæ and forceps pitch-brown and lutescent; wings pale greenish-grey tinted or yellowish-green, tinted with black nervations, many cross veinlets bordered with pitch-brown; spots on the wing very marked, pitch-brown.

The Sub-Imago.- Wings at first yellowish or greenishgrey, changing to ancreous, broadly tinged with black-grey along the terminal margin; discal spots fuscous, cross veinlet edged with ivory-black.

Female.-Wings paler than the male; sometimes a spot in the middle of the posterior wing.1

From a number of observations made by the river-side by Mr. W. P. Crake and ourselves on the different genera and species of the Ephemerida taken in 1886 and 1887, we found that all these insects, from the time they rose from the surface of the water, remained in the sub-imago state as near as possible forty-eight hours before changing to the imago or perfect insect. In this latter state they lived from six to eight days, and in some of the genera, as Baetes and Cloëon, as long as ten days. Whether they would thus live in a state of nature is doubtful, as some writers observe that probably the act of procreation shortens the lives of most of the Ephemerida, and, therefore, in a free state would not live so long as those kept in confinement.

The mode of transformation from the sub-imago to the imago state is accomplished in the following manner :Somewhere about the forty-eighth hour the insect commences to flutter its wings very rapidly, so much so that the movement could with difficulty be followed. This rapid action continued from thirty to fifty seconds, then ceased, and the wings, previously upright, became perfectly flat and applied close to the body, with a very slight movement of the head and thorax. These parts split open and the perfect insect began to emerge, and rapidly divested itself of its previous covering, the whole process taking about a minute to complete. Sometimes the insect could not get the setæ, which appear folded up, clear of the old covering; and when this occurred it became very excited, fluttering the wings and bending the body backwards and forwards in its endeavours to release itself. The setæ,

short in the sub-imago, become in many species of great length in the perfect state. We found also that the colour of many of these insects varied with their age. For instance, on Wednesday, April 21, 1886, ten olive duns, captured as they left the water, were put into a glass case,

1 We have found the spots in the posterior wings of both male and female, but they are more constant in the male.

and the case exposed to light and sun. In forty-eight hours they began to change as described above. When emerged from the sub-imago to the imago state the abdomen was of a light yellow, the segments lighter still. After some hours the colour darkened, and on the 24th, i.e., in three days, they had all become a dark-reddish, claret-colour, the males a deeper colour than the females. These insects lived eleven days; so that an insect caught immediately after it had assumed its imago state might easily be described as a species different to the same insect caught two or three days after.

In the May-flies proper the same process was observed; the imago or perfect insect bursting its case about the same time and in the same manner.

As regards the change from the nymph to the sub-imago state, amongst the smaller genera it is difficult to detect the exact moment of the change, but with the larger species (May-flies) the nymph rises to the surface, and it is often some little time before it can free itself from its nymphcovering (shuck), floating and fluttering along the surface of the water for a few moments before rising in the air. It is then that its life is so often cut short by the greedy trout.

The rise of the nymph of the May-fly from the bed of the river appears to be very uncertain, and from our observations does not so much depend on the state of the atmosphere as is supposed. Sometimes it would appear in considerable numbers as early as 9.30 A.M. On other days (these observations were made in 1885) it would be much later the temperature of air and water being the same in both instances. The effect of the sun's rays on the hatch was very variable. On one cold blustering day, towards the afternoon, the rise was something extraordinary, swarms of the fly pervading air and water. On another day, with

a warm sun, the hatch was but small.

May-flies remain attached to the under-surface of the leaves both of trees and bushes during the early hours of the day. But generally between two and three o'clock, whatever might be the state of the atmosphere, most of

them left their resting-places and commenced their peculiar up-and-down motions, or dances in the air, the males predominating; and when the females arrived these dances greatly increased in rapidity, the union of the sexes taking place at all hours during these movements. We have often seen as many as six males attached to one female, gradually descending to the surface of the water or the ground before parting asunder, and in one instance we found a male Danica in union with a female Vulgata, with a male Vulgata clinging to the body. It appears to us, from carefully observing numbers of males and females, that in all probability a promiscuous intercourse between the two (so-called) species is not uncommon.

Our observations agree with Mr. Eaton's description of the Ephemera danica, whether it be a distinct species or a variety. We found both species in very considerable numbers, the E. danica being more numerous.

There were certain marks which we found pretty constant. The spots on the anterior wings in the Danica were as a rule five, one being close to the base of the wing. In E. vulgata the spots were usually three, the abdomen always as described by Eaton, the anterior segments being ivory-white.

The spot in the posterior wing absent in Danica, usually present in Vulgata, particularly in the male.

The males of both species much smaller than the females, and appearing a day or two before the females.

The sub-costal nervure, colour of the legs, and setæ varied considerably.

The male May-fly in his perfect state is seldom a prey to fish. He lives, when not resting under leaves, well above the river, dancing in the air, waiting for his wives. The swifts, swallows, chaffinches, and other birds are its enemies at that period of its existence. But when the duties are performed for which he has been brought into existence, in a short time he falls helpless and dies, often floating down the stream, then eagerly taken by the fish, and in that condition known in angling parlance as the spent gnat.

Y

The female, when she throws off her sub-imago state, flies away to find a husband, the two combined falling gradually to the ground, or to the surface of the water; but just before reaching it the male detaches itself and mounts again in the air, while the female proceeds to deposit her eggs on the surface of the water, which sink at once to the bottom of the river. She then has to go through many dangers in her short career; she may be snapped up as she is laying her eggs either by fish or bird, or she may get her wings wet and be unable to rise, and so is hurried away by the stream, utterly helpless, and dies exhausted.

The eggs extrude from the seventh ventral segment in the female, and we observed that she sheds or lays a certain number every time she dips on the surface of the water. We caught them just after dipping, and then found none ready for immediate expulsion; and we caught them after having risen and remained in the air for a few moments, and then found a cluster of eggs half-exuded and ready for expulsion.

The May-fly season of 1887 was characterised by the fly first appearing some days later than is usual, and also in some localities by enormous numbers, which pervaded the streams and adjacent bushes and meadows. Another peculiarity was, that there was no morning hatch, although there was for the most part a bright sun, but the wind was either north-east or east. The fly generally did not hatch till after midday, and then in small quantities, the great hatch taking place from 3.30 or thereabouts, and continued till 8 or 9 P.M. On some afternoons the air appeared full of a dense mist, which was nothing but swarms of Mayflies, and the accumulation of the dead was so great at some of the hatchways and elsewhere as to produce a most nauseous odour.

Mr. Eaton states "that many of the characters upon which the classification of the Ephemerida was formerly based have proved to be unsuitable for the purpose. Originally the number of the caudal seta was deemed a matter of primary importance; and when forms were dis