458 THE ZOOLOGIST. 
out, but frequently are so in descent, and may act in much the 
same way as a parachute breaking the insect’s fall.* 
The flight of Mayflies is extremely pretty to watch. They 
rise and fall in regular rhythm. Hphemera vulgata looks very 
dark in flight; it either rises and falls or else flies straight away 
very swiftly, and often very high. EH. danica looks reddish in 
flight, and flies if anything swifter than the last, but low, and 
never, according to my observations, very high. This species 
frequents swift-running streams. LH. vulgata generally appears 
with due regularity the first week in June, and I have seen 
species of Mayflies from then through every month up till the 
first week in October. One quite small species, only slightly 
larger than a gnat, which unfortunately I was unable to identify, 
I found in swarms by Frensham great pond in South-west 
Surrey. This had a soaring flight, and often flew very high. 
It hardly appeared to move the wings at all. Numbers of these 
small flies settled on me, and left their pseudo-imaginal skins on 
my coat. Curiously enough, some time after this I happened to 
read in Miall’s ‘ Aquatic Insects’ the following passage :—‘‘ I 
saw in the evening a great crowd of small flies a little larger 
than gnats. So many settled on my clothes that I was com- 
pletely covered with them, and great numbers left their thin 
pellicles behind on my clothes.” 
When the fly of Ephemera vulgata is examined microscopically 
- some remarkable features present themselves. One is at once 
struck with the square appearance of the network of the wings, 
some of the veins forming almost perfect squares. On the outer 
nervure of the fore wing is seen a curious “ thorn”’-like structure 
exactly resembling small rose-thorns. A similar structure is 
seen on a dragonfly’s wing, only on that insect the “thorn” 
structure is scattered all over the wing, and not confined to 
a given area as in the Mayfly’s wing. This ‘‘ thorn” structure 
I have observed also on the outer abdominal appendages of a 
Mayfly larva (Cleon). The tail-filaments in the fly are also 
* “TJ found that when Hphemere fell upon a napkin spread over my 
knees they could only rise into the air with the help of their long tail-fila- 
ments.’’ And again: ‘‘ Now and then it rests upon the water with the help 
of the tail-filaments, so ... prevent the insect from sinking.’ —Swam- 
merdam. 
