NOTES ON THE EPHEMERIDZ. AD5T 
small or wanting. They have a rudimentary mouth, and the 
body ends in two to three long anal set or long hair-like fila- 
ments. They are remarkable for undergoing four instead of 
three changes from larva to perfect insect, and when fully formed 
the pupa comes out of the water and issues forth from this stage 
as a pseudv-imago, looking exactly like the perfect fly, but 
covered wi’: ,3sisete,membrane, which after a time is cast 
off, and th, .. 4s. “saj4.sppears. The vast swarms of Mayflies 
seen over the Anions lakes are utilised and compressed with 
‘gnats in the form of cakes by the Africans.* 
The popular belief is that Mayflies in their perfect state in- 
variably die after the sunset preceding their time of development 
from nymph to fly. Many of them, it is true, live for a few 
hours only, though a period of two days is on record.t I myself 
have proved that their vitality is not so feeble as is generally 
supposed.t One specimen (Ephemera danica) was on my setting- 
board for three days, and then still retained signs of life, for 
when touched it responded by gently waving the long sete to and 
fro, although it had previously lain in the killing-bottle for quite 
five minutes. The long tail-filaments, when examined under a 
microscope, bear a close analogy in structure with the antenne 
of many insects, and doubtless serve the function of such, the 
true antenne being extremely small. _In this supposition I 
have frequently held live Mayflies by their wings, and they in- 
variably moved their sete in exactly the same manner that 
many insects move their antenne. A similar contrivance is 
found in the male Crickets (Gryllotalpa), which possess anal 
appendages covered with stiff hairs (an analogy to these is found 
in the Mayfly larve). These act as delicate organs of percep- 
tion, and are employed by the Cricket when moving backwards 
in its subterranean progress. The anal sete of the Mayflies 
serve another function when spread out (in exactly the same 
manner that the feathers in a bird’s tail are spread out); they 
assist in flight. When soaring upwards the sete are not spread 
* Theobald. : 
+ Miall, ‘ Natural History of Aquatic Insects.’ 
{| De Geer kept Ephemera vespertina alive for eight days, and Mr. 
Stephens mentions having kept specimens of Cleon dipterwm alive above 
three weeks (cf. Westwood, Mod. Class. Ins. vol. ii. p. 27, note).—Ep. 
Zool 4th ser. vol. XITI.. December. 1908. 2N 
