180 THE ENTOMOLOGIST. * 
dames of the flies that the ravages of all their Fens eee ange 
no appreciable diminution in their numbers. Mile after mile, 
from bank to bank, the river seemed covered with them, when — 
all at once, as if by signal, the whole of them rose up confusedly, 
flying aloft in a thousand different directions, producing an effect 
in the air like that of a heavy fall of snow; then they descended 
again and the snow seemed to cover the river with a white layer. 
The males very largely outnumbered the females.’’. Haton also 
mentions (op. cit., p. 24) that according to Mr. Snellen, of 
Rotterdam, Swammerdam’s statement that P. longicauda appears 
in vast multitudes during one or two evenings only every year 
“on or about the Feast of St. John” is generally correct, but: 
the date of the swarm is liable to be earlier in warm seasons, 
sometimes as early as June 10th. Reference may also be made 
to the great swarms of Oligoneuria rhenana which appear on the 
Rhine, and whose duration is limited to a day or two (Muller, 
‘Hh. M. M.,’ vol. i, p. 262, and vol. 11, p. 182). Polymitarcys 
virgo, Oliv., another mayfly, also appears in great numbers on 
some of the larger European rivers, giving rise to the local 
name ‘‘la manne,” and the accumulations of the dead bodies of 
this species have in some parts of Germany received the name 
of ‘* Uferaas.” 
Mr. Martin E. Mosely, ever ready to assist, kindly made for 
me a fine series of slides of the wings and other details, and 
provided the photograph of the whole insect. For the photo- 
sraph of the wings I am indebted to Mr. R. M. Adam, of the 
Royal Botanic Gardens here. 
EXPLANATION OF PuateE II. 
1. Wings of g (x about 4). 
2. Whole insect, ¢ (x about 14), sete incomplete. 
3. Forceps of ¢ from beneath; (a) apex of penis lobe from above. 
4. Head of ¢ from above; two basal joints of antenne only shown; position ~ 
of anterior ocellus uncertain. 
Fig. 1, from wings mounted in balsam; the others from examples in fluid. 
13, Blackford Road, 
Edinburgh ; 
June 11th, 1920. 
SOME UNDESCRIBED RHOPALOCERA IN THE BRITISH ~ 
MUSEUM (NAT. HIST.). } 
By: N. D,. :Riney, -F.8.5° F248. 
PaPILIONIDE. 
Papilio aristeus leneus f. interrupta f. nov. 
The form of P. a. leneus in which the yellow discal 
band of the hind wing uprer-side is incomplete is sufficiently 
common, and also it seems, in the Chaquimayo district at least, 
in §.E. Peru, sufficiently constant to requirea name. In this 
form typically all trace of the band in question is entirely absent — 
