SEASONS OF INSECTS. 5LL 
third might be indicated by the swarming of Melolontha 
vulgaris ; a fourth, by that of M. solstitialis; and the 
last, by the appearance in numbers of Aphodius ciliaris, 
which in the autumn fills every horse-dropping. 
Some insects are so ephemeral, that they are to be 
found in numbers only for a few days, and then disap- 
pear for that season. Of this description are the Ephe- 
mere, much of whose history has been detailed to you. 
Those of which De Geer has given an account (EZ. vul- - 
gata) appeared about the end of May or the beginning of 
June, and continued about a fortnight? ; while those 
which Swammerdam observed did not come forth till 
the middle of June, and lasted only three days. The 
same period distinguished those of which Reaumur has 
compiled so interesting a history, but they did not show 
themselves before the middle of August®. My kind 
friend Mr. Marsham not long before his death copied for 
me some memoranda he had made with respect to the 
sudden appearance of Cercopis bifasciata F. On one 
occasion the white dress of a lady sitting upon a hay- 
cock was covered by these insects; but on the following 
day the same steps were taken at the same time to pro- 
cure some, when after the most diligent search not a 
single one could be found. The same circumstance was 
observed a few years afterwards by another friend of 
his. He himself was of opinion that the insects in ques- 
tion were then migrating‘. 
I may here observe, that the London amateurs have 
particular seasons for collecting moths. For the zmago 
they go into the woods in April, May, June, and Octo- 
* De Geer ii. G38—. 641—. 
> Swamm, Bibl. Nat. i. Conf. 114 with 103. 
* Reaum. vi. 480—. EO Voretlepa il: 
