236 THE ENTOMOLOGIST. 
about ten days, but I am glad to say that now only a few 
stragglers remain. I do not think I exaggerate when I say 
that there must have been thousands of them in my room 
where I was performing some operations with cantharides. 
If you can tell me anything of their history, and where they 
are likely to have come from, I shall be greatly obliged by 
your doing so. 
[The fly is unquestionably Musca pluvialis; but with 
regard to their economy I have to confess my entire igno- 
rance, and shall be obliged for information. I have not only 
heard of, but known, instances of flies assembling indoors in 
such large numbers, but I cannot find out the attraction, or 
what it is that induces a line of conduct apparently so much 
at variance with their general habits—Hdward Newman.| 
T. R. Archer Briggs.—Gall on Potentilla reptans.—I en- 
close specimens of another gall from the neighbourhood of 
Plymouth, and shall be very glad to know the name of it, 
although it may prove to be but a common one. I found it 
on the 30th of August, in a pasture in the Tavy Valley, near 
Plymouth, Devon, occurring, as you will see, on the stems 
and petioles of the creeping cinquefoil (Potentilla reptans). I 
do not remember to have noticed it previously. 
[Mr. Fitch kindly hands me a reply, as under :— I believe 
this gall is included, both by Marshall and Miiller, under 
Curtis’s name of Brevicornis, which is probably a synonym 
of Aulax Potentille of Hartig; or, as Foester has it, Xesto- 
phanes Potentillz de Villers = Aulax splendens of Hartig.” 
—E. A. Fitch.] 
Joseph Anderson, jun.—Lffect of Acids on Green Insects. 
—I have in my cabinet a foreign beetle resembling a 
gigantic specimen of Aromia Moschata. The name of it is, I 
believe, Golofa Porteri, and it should be a brilliant green 
colour; but one day, thinking to “ kyanise” it, I saturated it 
with phenic acid, and was mortified by seeing it change to a 
coppery red. Could you, or any of your correspondents, tell 
me of an alkali that would be likely to restore the original 
colour? 
(‘The effect of acid on the colours of insects is so great that 
it is better to avoid the use of them altogether. In the case 
of metallic colours it is less observable than in the delicate 
wings of Lepidoptera. 1 cannot mention any drug from 
