816 THE ENTOMOLOGIST. 
a small spider the exact colour of uncooked meat, which, in 
the same way, had entrapped two hive bees by lurking 
within the blossoms of Cnicus pratensis, from which it was 
undistinguishable in colour, and thus the unwary bees had 
visited their accustomed haunts, little thinking of the deadly 
enemy which awaited them therein. J presume that all these 
three instances are cases of “mimicry.” I shall gladly send 
you the flowers, the spiders and the bees, if you think it 
worth the trouble of seeing them.—C. W. Penny; Welling- 
ton College, Wokingham, May 15, 1871. 
I am greatly obliged by the offer of the insects and 
flowers, but I have seen so many similar instances that I 
require no ocular proof of the facts related. There can 
scarcely be a doubt that the colour of the spider is for the 
purpose of concealment, but it is not, as is so commonly the 
case, protective. The tendency of concealment in these 
cases is rather destructive than protective, at least in the case 
of the bee. 
Works on Coleoptera and Diptera—Is it your intention 
to bring out a book on either of these classes? as I am sure 
it would meet with as enthusiastic a reception as your 
Lepidoptera has already received.—S. 7. Klein ; Haileybury 
College, Herts, May 1, 1871. 
I have no such intention; and I rather doubt the enthu- 
siastic reception. Diptera are especially unpopular. 
Error in British Moths.—Wave not you got Plusia 
chrysilis figured as Festuce, and vice versd ?—C. E. Hol- 
ford; High Oak House, near Ware. 
I think you will find this—which is a printer’s, not - 
an author’s, mistake—corrected in p. 476 of the same 
work. 
Gall on Salix nigricans.—A beautiful gall, of a bright 
scarlet colour and spherical form, occasionally makes its 
appearance on the upper side of the leaves of the black 
willow, always singly, and of that uncertain size generally 
compared to a pin’s head. A specimen has been examined 
by one of our best-instructed students of this family of 
vegetable productions, Mr. H. W. Kidd, of Godalming, and 
it proves to be quite unknown to him. Can any other 
correspondent give it a name; the description, however im- 
perfect, will distinguish it from all the other galls occurring 
