456 
[March 
nated and gradually cease to make its appearance. As an apparent 
confirmation of the hypothesis that aciculata produces % % exclusively, 
Baron Osten Sacken has called my attention to the fact, that “ he found 
three galls in the spring on the same branchy and on cutting them open 
found % spongifica in two and the third was probably also a S ( See 
Proc. Ent. Soc. Phila. I, p. 244.) May it not be possible that the 
working-bee generates % bees more frequently than has been supposed, 
so as to admit of a queen bee being occasionally fertilized by one of 
them ? On this hypothesis a difficulty which has much exercised Mr. 
Darwin would be thoroughly cleared up, viz., how instincts acquired 
by “ neuter insects come to be inherited. ( Origin of Species^ chap. 7.) 
The small 9 9 of Bomhus are normally fertile; analogy would lead us to 
suppose that the 9 of Apis should be at least occasionally fertile. May 
not the well known fact that in certain insects one or the other sex 
greatly preponderates in numbers, and the further fact, so familiar to 
all breeders of insects, that with a given species one brood will be almost 
exclusively S and another brood almost exclusively 9 , be also ac¬ 
counted for on the above theory ? 
In regard to the second problem, it may be asked why, if Hartig’s 
agamous species are mere dimorphous forms of bisexual species, did 
he fail to discover the bisexual forms ? I can only say in reply, that I 
once argued in print, that it was impossible that the army-worm moth 
{Leueania unipuncta Haw.) should exist in the Eastern States, for if 
it did it must have been found there either by Dr. Harris or Dr. Fitch; 
and that scarcely had the argument been published, when it was proved 
by indubitable evidence that it did so exist. Negative evidence is at 
the best always more or less unreliable. I recollect distinctly that the 
common English “ oak-apples” which are, I believe, formed by Cgnips 
quercus terminalis^ attain their full size like the North American oak- 
apples of spongifica^ by the end of May, because 30 years ago it was 
the custom to cover them with gold-leaf and employ them in the cele¬ 
bration of King Charles’s day, May 29th. Will not some English en¬ 
tomologist collect a hundred or so of them and see if they do not pro¬ 
duce a dimorphous 9 form in the autumn ? 
To those who are desirous either of verifying the dimorphism of 
spongifica and aciculata^ or of investigating the probable dimorphism 
of European species, it may be suggested that a very cheap, convenient 
