THE LIFE-HISTORY OF THE BLACK-CURRANT GALL-MITE. 375 
very frequently observed, and on one occasion, in October, a 
species of Tarsonemus was found. These are vegetable feeders, 
and could not have been preying upon the Hriophyes. 
In a large proportion of the mite-infested buds dissection 
revealed the presence of a small dipterous larva, apparently that 
of a Cecidomyid fly (PI. 34. figs. 21,22). It was hoped that some 
examples would be reared and the imago obtained and identified, 
but its development is so slow that larve observed in October are 
little larger than those seen in July, and show no signs of pupa- 
tion. Probably the fly will not emerge until next spring, when 
it is quite likely to prove a new species. It is always found at, 
or near, the centre of the bud, and feeds upon the mites. Its 
slow growth probably implies a moderation of appetite which 
allows the mites, by their extreme fertility, to renew their 
numbers as fast as they are depleted, and thus to keep up the 
food-supply. 
The Red-Currant Plant and the Mite. 
As none of the characteristic swollen buds appeared on red- 
currant bushes, which, moreover, flourished in the immediate 
neighbourhood of failing black-currant plants, it was believed that 
the red-currant was practically immune. When the Cecidomyid 
larva above mentioned was first observed and some doubt was 
entertained as to its habits, red-currant buds were examined to 
see if they contained the grub, the inference being that the pre- 
sence of the grub would show that it fed upon the bud and not 
on the mite. 
The result of the examination was entirely unexpected, for the 
mites were found in considerable numbers. The attack differed 
remarkably from that on the black-currant, the infestation work- 
ing from the outside inwards. At first they were only found in 
the axils of the leaves at the base of the buds, and perhaps within 
the first brown sheathing-leaves. Later they penetrated more 
deeply and had almost reached the centre. 
That they were not merely sheltering there but were obtaining 
nourishment was proved by the presence of eggsandlarve. No 
ereat harm, however, seemed to be done by them, nor were they 
ever found except on bushes near to badly attacked black-currant 
plants. 
