THE LIFE-HISTORY OF THE BLACK-CURRANT GALL-MITE, 367 
The Eriophyide. 
The Eriophyidze (Phytoptide) or gall-mites are vermiform 
Acari, possessing only two pairs of legs, which have no claws, 
but are furnished with bristles and “ feather-hairs” (Pl. 33. 
fic. 8; Pl. 34. figs. 10,11). The elongated body is transversely 
striated, and terminates in a muscular disc-like organ (Pl. 33. 
fig. 9; Pl. 34. figs. 12, 13). It also presents certain bristles, of 
which the most important are a pair proceeding dorso-laterally 
from above the tail-disc. 
About two hundred species of gall-mites have been described. 
They are all of small size, and are vegetable feeders, usually 
causing the abnormal growths known as galls on the leaves or 
stems of the plants they infest. 
The Black-Currant Disease. 
The disease is easily recognized by the presence, on infested 
bushes, of swollen and distorted buds, which, if still green, are 
found on examination to contain large numbers of the parasite. 
Badly attacked buds are entirely abortive, and eventually remain 
on the stems as brown dry knobs from which no leaves have 
arisen (PJ. 33. fig. 1). In milder cases of attack sufficient 
vigour is retained to give forth an enfeebled shoot (Pl. 33. fig. 2). 
As the hold of the disease upon the plant increases the effect 
becomes very striking. The failure of a large number of the 
buds forces into premature development the buds which would 
normally burst forth the following year, making overdrafts, so 
to speak, on the plant’s vitality, and a stage is reached when it 
is no longer able to respond to the excessive calls made upon it. 
The provision for next year’s foliage is already exhausted and 
the plant dies. 
Life-history of the Mite. 
The observations here recorded began on May 20, 1901, and 
were carried on without intermission until the middle of October. 
On May 20, of last year’s wite-infested buds, ‘those of which 
the growth had been entirely arrested were in some cases 
cracked, mites being visible externally in the fissures. 
Individuals were also found wandering on the stems, Clearly 
the migration from the abortive buds had only recently com- 
menced. Mites have been recorded by Newstead and othersjas 
wandering on the plants much earlier in the spring. It is 
Die 
