SPATHEGASTER APRILINUS, 127 
S. albipes is found in the latter part of April only 
in very mild seasons, and when the foliage is well 
advanced. The second week in May is the usual 
time of development. Galls, from which the occupant 
has emerged, may occasionally be found in situ as late 
as the middle of September (one found September 
10th, 1907). 
The peculiar contraction, incision, or indentation, in 
one half of the blade of the leaf, often draws attention 
to the gall, when, otherwise it would be overlooked. 
Its pale colour also harmonises with the under-surface 
of the leaf rendering the gall less conspicuous. 
It is moderately common, and widely distributed, 
but somewhat local. Seldom more than one gall 
appears on a leaf, and more rarely is it seen growing 
from the petiole; but instances are known where 
galls are situated on either side of the mid-rib, and 
also of two galls side by side on the same margin. 
The side of the gall opposite that next the leaf is 
generally raised to form a slight ridge, or there may 
be a few minute protuberances. During growth the 
distal end of the gall terminates with a minute dark- 
coloured style which disappears at maturity, as also 
does much of the pilosity. 
It is somewhat remarkable that so small a gall, and 
the diminutive area it occupies, should arrest so large 
an amount of leaf tissue as is often the case, causing 
in some leaves an indentation more than fifty times 
the area of the gall. It is due to the fact that gall 
formation begins “on the rudimentary leaf while yet 
in the bud” (‘Alternating Generations’ p. 19), and 
when the leaf expands it cannot recover itself. 
Spathegaster Aprilinus, Giraud. 
(Plate LIT, div. A.) 
Neuroterus Schlechtendali, Mayr, Schltdl., F. Loew ; N. Aprilinus, i 
Cameron ; Spathegaster Aprilinus, Mayr, Licht., Beyer., Adler, Fitch. 
English name of gall.—*“'The April Bud Gall.” 
