SPATHEGASTER APRILINUS. 127 



S. aJhipes 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 occasionall}^ 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 LII, div. A.) 



Neuroteriis Scldeclitendali, Mayr, Scliltcll., F. Loew ; N. Aprilinus, 

 Camei'ou ; Spathegaster Aprilinus, Mayr, Licht., Beyer., Adler, Fitch. 

 English name of gall.—" The April Bud Grail." 



