ANDRICUS CTIRVATOIJ. 57 



stubs as on young and old trees. The leaf is consider- 

 ably distorted by the growth of the gall, and fre- 

 quently the material which would have formed a leaf 

 is almost absorbed in the formation of the gall, a small 

 portion only developing to form a ridge or frill upon 

 the surface. Under such conditions of growth the 

 gall-mass is usually more or less globular, but when 

 situated upon the blade of the leaf the shape is 

 very irregular, although the bulk may not be more 

 than normal. 



A solitary mature globular specimen on the end of 

 a twig, having little or no leaf membrane attached, 

 has the appearance of a small gall of Gijnips Kollari. 



Growth is rapid, and during the early part of the 

 time the gall is solid and firm, although somewhat 

 succulent, and it extends in equal, or nearly equal, 

 proportions on both surfaces of the leaf. As maturity 

 approaches a large cavity is formed, within which is 

 the inner gall ; a small, reddish-brown larval cell, ovoid 

 in shape, loosely adherent, with very thin walls, and 

 about 2 mm. in its long axis, occasionally with a minute 

 papilla at one end. 



Tw^o, three, and sometimes four galls will anastomose, 

 and upon cutting the mass open it will be seen that 

 the inner galls are in some cases separated l)y very 

 thin septa, or the cavity remains undivided. 



When gall growth takes j)lace at the base of a 

 petiole the whole of the petiole is involved and a con- 

 siderable swelling results. When situated at the 

 extremity of a twig, and small portions of leaves 

 develop upon the gall structure, there is a close 

 resemblance to a gall of A. iiiflator. 



It is extremely abundant on some trees, affecting 

 mostly the small twigs springing from the trunk, where 

 not infrequently almost every leaf is galled. It may 

 also be found in great plenty on bushes and very young- 

 trees. Apparently it occurs but rarely on the higher 

 boughs of old trees. 



Some of the imagines of Ai^hilothrix collaris emerge 



