1908 ENTOMOLOGICAL SOCIETY. 87 



Somewhat circular, about 4 mm. in diameter, projecting on both sides 

 of the leaf. Above dark red, below yellowish, about three times the thick- 

 ness of the leaf. Oak — Andicus papillatus O.S. — Plate C. fig. 5. Quercus 

 rubra. 



Irregular woody swellings of the midrib about 7-8 inch in length, sur- 

 face is glabrous or slightly pubescent and projects on both sides of the leaf. 

 Oak Midrib Gall — Andricus pige — Plate E. fig. 3. 



Globular, hollow gall, nearly always at the outer edge of the leaf blade. 

 From .9-1 cm. in diameter and comparatively thin walled. Oak Apple Gall 

 — Andricus singularis (Bass.) Quercus rubra. 



Cluster of dense, narrow leaflets, springing from a bud. Oak Leafy- 

 wreath GnW— Andricus topiarius (Ashm). — Plate C. fig. 6. Quercus macro- 

 carpa. 



B. — Galls on stem. 



Spherical gall, hard and woody with a small cavity in the centre. A 

 short joint at the apex distinguishes this species from Globulus. Pointed 

 Bullet Gall — Holcaspis duricaria (Bass.) Quercus macrocarpa. 



Har^, conical galls occurring in numbers on the stems. Oak Cone Gall — 

 Andricus ventricosus (Bass.) — Plate R. fig. 3. Quercus sp. 



Small, soft, bladder-like, one-celled structures, each about 1-3 of an 

 inch in diameter. Arranged in a cylindrical cluster along the stem of the 

 branches. Oak Fig Gall — Biorhiza forticornis (Walsh) — Plate C. fig. 2. 

 Quercus alba. 



Eosette or head of hard, brown, nut-like, wedge-shaped structures 

 fitting closely to one another and attached at the base to a small, spherical 

 receptacle about ^-1-3 of an inch in diameter. Pine-cone Oak Gall — Cynips 

 strohilana (O.S.) — Plate C. fig. 4. Quercus macrocarpa. 



Irregularly oval, woody gall encircling the stem. Polythalamous, con- 

 taining many cream-colored cases attached to the twig, each case looking 

 very much like an oat seed. Oak Seed Gall — Andricus seminator (Harr.) — 

 Quercus alba. 



Rough, hard, woody, somewhat globular, knot-like gall, encircling the 

 stem and varying greatly in size, but commonly 1-2 inches in diameter. 

 Oak Knot Gall — Andricus Punctatus (Bass.) — Plate C. fig. 1. Quercus 

 coccinea. 



Bullet-like, corky gall with a small cavity in the centre. On stem of 

 Burr Oak and White Oak. Oak Bullet GidH— Holcaspis globulus (Fitch). 

 Quercus macrocarpa and Q. alba. 



Club-shaped, hard and woody with often a few leaves growing from it. 

 A to 1 inch in length. Club Gall — Andricus clavula (Bass.)— Plate C. fig. 3. 



Affecting Poplar. 



A. Galls on the leaves. 



Small, circular, pimple-like elevations on the upper surface of the leaf, 

 with a corresponding depression on the lower surface. Pimple Gall. (Plate 

 P. fig. 3.) — Populus balsamifera. 



Leaf folded at its edge to form a red or green pouch over the gall which 

 is narrow and tent-shaped, and is formed from the leaf surface. Aspen 

 Tent Gall— Plate P. fig. 2. Populus tremuloides. 



Oblong enlargements of the petiole close to the base of the leaf. Nep- 

 ticula sp. — Populus tremuloides. 



Pear-shaped, mjonothalamous galls growing on the upper side of the 

 leaf and joined to the leaf by a slight constriction. Aspen Ball Gall — Plate 

 P. fig. 5.— Populus tremuloides. 



