256 The Ohio Journal of Science [Vol. XVI, No. 7, 



KEY TO GALLS OF CELTIS OCCIDENTALIS. 



1. Twig galls; twigs massed and showing enlargement of bases, witches broom. 



Eriophyes sp. (1). 

 L Twig galls; aborted lateral twigs, isolated not aggregated, Lepidopterous 



gall, (2). 

 1. Twig galls; simple low, ovoid swellings on sides of twigs, Pachypsylla sp., (4). 

 1. Bud gall; an abnormal enlargement of bud, Pachypsylla gemma, (5). 



1. Galls on leaves and twigs, if on latter very different from foregoing. 2. 



2. Gall of petiole, pear-shaped, large, involving entire petiole, Pachypsylla 



venusta, (7). 

 2. Leaf gall, blister-like, projecting but slightly from either side of leaf, 

 Pachypsylla vesiculuin, (3). 



2. Leaf and twig galls, projecting prominently; definite appendicular structures. 3. 



3. Leaf blade only; definite concavity on side of blade opposite gall, Pachypsylla 



mamma, (6). 



3. Leaf blade, petiole and twig galls, on blade never showing concavity on side 



opposite the gall; itonid galls. 4. 



4. Galls definitely conic; body of gall contracted distally. 5. 



4. Galls definitely obconic; body of gall contracted proximally. 8. 



4. Galls definitely globular, Cecidomyia sp., (14.) 



4. Galls otherwise. 9. 



5. Galls with ends attenuate, 6. 



5. Galls with ends truncate (small nipple in center) 7. 



6. Galls small, 2-3 mm. long, base not prominently expanded, Cecidomyia sp., (11). 



6. Galls larger, 3-5 mm. long, base prominently expanded, Cecidomyia tingui- 



cola, (8). 



7. Galls coarsely pubescent; distal half rather sharply constricted from basal, 



Cecidomyia sp., (13). 

 7. Galls smooth; distal half not constricted from basal half; stoutly conic, 

 Cecidomyia sp., (12). 



7. Galls smooth, larval chamber falls from the socket-like base. Cecidomyia sp. 



(16). 



8. Gall sub-balloon-shape; basal half definitely constricted from distal expanded 



half, coarsely pubescent, Phytophaga celtiphyllia, (9). 



8. Gall top-shaped; basal half not definitely constricted from distal half, finely 



pubescent, Phytophaga well si, (10). 



9. Gall greatly flattened with central nipple; more or less prominent vertical, 



peripheral ridges present. (See end of introduction to the descriptions of the 

 Itonididse galls). 



9. Galls relatively large, with very prominent, vertical, wing-like ridges pro- 

 jecting from the body of the gall, Cecidomyia sp., (15). 



9. Galls generally in masses, larval chamber eventually loosening and dropping 

 from the loasal parts, Cecidomyia sp., (16). 



Fam. Eriophyid^. (Ord. Acarinae). 



This family includes the vast majority of the gall-forming 

 mites. The galls are of simple types, though exhibiting great 

 diversity. Most of the mite cecidozoons affecting the American 

 flora, are undescribed, a condition related to the fact of their 

 minute size and soft body, characters which demand a special 

 technique to handle them. The majority of gall makers are 

 members of the genus Eriophyes. 



1. Eriophyes sp. This gall, a typical witches-broom, 

 (PI. XIX, Fig. 1) represents a more or less serious disturbance 



