THE INSECT-GALLS OF THE VICINITY OF NEW 

 YORK CITY. 



Everywhere throughout the woods, along the roadsides 

 and in the fields, one finds on leaf or twig, stem or root peculiar 

 swellings which evidently are not part of the normal growth of 

 the plant . These deformations when produced by insects are called 

 Galls. Generally one or more eggs are inserted in a bud, a 

 flower, a leaf, a root or some other part of the plant, and the 

 presence of this foreign body, together with the irritation caused 

 by the larva among the vegetable cells, produces an abnormal 

 growth of definite shape and uniform structure. The variety 

 of Galls in respect to structure and substance is great. Every 

 species of Gall-producing insect attacks its own particular plant 

 and a particular part of that plant. Galls are of various sizes 

 and colors and of almost every conceivable shape. Some 

 resemble a tomato or a potato. Some are like the apple, plum, 

 cherry and other small fruits. Some have the appearance of a 

 pine-cone or a seed. They are smooth, wrinkled, downy, 

 hairy or covered with spines and other protuberances. Some 

 are succulent, while others are so fragile that they can be readily 

 crushed, and still others are so corky, hard and woody that it 

 requires a sharp knife to cut them. In color they are of many 

 shades of green, yellow, red, brown and white. 



The number of Galls formed by distinct species of insects and 

 mites is so large that only a small proportion of the excrescences 

 or of the insects causing them has yet been described. The 

 present Guide Leaflet gives brief accounts, illustrated by figures 

 draw^n to a uniform scale, of some of the more conspicuous Galls 

 made by members of the following families of insects found in 

 the vicinity of New York City : 



(i.) Hymenoptera (Cyxipid.-e and Tenthredinid.^) — Gall-flies and Saw- 

 flies. 



(2.) Diptera (Cecidomyiid.^, Mycetophilid.e and Trypetid-e) — Flies. 



(3.) Hemiptera (Psyllid.-e and Aphidid.-e) — Plant-lice and Jiimping- 

 lice. 



(4.) Acarina (Acarid.-e) — Mites. 



