New York State Museum Bulletin 



Entered as se^oni-class matter November 27, 191S, at the Post Offi:e at Albany, New York, 

 under the act of August 24, 1912 



Published monthly by The University of the State of New York 

 No. 200 ALBANY, N. Y. August i, 1917 



The University of the State of New York 



New York State Museum 



John M. Clarke, Director 



KEY TO AMERICAN INSECT GALLS 



BY 



ephraim porter felt d. sc. 



INTRODUCTION 



Insect galls are obvious and frequently excite surprise because of 

 the strange fomi or the wonderful coloring and delicacy of structure. 

 The fresh, well-developed gall of the wool sower is one of the most 

 beautiful of natural objects, while the delicately colored galls of 

 Itonida anthicion bald cypress may occasionally be found in 

 such numbers as to suggest a beautiful group of dainty flowers, struc- 

 tures very different from what normally occur on this tree and there- 

 fore even more surprising. The great variety of galls found upon 

 the oaks and the interesting alternation of generations characteristic 

 of the gall wasps challenge our admiration and incite to further 

 study. The same is true though possibly to a less marked degree, 

 of the hosts of fragile gall midges, forms which have learned to 

 subsist upon various portions of a very large number of plants and, 

 like the gall wasps, offer many biological puzzles to stimulate the 

 earnest inquirer. Much of this is also true of the gall-making 

 plant lice with their migrations and very dissimilar alternate host 

 plants. 



The origin and development of these growths are no less interest- 

 ing than the deformities themselves. The gall-making habit among 

 insects has undoubtedly developed independently in several widely 



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