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BULLETIN OF THE 



primaries are similar variations in the relative length of the inner secon- 

 daries as compared with the outer secondaries. Relatively short inner 

 secondaries (generally improperly called " tertiaries ") hence ac- 

 company long primaries, and, conversely, long inner secondaries, 

 short outer primaries. The particular form of the wing in any group 

 depending upon the relative development of these several elements, 

 they hence afford excellent generic characters ; but while thus impor- 

 tant, they are subject to a considerable range of individual variation. 

 The form of the wing being readily determined by measurements, 

 and easily expressed mathematically, the amount of the variation i3 

 easily measured and tabulated. In the following table (Table E) the 

 extent and character of this variation is to some degree illustrated. In 

 the first column of measurements is given the length of the folded wing; 

 in the second the extent of the longest primary beyond the outer (or 

 shortest) secondary, and in the third the extent of the longest pri- 

 mary beyond the inner (or longest) secondary. The fourth column 

 gives the amount of variation in each specimen cited. 



Table E. — Variation in the Form of the Wing. 



