STUDIES OF VARIATION IN INSECTS 



22 3 



sibility and even probability (a condition actually confirmed by 

 the statistical study) of a variation in these dimensions due to 

 the varying situation in the wing area of the cross veins or the 

 varying earlier or later (in point of distance from the base of the 

 wing) forking or branching of the veins, which should be wholly 

 or nearly independent of the size of the wing. 



In figure n are indicated the parts of veins measured, and 

 the symbols by which these parts will be referred to in the tabu- 

 lation of results. All measurements were made under magnifi- 

 cation by one person using the same microscope, lenses and 

 ocular micrometer throughout the work. 



The breadth and the parts of veins indicated in figure n as b-d, 

 f-g<> and g-h) were measured in the right fore wings of 300 

 drones from the laboratory hive (Italians), (the same lot whose 

 wings were mounted and studied for variation in character of 

 venation with the results given on p. 214). 



The frequency polygon showing graphically the variations in 

 breadth (indicative of size of the whole wing) and the size or 

 frequency of the various classes in this series of 294 individuals 

 (six individuals had broken right fore wings) is as follows : 











FIG. 12. Frequency polygon of the variation in width of the right fore wings 

 of 294 drone honey bees taken from laboratory hive at one time ; mean width 

 67.9 micrometer units; index of variability 1.8; coefficient of variation 2.65. 



