248 



KELLOGG AND BELL 



cence, this varying degree being indicated as much coalescence, 

 median coalescence, very little coalescence. Correlating this 

 character in right and left wings it is found that in 144 indi- 

 viduals both wings exhibited the same degree of coalescence of 

 the veins, in 54 individuals one wing was median with the 

 other either much or very little, and in no individual did one 

 wing show much and the other very little. Of the 144 cases of 

 indentical coalescence in both wings 74 were median, 43 much 

 and 23 very little on both sides ; of the 54 cases of a combina- 

 tion of median with one of the extremes, the combination was 

 median + much in 30 individuals and median + very little in 

 24 individuals. The right and left correlation, /. c.^ bilateral 

 symmetry, of the variations in this character of a modification in 

 venation, is thus seen to be a nearly perfect one. 



The variations in the measurements of the fore wings are in- 

 dicated by the frequency polygons which follow. Four meas- 

 urements were made (with micrometer, the wing being mounted 

 flat and examined under the microscope) for each wing, viz., 

 length, width, the length of a part of the cubital vein sub- 

 tended by a cross vein and a point of forking (indicated as C 



50i 



^- 30 



]| i i ! i i ;4m{-|U[Uj:p4f-!: 



wmm 



Fig. 37. Frequencj polyi^oii of llic vaiialion in Icnglh of left foie wings of 

 191 male black ants collected atone time in one place; mean ^'9 micrometer 

 units; index of variability 3.28; coclVicient of variation 3.7. 



