8o 



VARIATION IN LEPTINOTARSA. 



In the preceding table are shown conditions similar to those found in the 

 epicranium and pronotum that is, variation in the position of the modes of 

 the different species upon the scale of values, and the wide difference in the 

 percentages of the scale covered by the range of each species. When pre- 

 sented in tabular form these conditions become more evident. 



Table 25. Position of the modal condition of the species of the lineata group in the 

 scale of values used for proportion of light to dark color in the elytra; also the per 

 cent of total range covered by each species and per cent of variation in modal class. 



Comparison of the above table with tables 14, 18, 19, and 20 reveals the 

 fact that there is in the variation of the elytra the same racial tendency to 

 proceed in a definite direction along a given line of modification, and that 

 each species of the group is segregated about a modal condition which is 

 placed in the main at similar positions along the scale of value used for the 

 different parts. Among the various species the only conspicuous difference 

 between the modal states of the elytra and those of the pronotum and 

 epicranium is found in L. signaticollis, which is at the lowest end of the scale 

 in the elytra and high upon the scale in the pronotum and epicranium. 



Variation in the elylra of the dilecta group. The elytral color pattern con- 

 sists of longitudinal stripes, as in the lineata group, and certain spots belong- 

 ing to the second, third, and fourth transverse bands. The longitudinal 

 stripes show, moreover, a striking tendency to reduction and to division 

 between the second and third transverse bands, and the entire absence of 

 the costal, anal, and cubital stripes. Only the two subcostals, the ramous 

 and the median stripes, are found, and these are often greatly reduced. On 

 plate 14, figs. 41 to 48, are shown some of the variations which the color 

 patterns of the elytra of this group undergo. The same two directions of 

 variation are found, the longitudinal and the transverse, but in this group 

 the variation in the transverse direction is much more pronounced, all modi- 



