88 VARIATION IN LEPTINOTARSA. 



and in dccemlincata show similar conditions. In species like signaticollis and 

 angustovittata the punctations become more variable. In all but two of the 

 species of the group the punctations are arranged in irregular double rows, as 

 in undccimlincata, dccemlincata, and signaticollis. These irregular double 

 rows allow of considerable latitude in variation. In signaticollis the lateral 

 displacement is often so extreme that the rows of punctations are almost 

 indistinguishable. In two of the species, however, juncta and defccta, the 

 punctations occur in a single even row, without any observable lateral devia- 

 tion. In these two species, juncta and defccta, the variation occurs almost 

 entirely at the distal and posterior portions of the wing. In reduction the 

 distal and anal punctations disappear first, later the proximal and costal, and 

 last of all the subcostal. 



The arrangement of the punctations and some of the variations in L- cal- 

 ceata, dilecta, and lincolata, in the dilccta group show, as in dilccta, a decided 

 tendency to reduction at the interbands, and this system of ornamentation, 

 like that of the coloration, is much reduced distally and in the anal area of the 

 elytron. The purely fluctuating variations in the dilccta group are not as 

 numerous nor as extensive as in the lincata group. In the dilccta group, 

 however, the variations tend to reduction of the stripes and bands and to pro- 

 duction of spots or rings of punctations which surround the color areas. In 

 species like L. zettcrstcdti this reduction of the stripes and development of the 

 bands is more pronounced, although the stripes are still recognizable. In 

 lacerata, pudica, and modesta are found variations in which the system of 

 bands is prominent, and the stripes are largely obscured. In the unicolorous 

 species, such as haldcmani and violcsccns, the system of stripes is variable to 

 a considerable extent. 



It is found that the punctations vary in some directions and not in others. 

 Moreover, the stripes and bands vary most in the apical and anal portions of 

 the wing, to some extent at the proximal end, and least at the center. Finally, 

 they follow the same line and the same direction of variation as do the color 

 areas of the elytral color pattern. There is apparently a strong correlation 

 between the two. 



In the quantitative study of the punctations the plan has been to seriate 

 them into classes by inspection, and to some extent by counting. The fre- 

 quent variations of this character, found on seriating, while not showing 

 much that is of interest, confirms the conclusions reached concerning indi- 

 vidual variation in the color character of the elytra by evidence derived from 

 structural characters. The seriated variations shown in table 30 are com- 

 pletely in accordance with those of the color characters, and, like them, 

 follow Quetelet's law. The smaller punctations, in their variations, also 

 follow the same laws as do the larger ones. 



