7 6 



VARIATION IN LEPTINOTARSA. 



Table 22. Variation in color of epicranium in L. haldcmani. L. libalri.v. and 



I,, violescens. 



L. haldemam : N. = 200 individuals. Mean of classes = 1.62. 

 L. libatrix : N.= 300 individuals. Mean of classes = 4. 10 

 L. violescens : N. = 100 individuals. Mean of classes = 6 84. 



Individual Variation in the Color Pattern of the Elytra. 



The elytra present more interesting and significant variations in their color 

 pattern than do any other portion of the body, and the fact that their color 

 characters are used as specific differentials adds much interest to a study of 

 their variation. 



An elytron has six veins (text-fig. 1), between which there are six inter- 

 spaces where pigment is laid down. This deposition of pigment gives either 

 stripes or rows of spots as found in the lineata and dilecta groups (plate 14, 

 figs. 31 to 48), or in other members of the genus transverse bands, or rows of 

 spots in transverse series, situated at definite points upon the wings (figs. 

 49 to 57). In the whole genus the transverse markings occur at definite 

 and homologous points upon the elytra, and in their modifications follow 

 certain well-defined laws. 



Variation in ike elytral markings in the lineata group. The elytra of this 

 group all present a color pattern composed of alternating stripes due to the 

 deposition of cuticular and hypodermal pigments. These dark and light 

 stripes are situated, the one between the veins, and the other over the veins 

 (text-fig. 1 ), excepting that between the subcostal and ramous veins there 

 are two stripes of dark color which behave very differently from the others, 

 and rarely there are found elements of transverse bauds producing transverse 

 fusions. The extreme reduction of the anal portion in the elytra in Coleoptera 

 has compressed the anal and cubital areas into a narrow zone along the inner 

 border of the elytra. 



In the twelve species of this group the variation consists of an increase or 

 a decrease in the dark color. The extremes of variation in color are repre- 

 sented by L. signaticollis (plate 14, fig. 33) and L. melanothorax or L. unde- 

 cimlineata (plate 14, figs. 31 and 34), while the extremes of lateral fusion 

 between the longitudinal stripes are represented by deecmlineata and undecim- 

 lineata (plate 14, figs. 34, 36, and 37). The variations of increase and decrease 



