A STUDY OF THE INHERITANCE OF DICHROMATISM 

 IN LINA LAPPONICA. 



ISABEL McCRACKEN. 



Stanford University, California. 



With i Plate and 3 Figures in the Text. 



I. INTRODUCTION. 



This paper contains a statement of breeding experiments with 

 a certain species of leaf-beetle, Lina lapponica, which have been 

 carried on this year (1904) in the Entomological Laboratory of 

 Stanford University. 



Lina lapponica is a small beetle of the family Chrysomelidae. 

 Both larvae and adults feed from early spring until late in the fall 

 on willow or poplar leaves. The females are, for the most part, 

 considerably larger than the males, although intergrading sizes 

 occur. 



The thoracic length of the smallest males is about 1.5 mm., 

 abdominal length 6 mm., thoracic width 2.5 mm., abdominal width 

 about 4 mm. Thoracic length of the largest females is about 2 

 mm., thoracic width 3 mm., abdominal length 7 mm., abdominal 

 width 5 mm. The wing covers in both males and females may be 

 entirely black, (PI. i. Fig. 6), or brown with fourteen black spots 

 (PI. I, Fig. 4). The eggs are elongate, yellowish, and laid side 

 by side upon the leaves of the plant furnishing food for both larvae 

 and adults. The life of each individual, in the early generations 

 of the season, occupies from three to six days in the egg stage, 

 from fifteen to twenty days (with two moults) in the larval stage, 

 and from four to eight days in the pupal stage. The adult stage 

 varies from twenty to thirty days. The adult stage of later genera- 

 tions is of longer duration. Each female produces from four 

 to six broods a season, each brood containing from thirty to forty 

 individuals. The number of generations in a year under normal 



