The Chromosomes in Diahrotica 



465 



mosome, and there were several individuals of intermediate size 

 which had one or more supernumeraries. In June, July and 

 August, 100 males of Diahrotica soror were studied in California. 

 The length of the elytron from origin to tip, measured to the 

 nearest fourth of a miUimeter in a straight line — not over the curve 

 — was recorded for each beetle, the insects numbered and kept 

 for future reference. After the hundred had been collected, 

 measured and studied, they were arranged in series according to 

 nuclear type. It was at once evident that the insects of type I and 

 type II were about equally variable in size, and that all of the varia- 

 tions in fusion of spots occurred in each type. In fact no constant 

 difference in external characters could be detected which might 

 indicate two species. Thinking that possibly the variability in 

 size might be different in the early and late broods, two lots of 

 100 each were collected November i and December i, 1907, and 

 measured without regard to the character of the germ cells. The 

 results are given in a table below. Meanwhile 100 males of 

 Diahrotica 12-punctata had been collected, measured, and the 

 testes studied in aceto-carmine in October, 1907. This species 

 is somewhat less variable than Diahrotica soror, but1:he two types 

 with reference to the supernumerary chromosomes show the 

 same kind of variations. 



The variability in length of elytra of the different species and 

 types is shown in Tables I and II. 



TABLE I 



Diahrotica soror. 



Length of elytron in mm 



Type I, o 5 



Ila, I i 



lib, 2i 



lie, 35 



IId,4i 



June 23 to August 7 . . . . 



November i 



December i 



Total 



3-25 



3-5 



3-75 



4 4-^5 



4-5 



4-75 



5-^5 



5-5 



5-75 



14 



loa 

 100 

 100 



43 I 35 



40 



66 



