136 Isabel McCracken. 



In conclusion it appears from this single year's observations 

 that dichromatism and variability are two distinct characteristics 

 as represented in this species. The heredity of the dichromatism 

 is such that if any barrier should interpose to intercrossing between 

 the two types, each would eventually become permanently estab- 

 lished. In this seems to lie its only evolutionary significance. 



Explanation of Plate. 



Fig. I. Lina lapponica, immediately after casting pupal skin, showing absence of pigment in elytras. 



Fig. 2. Lina lapponica, 10 or 15 minutes after casting pupal skin, spotted areas outlined in elytras. 



Fig. 3. Lina lapponica, 15 or 20 minutes after casting pupal skin early drab stage of both S and B 

 types. 



Fig. 4. Lina lapponica, about 45 minutes after casting pupal skin, S type (mature). 



Fig. 5. Lina lapponica, 20 or 25 minutes after casting pupal skin, later drab stage of B type. 



Fig. 6. Lina lapponica, about 45 minutes after casting pupal skin, B type (mature). 



