EXISTING ORGANISMS— CLASSIFICATION 



21 



be called species, but that many of our named species blend into 

 each other so gradually that it is difficult or impossible to place 

 certain individuals accurately. These may not be species, and 

 ofti'n an abundance of material shows that such is the case. A 



Worker 



Queen 

 Fig. 5. — Honey-bees. 



Drone 



(From Hegner.) 



scientist may work with specimens from widely separated regions 

 and find them different, while the later acquisition of specimens 

 from intermediate regions shows that there is a gradual transition 

 from one to the other, or he may be confronted with great varia- 

 tion in a single local- 

 i t y, with blood 

 brothers bearing little 

 resemblance to each 

 other. The only possi- 

 ble conclusion of prac- 

 tical value is that 

 species are not all in 

 the same state; that 

 while many show 

 marked uniformity of 

 characters, others are 

 apparently unstable 

 and in all probability even now undergoing change. 



Subspecific Forms. The lack of fixed characters as a universal 

 basis for species is further complicated by the occurrences in many 

 of them of very different types of individuals which nevertheless 

 bear a definite and intimate relationship to each other. This rela- 



FiG. 6. — The Codling Moth Carpnrap.sa pnm- 

 onella. a, adult; b, larva in an apple; r, pupa 

 or chrysalis. (From Farmer's Bulletin 2S3, 

 U. S. Dept. Agriculture.) 



