362 PROCEEDINGS OF THE AMERICAN ACADEMY. 



variation, and why should not the characters peculiar to a distinct 

 variety, or even species, arise during the lifetime of two individuals 

 when mated ? Many individuals die without being mated ; an unusu- 

 ally vigorous polygamous butterfly may have some new congenital 

 extra development of hooks and processes, and by frequent use develop 

 the muscles controlling these to the extent of providing an acquired 

 character, which may be, if useful, inherited in the next and succeed- 

 ing generations. 



But an especially interesting and fruitful field of investigation 

 would be a study of wingless Lepidoptera, such as the canker-worm, 

 the autumn moths allied to it, the tussock moths (Orgyia), and especially 

 the sac-bearers or Psychidae. 



The loss of wings in these cases seems originally to have been due 

 to disuse in certain individuals more sluggish than others, and with 

 little doubt has been the result of inheritance of what were originally 

 acquired characters. It is easy to imagine how this has been induced 

 by a study of a series of forms beginning with certain European 

 genera in which the wings of the female are very small, and passing 

 to those in which they become simple pads, as in the Orgyia, and 

 ending with those, such as Anisopteryx, in which their reduction is still 

 further carried out. And then examples like those should be com- 

 pared with certain of the Ephemera?, whose hind wings are so much 

 reduced ; with Pezzotettix and other Orthoptera with aborted wings, 

 and certain Hemiptera in which the wings are aborted, ending with 

 the great order of Diptera, comprising a vast number of species in 

 which the hind wings have not only undergone a great reduction, but 

 have been transformed through change of function into balancers, 

 with their extraordinary sense-organs. It is not difficult to see that 

 the disuse of wings may have begun in the life of a single individual, 

 which, losing its wings, having perhaps inherited a tendency to thi3 

 lesion through corpulency and other bodily changes, became inactive, 

 averse to flight, and finally transmitted the peculiarity or the tendency 

 to such peculiarity to its offspring.* 



In a paper in the Proceedings of the Boston Society of Natural 

 History (XXIV. 482) on the life history of Drepana arcuata, I have 

 described the different stages of this moth, and at the end recapitu- 

 lated the congenital characters, and finally given a synopsis of the chief 



* L. Knatz (Archiv fur Naturgeschichte, LVII. 49-74, 1 pi., 18G1) mentions 

 183 instances of reduced wings, and states that the reduction in wings is ac- 

 companied by an enlarged abdomen and an increase in the size of the ovaries, 

 with greater fertility. Journ. Royal Microscopical Society for 1801, p. 4G2. 



