196 STUDIES IN THE GENUS THANAOS 



other only by a twist or two in the shape, or the millionth of an 

 inch difference in the size of the organs of generation." 



This was the general attitude of the students of butterflies at 

 that period and even at present there are some persons who refuse 

 to consider the genitalia of any importance in specific separation. 

 One of my objects in studying the genus from a genital ic stand- 

 point was to discover the amount of individual variation in a given 

 species and then estimate their value for specific differentiation. 



I was not sure that Scudder and Burgess had dissected enough 

 specimens to determine the amount of individual variation in the 

 species. That they did not, may be inferred from the fact that 

 Dr. Scudder mistrusted some of their conclusions in their paper, 

 as he subsequently put some of the species into the synonymy. 



A number of years ago I wrote to him asking for the technic or 

 method of extracting and mounting the genitalia for study. He 

 replied that he could not tell me as all that part of the work had 

 been done by Burgess who was dead. It will be noted that these 

 slides or whatever form they are in, are the types of Scudder and 

 Burgess of cert"ain species of Thanaos and they have therefore be- 

 come of considerable importance. I wrote to Mr. Samuel 

 Henshaw asking if he knew where they were,^ also to Mr. Charles 

 W. Johnson^ and Dr. L. 0. Howard.'* 



* "Museum of Comparative Zoology, Cambridge, Mass., Oct. 4, 1913. 

 Scudder's microscopic slides were in considerable confusion when received 

 at the Museum but I have at last searched without however finding any that 

 can be considered types of any of the species described by Scudder Burgess. 

 I have also asked Burgess's brother thinking that the chance of any in the 

 hands of the family should not be overlooked and here again I was disap- 

 pointed. The only source I can think of is the Boston Society of Natural 

 History. They have or had a microscopic collection and Burgess may have 

 given them to the Society. Johnson should be able to let you know. I do not 

 believe there is any chance of finding them in the U. S. National Museum 

 though Burgess sold his Diptera to the Museum when Riley had charge and 

 he may have included material other than Diptera." 



3 "Boston Society of Natural History, Oct. 13, 1913. 

 I have looked over all of our microscopic slides and can find none that 

 pertain to the Scudder-Burgess article on the genitalia of Thanaos." 



* "All the likely men have been consulted and search has been made, and 

 the genitalia of Thanaos from the Scudder-Burgess types cannot be found. 

 It is the recollection of both Mr. Schwarz and myself (and we were both here 

 at the time) that the Burgess collection bought by Professor Riley contained 

 only Diptera." 



