310 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54; 



There is only one exception to the rule that these flies are peculiar 

 to the African Continent ; G. tachinoides has been found in southern 

 Arabia, as recorded by Captain R. Markham Carter in 1906. 



In 1892 (Bull. U. S. Geol. Survey, No. 93) S. H. Scudder described 

 a remarkable fossil fly from the miocene shales of Florissant, Colorado, 

 at that time supposed to be of oligocene age. He considered it to 

 belong to the Oestridae, which contains the bot-flies and warble-flies. 

 The head was unfortunately missing, but Scudder correctly noted 

 the singular course of the fourth vein, which found no counterpart 

 among living Oestrids. It naturally never occurred to him to compare 

 the insect with an African genus, so he described it as a new genus and 

 species, Paloestrus oligocenus. In 1907 Mr. Geo. N. Rohwer found 

 a good specimen of this species at Florissant, showing the proboscis, 

 and I was able to determine without difficulty that it was a genuine 

 tsetse fly, astonishing as that might seem. An enlarged figure ap- 

 peared in the Popular Science Monthly (August, 1908, p. 117). A 

 figure was also published by Bland-Sutton in the Middlesex Hospital 

 Journal (London) for December, 1907. Mr. E. E. Austen, of the 

 British Museum, the principal authority on tsetse flies, quite agreed 

 with the reference of the fossil to Olosftina. 



Thus it appeared that a million years ago, more or less, tsetse flies 

 inhabited Colorado. Prof. Henry F. Osborn had shortly before dis- 

 cussed the possible causes of the disappearance of so many large 

 mammals which formerly inhabited America, and had suggested that 

 there might have been some flies carrying disease-producing organ- 

 isms, such as the tsetse fly. If at various times and places such dis- 

 eases as the nagana invaded the herds of Tertiary horses and other 

 animals, these creatures might abruptly disappear, leaving no trace 

 of the cause of the phenomenon. It is naturally out of the question 

 to determine whether these ancient species of Glossina did actually 

 carry trypanosomes, but their occurrence in the shales is certainly 

 suggestive. 



In 1909 I had occasion to describe a second species of tsetse fly 

 from the Florissant fossil-beds, and named it Glossina oshorni. It 

 was published in Nature for April 1 of that year (p. 128). 



In 1916 Mr. George Wilson was so fortunate as to find two addi- 

 tional specimens of Glossina at Florissant, representing additional 

 species. The specimens are now in the United States National Mu- 

 seum. One of them, Glossina veterna Cockerell (Nature. Sept. 28, 

 1916, p. 70) is a truly marvelous specimen, showing not only the 

 proboscis, wings, and body, but even the characteristic hairs on the 

 body. The accompanying plate, kindly made by Dr. R. S. Bassler, 

 shows it enlarged. It is actually 12.5 mm. long, the wings 10.9 mm. 



The other species, which I have named Glossina armatij^es, is not 

 so well preserved, but its salient characters can be made out. The 



