COLORADO A MILLION YEARS AGO 



449 



laid down before this event, but after 

 that, we have then a rehitive date to use 

 in our studies of stratigraphy. Forward 

 evolution among the plants and insects 

 during the last million years or so has 

 been extremely slow, or perhaps in most 

 groups altogether lacking; but migra- 

 tions have been many, and from these 

 we may date our rocks and connect the 

 presence of fossils with changes of land 

 and water. 



Among the Florissant insects, perhaps 

 the most interesting are two species of 

 tsetse fly {Glossina), a genus now wholly 

 absent from the New World, but well 

 known in Africa, where certain species 

 carry disease-producing Protozoa. Sleep- 

 ing sickness in man results from the bite 

 of tsetse flies infected with a certain 

 trypanosome. Whether the Miocene 

 species of Glossina carried any organisms 

 producing disease we cannot now deter- 

 mine, but it is not unlikely. Professor 

 H. F. Osborn had written concerning 

 the probable reasons for the extinction 

 of so many of the large American mam- 

 mals, and had cited the tsetse fly dis- 

 eases in illustration of possible causes. 

 By a curious coincidence, the tsetse fly 

 was discovered at Florissant shortly 

 ■ after the publication of these suggestions, 

 affording such measure of confirmation 

 as could in the nature of the case be 

 expected. The second species of fossil 

 Glossina, found later, was named G. 

 oshorni in commemoration of this coin- 

 cidence. 



Florissant is famous for its fossil 

 flowers, and equally for the flower- visit- 

 ing insects, bees and butterflies. All the 

 New World fossil butterflies are from 

 Florissant, and some of them show the 

 bands or spots upon the wings very 

 perfectly. The finest of all was obtained 

 by Scudder, and is in the Museum of 

 Comparative Zoology at Harvard Uni- 

 versity. A very good one, lacking the 



lower wings, was found by Mrs. Cocker- 

 ell. Moths, for some reason not ex- 

 plained, are extremely scarce, and usu- 

 ally poorly preserved. A very good 

 caterpillar has been found. Beetles 

 are very abundant, and including those 

 lately published by Professor Wickham, 

 now number five hundred and fifteen. 

 To these will be added thirty-nine 

 species of Elateridse, which Professor 

 Wickham has described in manuscript. 

 While the beetle fauna shows much in 

 common with that of today, the absence 

 of certain groups is no less remarkable 

 than the great abundance of others, 

 especially of the weevils. 



The plants, better than the insects, 

 indicate a milder climate than exists in 

 Colorado today, and especially a moister 

 one. There were no palms, but great 

 redwoods mingled with figs, magnolias, 

 Ailanthus, Sapindus, elm, beech, walnut, 

 chestnut, incense cedar, maples, pop- 

 lars, pines, and oaks; a mixed forest con- 

 sisting of elements which cannot be found 

 together in any one place today. Nearly 

 all the plants are very closely allied to 

 living ones, in some cases so closely, that 

 but for the interval of time we might 

 well regard them as mere varieties. Sev- 

 eral species are said to belong to the 

 family Proteacese, and although this ref- 

 erence has been disputed, it appears 

 to be correct. Certainly they are quite 

 unlike any components of the present 

 North American flora, while some of 

 them, at least, are extraordinarily like 

 certain proteaceous species. 



On one occasion I led my wife up to 

 some young plants of Grevillea robusta in 

 a greenhouse, and asked without any 

 explanation, "Where have you seen 

 that?" The reply came instantly: "In 

 the shale." She did not know why I 

 asked, nor what the plants were; the 

 impression made by the cut of the leaves 

 was naive and immediate. The fossil 



