i2 4 POPULAR SCIENCE MONTHLY 



the species, of course, are supposed to agree with living ones ; but most 

 of the genera agree well, except in certain groups, like the plant lice, 

 in which there is a similar divergence throughout. 



Owing to this singular constancy of fundamental structure, we are 

 able to ascertain that some striking types now confined to particular 

 parts of the world, were once very widely spread. 



Perhaps the most remarkable instance of this sort is afforded by the 

 tsetse fly, Glossina. Scudder obtained from Florissant an imperfect 

 specimen of a large fly, which he regarded as representing a new genus 

 and species. We were so fortunate as to secure a much better example, 

 showing the long proboscis, and it was not difficult to recognize it as a 

 veritable tsetse fly. The species, of course, is extinct ; but the genus is 

 the same as that now confined to Africa, where it is dreaded as the 

 disseminator of some of the most terrible diseases known. What part 

 the existence of such flies may have played in the destruction of the 

 Tertiary mammalia we can only surmise; but it is not impossible that 

 their influence was great. How it happened that they disappeared 

 entirely from America and survived only on the Ethiopian continent 

 is, of course, unknown. 



Another discovery, hardly less interesting, was a species of Neurop- 

 tera belonging to the family Nemopteridse. These insects are very 

 fragile and delicate, somewhat dragon-fly-like in form, but with the 

 most extraordinary hind wings — consisting of a long narrow stalk, 

 with a dark-fiddle-shaped expansion at the end. One species of this 

 family has been found in Chile, while others are known from the 

 warmer parts of the old world. The whole group has become extinct 

 in North America, but the fossil proves that it once existed there. Such 

 a fossil as this not merely throws a flood of light on the past migrations 

 of a peculiar group, but is the first and only indication we have of the 

 past history of its race. 



Florissant is famous for its fossil butterflies, having nearly half 

 of the number known in that condition. My wife was particularly 

 anxious to find a fossil butterfly, and often as we went out to work, we 

 asked, would this be the day to yield the coveted treasure? Yet all 

 the first season passed, and no butterfly was obtained. Toward the 

 close of the second season, however, my wife sat down one day at a new 

 place, to see what it might be worth. She had scarcely begun to turn 

 ever the shale when, behold, a truly magnificent specimen ! It showed 

 the upper wings, the body and one antenna, the spotting still plainly 

 visible upon the wings. It proved to be an undescribed species, but 

 of a genus still existing in Colorado, though more common southward. 

 When compared with the Scudder collection, it was seen to be the 

 second finest of the butterflies, yielding place only to Scudder's in- 



