1917] Fossil Insects 11 



still ahead. The parallel is of course not exact, since insect 

 genera are much more stable and long lived than those of 

 mammals. 



The fauna of Prussian Amber, of Oligocene age, is extraordi- 

 narily rich and beautifully preserved, the specimens resembling 

 mounts in Canada balsam. In the museum at Konigsberg are 

 over 100,000 specimens, while many exist elsewhere. Fake speci- 

 mens are occasionally seen in collections, or specimens supposed 

 to be in amber, but really in African Copal, of post-tertiary 

 age. Putting aside all these, the perfectly genuine Oligocene 

 amber collections are enormous, though only partly worked 

 up. Ulmer, in a most remarkable work, has monographed 

 the Trichoptera; Wheeler has done a like service for the ants; 

 Meunier has described a great series of Diptera, and other 

 authors have discussed smaller groups. Edmund Reitter 

 has made a preliminary survey of the Coleoptera, indicating 

 the recognisable families and genera, and a considerable number 

 of apparently new genera not yet described or named. On 

 looking over the lists, one notices first of all the richness of the 

 fauna, the great abundance of genera and species. During 

 mid-Tertiary times, the climate of the present Holarctic region 

 was warmer than at present, and conditions seem to have 

 been exceptionally favorable for an abundance of insect life. 

 Since that time, the glacial period, or rather succession of 

 glacial periods, has destroyed or driven out very many types, so 

 that today we dwell in a relatively impoverished world, so far 

 as the North Temperate region is concerned. Another remark- 

 able thing is the lack of progress exhibited in the two million 

 years or so since the time of the amber. Wheeler, referring 

 to the ants, says that since the amber "the family has not only 

 failed to exhibit any considerable taxonomic or ethological 

 progress, but has instead, suffered a great decline in the number 

 of species and therefore also in the variety of its instincts, at 

 least in Europe." Ulmer, speaking of the Trichoptera, says 

 that the amber fauna is quite as highly developed as that of 

 modern times. The presence of numerous extinct genera 

 in all groups bears witness rather to the faunal contraction 

 already mentioned than to any uniform and general advance 

 of organization. There are, indeed, some archaic genera, 

 but such also exist today. It must be said, however, that 

 the bees, which I have studied, all belong to extinct genera, and 



