12 Annals Entomological Society of America [Vol. X, 



on the whole are distinctly less advanced than the higher modern 

 ones. There are, however, many modern genera of bees more 

 primitive than any yet found in amber. Meunier's catalogue 

 of amber Diptera is remarkable for the great numbers of 

 Tipulidae, Cecidomyiidas, Mycetophilidae, Chironomidae, Psych- 

 odidae, Phoridae, Empididae, and Dolichopodidae. On the other 

 hand, Asilidas, Bombyliidae, and many families of higher Diptera 

 are very rare or absent. This looks at first like a certain 

 indication of the relatively undeveloped character of the 

 Dipterous fauna of the Oligocene, and is quite in line with the 

 evidence from the much earlier Eocene of North America. 



It will be noted, however, that precisely those forms are 

 present which would most easily and probably be caught in the 

 amber, and there is no possible doubt that the list fails to 

 represent large elements in the fauna. This is well shown by 

 the scarcity of Lepidoptera, which undoubtedly abounded in 

 those days. The Florissant Coleoptera, of Miocene age, 

 much later than the Baltic amber, are remarkable for the 

 prevailingly small size of the species, and here we cannot so 

 easily ascribe the peculiarity to the method of preservation. 

 It would doubtless be true, under almost any conditions, 

 that the larger and stronger forms would be most likely to 

 escape the destructive influence; yet we are left with a residue 

 of feeling that the average size of the insects actually was less 

 than at present. Many of the larger species in the present 

 fauna represent essentially southern, or even tropical groups, 

 and it may well be -believed that though their ancestors existed 

 in Oligocene and Miocene times, they had not yet spread 

 northwards. The very impoverishment of the fauna during 

 glacial times, with the subsequent amelioration of the climate, 

 may have given opportunities to southern types, which during 

 the mid-Tertiary were barred out by an already rich and 

 aggressive fauna occupying the territory. 



Also Oligocene, but perhaps later than the amber, is the rich 

 deposit at Gurnet Bay, in the Isle of Wight. The specimens are 

 preserved in solidified mud, absolutely without compression. 

 The materials are of particular importance, not only as coming 

 from a distinct locality, but on account of the quite different 

 medium in which they are preserved. So far, 25 Diptera, 4 

 dragon flies, 8 ants, 1 Diapriid, 1 wasp, 4 Homopteron, 1 Lep- 

 idopteron, 2 termites, a Sisyra, a Raphidia and an Aeolothrips 



