6 bulletin: museum of comparative zoology. 



pigmental colors and the preservation of microscopic structures like 

 wing hairs with such wonderful perfection. 



The distribution of the Miocene parasitic Hymenoptera among the 

 various groups is very interesting and I have attempted to represent 

 graphically in the accompanying diagram (Plate 1) the comparative 

 abundance of the several families and smaller groups during Recent, 

 Miocene, and Oligocene times. In order to make the diagram more 

 easily understood, the comparative numbers and not the actual ones 

 are shown by the width of the black lines for each period since the 

 numbers of species known vary much in proportion for the three 

 periods. 1 



Only one family, the Ichneumonidae, was proportionately more 

 abundant in Miocene times than at present and its abundance was 

 caused entirely by the occurrence of a much larger number of species 

 in two of its subfamilies, the Ophioninae and Pimplinae; the other 

 three subfamilies, Ichneumoninae, Cryptinae, and Tryphoninae were 

 about as well represented then as now. The Braconidae appear to 

 have become less numerous, and I believe the change has been even 

 greater than is shown by the diagram, since fossil Braconidae are 

 usually more poorly preserved than the Ichneumonidae, due probably 

 to their softer bodies and wings. The Evaniidae appear to have 

 become less abundant in recent times, but this may possibly be due to 

 the small number of species on which the calculation is based. The 

 Chalcidoidea (exclusive of the Mymaridae which are omitted on 

 account of their disproportionate abundance in amber) seem to be on 

 the ascendent, but the number of species of Proetotrypoidea and 

 Cynipoidea is so small that they do not furnish a satisfactory basis for 

 any deductions of this nature. 



I have not been able to find much evidence bearing on the probable 

 relationships of the Florissant fauna from a study of the Parasitic 

 Hymenoptera. This is disappointing, but really to be expected, for 

 the group, with minor exceptions, is very widely distributed at the 

 present time and extremely similar the World over. A few points of 

 interest may however be worthy of review. The occurrence of a fig 

 insect shows a tropical element in the fauna, but only serves to 

 strengthen the evidence offered by the presence of fossil fig leaves in 

 the flora. Australian and South African affinities are suggested by 



1 1 have used as a basis for the number of recent species, Cresson's Catalogue of 

 North American Hymenoptera. It is now rather old, but I think the proportion of species 

 to be placed in the several families has not changed materially since the time of its pub- 

 lication. 



