AVitli this group we reacli the most important section of the present 

 work, since it of all the lower orders of insects was far the most abmidant 

 at Florissant. As, however, the group is divisible into two great suborders 

 under which, separately, such general statements as seem appropriate regard- 

 ing the relative representation of the families will be given, we reserve here 

 only a brief remark or two upon the relation of the two suborders. 



I presume it can not be far wrong to state that the homopterous fauna 

 of any given region of considerable extent in the north temperate zone is to 

 the heteropterous fauna as about one to three, or, in other words, that about 

 25 i^er cent of the hemipterous fauna is homopterous. These figures are 

 the result of the comparisons of several faunal lists. In Mr. Uhler's List of 

 the Hemiptera of the United States west of the Mississippi (the geographical 

 area of our present work), the Homoptera hold a still more insignificant 

 place, forming scarcely more than 13 per cent of the Avhole. In tropical 

 countries a ver}- different proportion obtains, the Homoptera holding, or 

 nearly holding, their own beside the Heteroptera, and subtrojaical countries 

 or those which feel the direct influence of their proximity show an inter- 

 mediate position ; thus in Berg's Enumeration of the Argentine Hemiptera 

 the proportion of the Homoptera to the whole is almost exactly 30 per cent 

 Now, it is precisely this proportion, 40:93, or 30 per cent, which Heer found, 

 the fossil Homoptera to hold in his first essay on the fossil Hemiptera of 

 Oeningen and Eadoboj. A careful enumeration of the fossil Hemiptera of 

 Europe to-day gives the Homoptera 34 per cent of the whole fauna ; but, if 

 those from the amber (which greatl}' heighten the projiortion of Homoptera) 

 be excluded and we reckon those of the rocks only, the Homoptera have 27 

 per cent. On the other hand, if we take only the fiiuna of the Oligocene of 

 Europe, including the amber, the proportion of the Homoptera amounts to 

 41 per cent. This clearly indicates an approach to tropical relations. Our 

 own Tertiary fauna is almost exclusively Oligocene, and has been found in a 



