12 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



encing native species. Professor Webster is referring to intro- 

 duced species. In that case a trend is to be considered. Too 

 much stress has been laid on circumpolar faunae. It is more 

 natural to consider that insects have come up to us through 

 geologic periods and palaeontology gives us some knowledge of 

 this. We must consider rather that it was similar climates 

 producing similar species both in Europe and America due to 

 this similar climate causing parallel development. 



Mr. Knab said that climate was of more importance than 

 plant distribution in considering the distribution of insects, 

 and cited as an example the species of the genus Melasoma in 

 North America which have gone under the name of M. lap- 

 ponica. There are three distinct forms related to lapponica 

 in the United States, the first occupying the region from 

 Alaska to California, the second the Great Lakes region to 

 New England, and the third the South Atlantic States and 

 Middle West, northward to the lakes. Their food plants, 

 the willows, however, go south to Patagonia, but the species 

 of this group fade out to the south and do not occur in Mex- 

 ico. They are closely related to forms occurring in Europe and 

 Siberia and are clearly of circumpolar origin. In order to 

 understand our own Southwest we must know more of the pla- 

 teau region of Mexico, which is a flat, dismal region. The 

 only part of Mexico that is well explored is the slope and the 

 low coast region in the state of Vera Cruz, but the table-land is 

 not -touched. 



Dr. Howard stated that the grasses were unimportant on 

 the table-land. 



Mr. Schwarz said that on the table-lands of Mexico there are 

 three itnpoitant factors in the flora: the cacti, the mesquite, 

 and the grasses. In the state of Durango grass is important. 

 The fauna and flora of the table-lands was found by Mr. 

 Schwarz to extend almost to the City of Mexico and probably 

 goes further. The fauna of the plateau region is separated 

 from the tropical fauna by a sharply defined line. Under 

 the name Tropics are mixed up a lot of elements. The forest 

 region of Tampico is similar to that of Florida and Cuba, but 

 not like that of eastern Guatemala. 



