NOV., '09] ENTOMOLOGICAL NEWS 375 



It is a remarkable fact that while over 90 per cent, of the 

 species found in this country are new, yet only two genera 

 are peculiar to this country. The American fauna differs 

 from that of the old world also in the much greater percentage 

 of smooth species. In this country at least 70 per cent, of the 

 species have a smooth, shiny integument, while in the old 

 world the numbers of smooth and of rough or sculptured 

 species are almost equal. The causes for this difference are 

 not known. Here are some suggestions which may possibly 

 account for such an apparent difference in the faunae of the 

 two continents. 



i. That the shiny species are much more easily seen be- 

 cause of their reflection of light from the surface of the in- 

 tegument, and that a more complete search in this country 

 will reveal many more rough species here. 



2. That there is something peculiar or favorable in our 

 climate or in the vegetation upon which the mites feed that 

 causes a larger percentage of smooth species. 



3. That most of the shiny species were originally indigen- 

 ous to this country and that most of the species that there are 

 in Europe of this kind have been largely introduced from 

 America, where the shiny species, or some of the most im- 

 portant genera including these species, have had a long con- 

 tinued history and consequently a greater chance for the 

 production of new species. 



Jn regard to the first factor there is but little doubt but that 

 it plays an important part in the apparent difference of our 

 fauna from that of Europe. I have found that in the ca>c 

 of my collection that it was over a year before I discovered 

 a single rough species. Since that time a careful watch and 

 search has revealed nearly two dozen of these. 



In regard to the second cause, little is known as present due 

 to our unfamiliarity with their food habits. 



The third mentioned cause has some evidence in its sup- 

 port for it is true that the increased percentage of smooth 

 species in this country is largely due to the large number of 

 the abdominal-winged forms here, which already number over 

 40 species. 



