194 



THYSANOPTERA AND ORTHOPTERA. 



TABLE I. — Showing the number of thrips in flowers near a road and in simi- 

 lar flowers some distance from the road. 



It seems evident from the figures that thrips were generally more 

 abundant near a road than at some distance from it. I have noticed 

 this to be true in many cases where I did not count the individuals. 

 For example, I collected from nearly two hundred heads of an undeter- 

 mined species of thistle extending in a continuous line along a ditch, 

 from a well traveled public highway back into the fields. No two 

 successive plants were more than about six feet "apart. I would esti- 

 mate that thrips were about twice as abundant near the road as at a 

 distance of 70 yards from it. These thrips were exclusively Euthrips 

 tritici, those of Table I were principally of this species. The same 

 relative abundance of thrips near roads was noticed in a number of 

 other instances, and in no case, apparently, were there fewer near the 

 road than in similar situations farther from it. 



If this variation in the abundance of thrips in different localities is 

 really due to a lack of a tendency to migrate, as I have supposed, in- 

 teresting information regarding the rapidity of their dissemination may 

 be gained by noting how rapidly the numbers of thrips diminish in ])ass- 

 ing from the point of greatest abundance. Individuals were counted 

 in a number of places at different distances from a road. The same 



