BLACK GEAI^-STEM SAWFLY. 



These records probably indicate only approximately the present 

 distribution (fig. 1) of the species. A more extended investigation 

 will be necessary to establish the exact limits. The records are 

 sufficient to establish a probability that it already occurs over the 

 greater part of Virginia, Maryland, Pennsylvania, New Jersey, and 

 Delaware, and it is possible that West Virginia, eastern Ohio, 

 southern Xew York, and even some of the Xew England States may 

 already be included within its range. 



PROBABLE FUTURE DISTRIBUTION IN AMERICA. 



Judging by its wide distribution in the Old World, as well as by 

 the character of localities already included within its range in this 

 country, including both 

 tidewater and mountain 

 districts, there seems little 

 reason to doubt that the 

 species will eventually 

 spread over all the wheat- 

 growing sections of the 

 eastern and central United 

 States. Whether it will 

 accommodate itself to the 

 arid and semiarid wheat- 

 growing districts of the 

 West is matter for specu- 

 lation. The average pre- 

 cipitation of this region 

 does not differ greatly 

 from that of southern 



Russia, where the species seems to be at its worst. The mean 

 temperatures of the two regions probably are not widely differ- 

 ent. It seems possible, therefore, that unless some other climatic 

 or physical factor intervenes, the species may spread eventually from 

 coast to coast. That it will spread northward into Canada may be 

 doubted, since in Europe, although recorded from Sweden, it seems 

 not to occur generally in the colder northern portion. 



FOOD PLANTS. 



FOOD PLANTS IN EUROPE. 



In European literature, with one exception, the records of food 

 plants of Trachelus tabidus are by Eussian entomologists. Endow 

 (43), in speaking of Cephus satyrus Panzer, C. nigrinus Thomson, G. 

 pallipes Klug, C. arundinis Giraud, and C. tabidus Fabricius, makes 

 the general statement that in southern Europe these species live in 



Fig. 1. 



-Present known distribution of Trachelus 

 tabidus in America. 



