72 THE CANADIAN ENTOMOLOGIST. 



about equal to that of the thorax. The antennae are moderately distant 

 at base. The armature of the thorax will serve to differentiate the 

 Canadian genera thus : — 



Sides of prothorax much rounded and rather suddenly narrowed be- 

 hind, giving a somewhat bell-shaped appearance Orsodachna. 



Sides of thorax with large, distinct tubercle; small s'^tcits.Zeugophora . 



Sides of thorax broadly angulate, more or less distinctly three- 

 toothed ; larger species Syneta. 



Orsodachna, Lair. 



A single species of extreme variability (O. atra, Ahr.^, belongs here. 

 It is common on willow blossoms in spring, several colour-varieties often 

 occurring together on the same tree. All intergrades are known, from 

 entirely blackish individuals, through forms in which the thorax becomes 

 red, with or without a central dark spot, to those with vittate elytra or 

 even of an almost uniform testaceous. From the notes of Dr. Horn, the 

 following key has been constructed as a guide to the best-marked 

 varieties, but it must be borne in mind that numerous intergradations 

 will be met with, not referable to any of these : — 



A. Elytra blackish. 



Thorax blackish, legs dark atra, Ahr. 



Thorax blackish, tibiae and femora testaceous tibialis, Kirby. 



Thorax reddish, with central dark spot luctiiosa, Lee. 



Thorax entirely red hepatica. Say. 



^^5^ Y AA. Elytra vittate or spotted. 



Elytra dark, each with narrow yellow 



stripe vittata. Say. 



mS/ Elytra yellowish, with sutural and lateral dark 



^^^^ stripe trivittata, Lac. 



ll/ Elytra dark, with humeral and apical yellow spot 



fi^ 5_ (Fig. 5) Childrejii, Kirby. 



In general, they agree in these characters : The prothorax is some- 

 what bell-shaped, rather coarsely punctured, less so at the sides ; the 

 elytra are broad at base and with numerous closely placed, rather coarse 

 punctures which show some slight tendency to a serial arrangement. 

 Sides of elytra nearly parallel to about the apical third, whence they are 

 rounded to tip. Length, .16-. 28 in. 



