76 Bulletin of the Brooklyn Entomological Society Vol. XVI 



times lacking, and that the thoracic marks of those on the pop- 

 lars were never less than two rather large triangular basal spots 

 with a small central spot between, these sometimes coalesced and 

 extended to the apical margin forming a solid black discal area, 

 in which case an additional small black spot appears in the pale 

 apico-marginal portion. This led to the conclusion that there 

 might be two species. The poplars and willows in the meadow 

 were closely mixed, and the writer studied the beetles with great 

 care during two summers, but failed to note a single instance of 

 either form occurring on the food plant of the other. 



The writer has identified the beetles as Phytodecta affinis 

 Gyll. — the willow beetle of which arcticus Mann, is said to be a 

 variety — and Phytodecta (Spartophila) pallidus Linn. — the pop- 

 lar beetle. In the Junk Catalogus they are placed in different 

 subgenera, distinguished by a slight difference in the prominence 

 of the tooth at the apex of the front tibiae and the number of the 

 thoracic setae. 



Thorax with setae at the posterior angles only. All the 

 tibiae strongly toothed at apex Phytodecta. 



Thorax with setae at anterior and posterior angles. Ante- 

 rior tibiae scarcely toothed at apex Spartophila. 



(Kuhnt, Illus. Bes. Tab. Kaf. Deuts., p. 848.) 



Drawings of the oedagus of these and the other species of the 

 genus are given in a plate published in the Deiutsche Entomo- 

 logische Zeitschrift. (XXX, 1886, p. 26, taf. I. ff. 42, 47.) The 

 writer has dissected the oedagus from males of the two species 

 and finds them in accord with the drawings. There is consider- 

 able difference in the form. In affinis the oedagus is slender and 

 rather acuminate ; in pallidus it is larger at the apex and broadly 

 rounded. 



The eggs of the beetles are laid in clusters on the leaves of the 

 food plant and the larvae in their early stages feed in groups. 

 Several of these groups were raised to maturity. Those of the 

 poplar beetle — pallidus — exhibited nothing worthy of special note. 

 A group of eight raised on willow were remarkable in that the 

 thoracic marking of four of the specimens was that of the poplar 

 beetle, pallidus, the others being typical affinis. The eight indi- 



