EXPERIMENT STATION BULLETINS. 



"671 



The anal-plates vary considerably in form but usually the lateral and 

 apical angles are rounded. There are on each side two fringe setae, 

 two sub-apical setae and four apical setae, the latter variably placed. 

 The most common arrangement being three on the dorsal surface near 

 the apex of the plate, forming a triangle, with the fourth seta slightly 

 in front of the other three and on or near the mesal margin of the plate. 

 Sometimes this latter seta is set well back from the mesal margin on 

 the dorsal surface and sometimes to a lesser distance on the ventral 

 surface. Sometimes the three that form a triangle are placed on the 

 margin and more rarel^^ near the edge on the ventral surface. 



Figure 7. 



Lccanium cornl on maple. — Antenna; spiracular 

 setae ; and ventral view of anal-plates ; f , fringe 

 setae; sa, sub-apical setae; a, apical setae, the last 

 named on dorsal surface. 



There are clusters of gland-pores near the spiracular setae and often 

 large clusters cephalad of the anal-plates. Often strings of these round 

 gland-pores extend from the spiracular setae to the spiracles. These seem 

 especially numerous in specimens collected on Basswood and on Bitter- 

 sweet, also on those collected on Ash, Hawthorn, Cornus and White 

 Oak. These gland-pores are most conspicuous in young specimens: 

 Sometimes they almost disappear as the derm thickens with age. 



The chitinized derm shows many pores appearing as transparent 

 irregular openings in the chitin usually arranged somewhat radially. 



