24 



of Columbia it has been rather extensively infested by a plant louse 

 (iSiphonophora liriodendri), but although the lice occur on the leaves 

 in great numbers, the general appearance of the trees has not suffered. 

 There is a little gall midge which produces little black spots on the 

 tulip tree leaves and disfigures them to some extent, and quite recently 

 Mr. Schwarz has found that tulip scrub is affected to some extent in 

 the District of Columbia by a little bark-boring beetle. 



The box elder is a singularly unfortunate choice for a shade tree in 

 this climate. It is almost defoliated by the webworm, it is sought 

 after by the tussock moth, and various leaf-rollers attack it as well as 



certain destructive borers. 

 In the West the box-elder 

 plant-bug (Leptocoris trivit- 

 tatus) breeds upon it in 

 enormous numbers, and not 

 only damages the trees to a 

 serious extent, but causes 

 much further annoyance by 

 entering houses for hiber- 

 nation. 



The European elm is given 

 a low rank, almost entirely 

 on account of its annual de- 

 foliation by the imported 

 elm leaf-beetle. 



The honey locust and the 

 black locust, while not defo 

 liated to the same extent ar 

 many other trees by the web- 

 worm and the tussock-moth 

 caterpillar, are rendered 

 very unsightly almost every 

 year by the work of a leaf- 

 mining Hispid beetle and of 

 certain Lepidopterous leaf 

 miners. They are also fre- 

 quently killed by the large Lepidopterous borer, Xyleutes robinice, and 

 certain Coleopterous borers also infest them. 



From the insect standpoint, there are several fine-growing orna- 

 mental trees on the grounds of the Department of Agriculture, not 

 listed above, which are seldom attacked by insects. The beeches, 

 hornbeams, alders, and magnolias have very few insect enemies, and 

 are rarely defoliated by either of the principal leaf-eating caterpillars. 

 With regard to the extreme attractiveness which the European elm 

 possesses for the imported elm leaf beetle, the question is frequently 

 asked whether it would not be better to cut down all European elujs 



FIG. 9 Fall webworm (Ryphantria cunea), 

 cocoons natural size (original). 



Moths and 



