26 



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

 {Siphonophora Uriodendri), 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 tri- 

 vittatus) 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 

 hibernation. 



The European elm is 

 given a low rank, almost 

 entirely on account of its 

 annual defoliation by the 

 imported elm leaf-beetle. 

 The honey locust and the 

 black locust, while not de- 

 foliated to the same extent 

 as many other trees by the 

 webworm and the tussock- 

 moth caterpillar, are ren- 

 dered very unsightly al- 

 most every year by the 

 work of a leaf -mining His- 

 pid beetle and of certain 

 Lepidopterous leaf miners. They are also frequently killed by the 

 large Lepidopterous borer, Xyleutes rohinise, 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, horn- 

 beams, 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 elms 



Fig. 9.— Fall webworm {Ilyphantria cunea). Moths and 

 cocoons— natural size (original). 



