THE EUROPEAN ELM SCALE IN THE WEST. Bs) 
other ants are known to transport scale insects from one tree to 
another in order to increase their food supply, and this method of 
transportation probably applies to this species as well as to others, 
since it is usually attended by a great many ants. Elms are nearly 
always planted so close that some of their branches interlace, en- 
abling the larve to crawl at will from one tree to another. Thus 
it is not long before 
the European elm scale 
has thoroughly — estab- 
lished itself upon most 
of the elms in a locality. 
INJURY. 
Thousands of these 
scale insects sucking 
the plant juices from 
the leaves, twigs, and 
branches (figs. 2, 3) 
cause considerable in- 
jury toelm trees. Their 
effect upon the elm is 
shown by yellowing and 
premature dropping of 
the leaves, stunting of 
growth, and dying twigs, 
branches, and entire 
trees. Their injury is 
most apparent on young 
trees, which occasionally 
they kill. Mature trees 
are seldom killed. 
A less serious trouble 
is the production of a 
considerable amount of 
honeydew. which covers 
the leaves, twigs, and 
branches, making them 
black and sticky. It also 
drops on the street and 
sidewalk, making the 
pavement slippery and ; : 7 
dangerous to passing ve- "%* 2—Adwlt females of European elm scale on elm 
hicles, besides having an 3 
unpleasant appearance and odor. Many disagreeable insects are 
attracted by the honeydew. 
In some sections the American elm is reported as the favorite 
host of the European elm scale, while in other localities the English, 
Camperdown, or slippery elm is reported to be the favorite. The 
American and Camperdown elms seem to be preferred by it in Cali- 
fornia. Probably the degree of infestation depends upon the con- 
dition of the tree more than upon any other factor. 
