INJURIES TO APPEARANCE OF TREES. 
19 
finally covered by wood and bark. Until this process is completed, 
the tree is disfigured by pits with dead bark and wood at the bottom, 
and even when completely healed, the spot remains a source of weak- 
ness. In fact, all sapsucker pecking is followed by more or less 
rotting and consequent weakening of the wood, and renders trees 
more liable to be broken by the wind or other causes. 
Sapsucker injuries usually stimulate growth of the wood layers at 
the points attacked, so that they become much thicker than usual. 
Tins results in a slight swelling of the bark, and when the birds reopen 
the old wounds year after year, as they habitually do, succeeding 
wood layers make excess growth and in ^^^^^ 
time shelflike girdles develop. On trees 
having thin, flexible, rapidly growing 
bark, the swollen girdles are smoothly 
covered and rounded (fig. o; PI. IV. fig. 
3), but on trees having thick, brittle, or 
stiff bark, the bark breaks and a gaping 
furrow is formed at the summit of the 
swelling (PL VII, figs. 2 and 3; PI. VIII. 
fig. 1 ; PL IX, fig. 2; PL X, fig. 1). Some 
trees are remarkably deformed by such 
protruding girdles (fig. 5.) 
Buds are apt to start from the edges 
of holes drilled by sapsuckers and form 
twigs or small branches. Such shoots 
have been noted on honey locusts and 
sycamores, and in some trees, such as 
willows and elms, which are prone to 
produce adventitious buds, the}' arise 
from sapsucker injuries in such numbers 
as to materially disfigure the trees. 
The bark may be otherwise disfigured, 
as by exudations of gum or by pitch 
streams, or sapsucker injury may be fol- 
lowed by fungus attack, as in certain 
pines. Spores of Peridermium cerebrum sometimes reach the wood 
through sapsucker punctures and cause knotty gall-like outgrowths 
which greatly disfigure the trees. 
The wood also is often distorted and discolored in such a way as to 
destroy its commercial value. This phase of damage by sapsuckers 
is exceedingly important and will be made the subject of a separate 
section of the bulletin. 
Fig. 5.— Sapsucker work on honey locust 
(Gleditsia triacanthos). Protruding gir- 
dles. Specimen is IS inches in diameter. 
