2 FARMERS’ BULLETIN 723. 
throughout the country, and from their relatively conspicuous appear- 
ance are often detected by observant fruit growers who frequently be- 
lieve them to be the more serious San Jose scale. The oyster-shell and 
scurfy scales, while not dangerous in the sense of generally causing 
the death of infested trees, are, however, of considerable economic 
importance. The complete killing of individual branches of apple 
trees by either species is a matter of frequent observation, and trees 
so badly infested are frequently greatly stunted and retarded in their 
growth, resulting perhaps in extreme cases in the death of the trees. 
Of the two species considered, the oyster-shell scale has been and is 
at the present time the more important. Its mjuries to certain 
shade trees, especially poplar and maple, have been the cause of much 
complaint during recent years. Such shade trees are ordinarily not 
sprayed for scale insects, and the increase of these pests from year to 
year is thus checked only by their natural enemies. The writers 
have frequently seen maple and poplar trees literally incrusted from 
top to bottom with the oyster-shell scale, many of the limbs killed, 
and in rarer instances the trees quite dead, without doubt owing to 
the attack of this scale insect. 
THE OYSTER-SHELL SCALE. 
ORIGIN AND DISTRIBUTION. 
The origin of the oyster-shell scale is a matter of some uncertainty. 
It has a world-wide distribution, and was introduced into the New 
England colonies at an early date. The first American account of 
this insect was written by Enoch Perley in 1794, and in it he stated 
that the pest was doing considerable damage to the apple in Cumber- 
land County, Me. Shortly after 1860 it had reached the Missis- 
sippi River, and at the present time occurs in every State of the 
Union with the possible exception of South Dakota, Oklahoma, and 
Texas. Its occurrence in these States is practically certain, but there _ 
appear to be no records in literature to this effect, and it has not been 
received from these States by the Bureau of Entomology. The insect 
is very troublesome in the Northern States and is especially common 
in the New England States and those bordering the Great Lakes. 
DESCRIPTION AND LIFE HISTORY. 
This insect has received the common name “oyster-shell scale,” 
owing to the resemblance of its scale, or covering, to a long narrow 
oyster shell, as:may be seen by reference to figures 1 and 2. The 
adult female scales are about one-eighth of an inch in length, usually 
brown to dark brown in color, though occasionally they have a grayish 
appearance which is due to bleaching over winter. If present in 
large numbers, for want of room they assume various more or less 
