6 
BULLETIN 116. 
/ 
for new things, for Mr. Piper states that it is n6t found abundantly on 
the native maples, but infests currant, gooseberry, plum, pear, haw- 
thorne, mountain ash, Lombardy poplar, weeping willow, currants 
{Ribes sanguinum) , and species of willow (Salix flavescens and S. lanadrd). 
A careful study of the forms on all of these food plants has not 
been made and it will be wise to make a mental reservation as to the 
identity of the species in some cases until further evidence is forth¬ 
coming. 
The economic history of the insect shows that its destructive 
abundance in certain localities is periodic. The data at hand fail to 
show that this periodicity is amenable to any law, though there have 
been two periods of general abundance over its range. The statement 
has been widely circulated that the scale is seldom injuriously abundant 
two years in succession, but this has been proved to be untrue within 
the past few years in widely separated localities. In the early eighties 
there was a general visitation of the pest and Dr. Forbes 'made a num¬ 
ber of preliminary experiments looking toward control. On this occa¬ 
sion the insects appeared in great abundance in 1880 and 1884, subsid¬ 
ing to insignificant numbers during the intervening years. A second 
scourge occurred during the past five years and is reported by Mr. 
Chittenden as being more generally abundant over its range than at 
any previous year. The city parks of Denver and Chicago seem to be 
the storm centers. In the latter place the lower limbs of the silver 
maples have been killed in great numbers, leaving the trees unshapely 
in appearance. Many hundreds of trees have been killed outright. 
In Denver the destruction has been, perhaps, less severe, but weeks 
were spent cleaning dead limbs out of the parks and many trees along 
the more crowded streets have been injured to such an extent that they 
are practically worthless. 
LIFE HISTORY 
When the sap begins to flow in the food plant the young hiber¬ 
nating females begin to suck up the fluid rapidly and to grow. In a 
few weeks they have increased their size about four times. At this 
stage the scales, which before may have been unnoticed because of 
their flat position on the bark and similarity to it in color, become 
suddenly conspicuous on account of the white cottony mass of wax 
which is thrust out from under the posterior end. This mater¬ 
ial is, composed of wax threads spun from the ventral glands of 
the animal, especially those located on the margins, and serves 
as an ovisac. (See Fig. 2.) The quantity is enormous for the 
size of the insect. The extrusion of it gradually raises her body 
from its flat position on the twig until it stands out at an angle of some 
sixty degrees or even vertically. During this period the egg laying 
proceeds. This takes place at different times in different localities 
and seasons, varying with the temperature and in some cases with the 
food plants. In Florida when thi^ scale appears on pecans, Gossard 
states that the ovisacs become conspicuous during April and May. In 
most other places they appear in May or June. 
