251 
Pears or branches thickly covered with the Scale occur only on the 
Bartlett and Duchesse d'Angouleme and derived varieties. Such pears 
usually show more or less extended longitudinal cracks, and, at the 
time of my visit, were dropping to the ground by the hundreds. 
The appearance of the Scale on the twigs offers no special features ; 
this year's growth is by far the worst infested, and there are only a few 
trees of which the older branches are infested. 
The two varieties of pear trees just mentioned are the only plants 
where the Scales affect the leaves. Here either one or two or more 
quite regular rows of Scales are along the midrib (on both sides of the, 
same), always on the upper surface of the leaf. On badly infested 
trees there are similar rows of Scales on the side ribs. It was noticed 
that among the Scales on the leaves there are proportionally many 
more male Scales than among those on other parts of the trees. The 
infested leaves do not appear to have the tendency to drop, but their 
color turns to a purplish brown. 
The larvae of the Aspidiotus were very abundant at the time of my 
visit, crawling about with great activity. Among those on the trees 
the tendency is noticeable to proceed to the extremities of the twigs, 
leaves, and fruit. Those crawling about on the ground among the fallen 
pears move considerably slower than those on the trees and certainly 
not in a definite direction. They are seen to ascend the few grasses, 
purslane, and other low plants that come in their way, while others are 
seen to descend again. The bright yellow color of the larvae renders 
them easily visible, and even when still under the mother Scale they 
are so large as to be readily seen with the naked eye. There are 
usually only one or two young larvae under one parent Scale, and since 
no eggs could be found under the many female Scales I examined it 
would appear that the species is viviparous, the larva* hatching gradu- 
ally. The appearance of many infested pears, which are densely and 
evenly covered with the Scales, further suggests that this gradual hatch- 
ing of the larvae has been going on uninterruptedly since several 
months, probably since the time when the fruits commenced to be 
formed ; in other words, that there is in this species no succession of 
generations with definite intervals. 
I failed to find or see a single male, but whether none existed during 
the time of my visit (August 17 and 18) or whether I overlooked them 
can not be decided. 
ENEMIES. 
Whether or not this colony of Aspidiotus perniciosus at Charlottes- 
ville is already infested by parasites was not ascertained during 
my visit. Several badly infested pears were carefully examined, but 
no exit holes of Chalcids were seen on the Scales. Only a few other 
species of insects were seen on the trees, of which only the following 
have any connection with the Scale : Collops 4-maculatus was present 
14161— Xo. 3 4 
