38 THE SAN JOSE SCALE. 
if not entirely exempt. This holds, also, to a less extent with the 
different varieties of other fruits. Professor Smith says of plums that 
apparently Japanese varieties are favorites, while those of American 
and European origin suffer much less. The notable exceptions are, 
however, found in the case of pears. This is strikingly exhibited with 
the Leconte and Kieffer varieties, which are almost exempt. 1 A notable 
instance of the latter is the case of a tree which bore both Lawson and 
Kieffer grafts. The Lawson branch, leaves and fruit, was entirely cov- 
ered, while the Kieffer portion was entirely free from the scale. No 
other variety of pear has been found equal to the Leconte and Kieffer 
in immunity. The following list of food plants is substantially as com- 
piled by Dr. Lintner : 
Tiliaceas : 
Linden. 
Saxifragacea : 
Gooseberry. 
Celastracea' : 
Euonymus. 
Rosacea' : 
Almond. 
Currant. 
Flowering currant. 
JEienacece: 
Persimmon. 
Peach. 
Apricot. 
Plum. 
Leguminosea' : 
Acacia. 
Urticacea' : 
Cherry. 
Spiraea. 
Raspberry. 
Rose. 
Elm. 
Osage orange. 
Juglandacece : 
English walnut. 
Hawthorn. 
Pecan. 
Cotoneaster. 
Betulacece : 
Pear. 
Alder .' 
Apple. 
Salicacece: 
Quince. 
Flowering quince. 
Weeping willow. 
Laurel-leaved Avillow (from Asia) 
LIFE HISTORY. 
In common with all the armored scales, the life round of this insect, 
with the exception of a few hours of active larval existence and an 
equally brief winged existence in the case of the mature male, is passed 
under the protection of a waxy scale. This scale covering conceals 
the real insect beneath and prevents any easy observation or study of 
its life history. The San Jose scale has been under most careful 
observation by Mr. Pergande on potted plants in the insectary, and its 
history, which has hitherto been very imperfectly worked out, has been 
thoroughly and carefully elaborated. 
The winter is passed by the nearly full-grown insects under the pro- 
tection of the scale. Early in April in this latitude the hibernating 
males emerge, and by the middle of May the overwintered females 
mature and begin to give birth to a new generation, continuing to pro- 
duce young for a period of upward of six weeks, when they reach the 
limit of production of young and perish. 
1 Mr. Charles Parry has recently obsers ed cases in which both Kieffer and Leconte 
pears have been badly damaged. 
