85 
Wisconsin, and, since the advent of the species upon the Pacific Coast, 
its life-round has been followed by Mr. Kcebele in the hop-yards of 
Oregon and Washington. 
It will be seen from this account that the labor involved in a series 
of observations of this kind, which resulted in the satisfactory ascertain- 
ing of the life-history of but a single species, is something enormous, and 
at the same time I believe that no fault can be found with the methods 
used. 
Where from lack of time, or from other reasons, out-of-door work upon 
plant lice is impossible, good results may be obtained in the insectary, 
provided an abundant supply of the leaves of the food-plant is availa- 
ble. For instance, the present summer Dr. Riley is having a study 
made of the life-history of a species commonly found upon the tulip tree. 
The summer generations are being followed up in this way: To each 
female under observation a glass tube 4 inches long by 1 inch in diam- 
eter is devoted. Every day a large freshly plucked leaf is cut with the 
shears into a square of about 3 inches each way. It is carefully cleaned 
with the brush on both sides, folded into a cylinder and thrust into the 
tube. The Aphidid is carefully removed from the old leaf by means of 
a camel's hair brush and placed within the cylindrical fold of the fresh 
leaf. A stopper of cotton is then thrust in and the tubes as soon 
as prepared are placed in a jar and removed to the basement, where 
they are kept at a constant temperature until the following day, when 
the process is repeated. Extremes of temperature are fatal to the.plant 
lice, and I well remember one hot July day in 1888 when probably 999 
out of every 1,000 plant lice on the shade trees in Washington were 
destroyed by the heat. This operation of removal can not be done, too 
carefully, else the beak will be broken off. The change of food every 
twenty-four hours is absolutely essential, otherwise the drying of the 
leaf holds the beak so that it is impossible to remove the insect. By 
this method the number of young deposited each day and the number 
of molts undergone by each individual may be counted quite as readily 
and in fact a little more so than in the bags on the plants. 
The study of Cocci dae in the insectary is a simple one to the trained 
observer when the food plant can be grown and the insects colonized 
upon it; otherwise it becomes an impossibility, since, after the first 
molt, these insects can not safely be removed from their food. Most of 
the species remain stationary or nearly so, and their location can easily 
be recorded, the exact situation of each individual under observation 
being circumscribed by a ring of ink marked with a pen upon the leaf. 
The rate of travel of those individuals of species which do, move slowly 
up to the adult stage may be determined in the same way. 
All earth used in the insectary should be sterilized and sifted. This 
is necessary in order to destroy disease germs, in order to subsequently, 
regulate the amount of moisture, and in order to destroy predaceous 
mites and also other insects which might be causes of danger or of con- 
