228 Annals Entomological Society of America |Vol. XIV, 
plant food used was that known to plant physiologists as 
Pfeffer’s solution and is prepared as follows: 
Calciuminitrateveent sca: ok ccc chet ee 4 grams 
Potassiumyenitrahesnaanac wince. sere cre eee 1 gram 
Macnesiumusul phate s..y0- son soheeec ao noraner tae & 
Potassium dihydrogen phosphate................ i 
Rotassiumuchilonides: a4 5:2 heres er eepaereentera e O57 
Hern crehloridens), ot, s siti Pee ee en ee ae Trace 
Dictilledwatere ns iced See ae eee 
The plants grew well in this solution, 
although at times some difficulty was en- 
countered by the growth of alge in the 
liquid. This was largely overcome, however, 
by painting the bottles black. Usually the 
plants lived long enough for experimental 
purposes without changing the liquid. When 
the experiments were prolonged the solution 
was changed as often as necessary. 
By using this method, it was possible 
to follow the life history of the Hessian fly 
from oviposition to the formation of the 
puparium. The plants could be handled 
conveniently and the various stages studied 
with greater ease and exactness than when 
the plants were grown in the soil. When 
necessary, the plants could be removed from 
the bottle and placed under the binocular 
for close study. By carefully shaving the 
epidermis of the leaf sheath, it was possible 
to keep the larve under observation at all 
times. As the larve increased in size they 
could readily be seen through the neck of 
the bottle. 
This method proved so successful in the 
Hessian fly work that it was adopted for 
the study of a number of other insects 
infesting cereal crops. Thus far the writer 
has grown wheat, oats, rye, barley, corn, 
3 to 7 liters* 
tM 1 
FEROS ARS 
ex Sy 
7 aE e 
ea de 
ay | Bek 
My 
i) 
Eres 
Wheat plant growing 
in a nutrient solution. 
C—Cell for confining 
insects on the plant. 
and many of the sorghums in Pfeffer’s solution in connection 
with studies of the chinch bug (Blissus leucopterus Say), green 
* The writer has found that five liters is best for the work under consideration. 
