ARSENICALS. 27 
(mostly Melanoplus femur-rubrum De G.), Delonging to Orthoptera; 
and honeybees {Apis mellifica L.), belonging to Hymenoptera. An 
atomizer was used in all the spraying experiments. 
Silkworms. — Silkworm larvae were fed leaves treated as follows: 
Mulberry leaves were sprayed with the various mixtures, the con- 
trol leaves being sprayed with tap water only. After having been 
dried in the air the leaves were cut into small strips which were then 
placed in small wire-screen cages. An effort was made to put ap- 
proximately the same quantity of food in each cage, so that a rough 
comparative estimate of that consumed could be made. In 1919 
about 50 normal silkworms in the second instar (varying in length 
from 7 to 12 millimeters, with an average of 10 millimeters, and not 
ready to molt) were put in each cage, but in 1920 silkworms in the 
third instar (18 to 30 millimeters long, average 25 millimeters) were 
employed. Counts were made daily except on Sundays, the cages 
being cleaned and treated food being renewed at the same time. No 
disease was noticed among these larvae. 
Webworms. — The webs were collected in the fields from a variety of 
plants on Monday. At the laboratory these webs containing web- 
worms were kept in large cages with a small amount of food until 
Tuesday noon, when the larvse, which were then very hungry, were 
well mixed according to size (all instars but first one). Tuesday 
morning approximately the same quantity of mulberry foliage was 
placed in each of several wide-mouthed bottles containing water. 
It was then sprayed, and, when dry, a bottle with contents was placed 
in a large battery j ar, 8 inches in diameter by 12 inches high. Tuesday 
afternoon approximately the same number of webworms were placed 
in each jar, and thereafter the sprayed food was renewed daily. 
Thus by starting each set of experiments on the same day of the week, 
the days (Sundays) on which no records were taken always fell on 
the fifth, twelfth, and nineteenth days of the tests. Very little 
disease or parasitism was noticed among these larvae. 
Tent caterpillars. — The tents, collected in the fields on wild cherry 
trees, were handled in the same manner as the webs of webworms. 
Sprayed wild cherry foliage was placed in the jars daily and counts 
were made daily. Owing to the prevalence of the " wilt," or polyhe- 
dral disease, it was necessary to test these larvae while in the earliest 
instars. 
Potato-beetle larvse. — Collected on potato plants, these larvae were 
placed in cheesecloth cages, 9 inches square by 12 inches high. They 
were so well mixed before being placed in the cages that each cage 
contained about the same number in the various instars. Sprayed 
potato-plant foliage was given to them daily. Parasitism was com- 
mon only in the last instar. 
Grasshoppers. — The fourth, fifth, and sixth (adults) instars caught 
in the fields were tested in the cheesecloth cages. Having been 
unable to use the foregoing spray mixtures, bran mash, mixed with 
some of the same powdered arsenicals, served as food. Using Paris 
green (sample 64, containing 55.09 per cent As 2 3 ) as a standard, 
and the regular formula 8 as a basis, a modified formula was derived, 
whereby a pint of poisoned bran mash containing each arsenical to 
8 Bran, 25 pounds; Paris green, 1 pound; lemons or oranges, 6; molasses, 2 quarts; and water, from 
2 to 4 gallons. 
