92 
Journal of Agricultural Research 
Vol. VII, No. 3 
becomes paresized, and the tongue can no longer be extended. Subse¬ 
quently the mandibles and antennae are stricken. 
Third stage. —At the beginning of this stage the bees are apparently 
dead, except that an occasional twitching of a tarsus or a slight movement 
of the end of an antenna or of the abdomen may be seen. Sometimes an 
abdomen passes through a series of convulsions, and occasionally a small 
amount of feces is voided; in one instance a small amount of liquid was 
seen issuing from the mouth. 
If the behavior of bees dying of nicotine poisoning is interpreted in 
the same way as is interpreted the behavior of higher animals likewise 
poisoned, it seems that nicotine as a stomach poison really kills bees 
by motor paralysis, and that the paralysis travels along the ventral 
nerve cord from the abdomen to the head, first affecting the abdominal 
and thoracic ganglia, then the subesophageal ganglion, and last the 
.brain. Considerable light is thrown on this point in the portion of this 
paper dealing with the tracing of the nicotine from the time it is applied 
to the time it reaches the nervous system. Having decided that nicotine 
kills insects by paralysis, we shall now consider the effects of nicotine as 
an insecticide when applied in practical work. 
2.—NICOTINE SPRAY SOLUTIONS 
The following results are not meant to test the efficiency of any of the 
commercial nicotine spray materials, or of even various dilutions of them, 
but merely to determine how nicotine affects insects when it is applied 
as in practice. 
(a) APHIDS DIPPED INTO SOLUTION OP PURE NICOTINE 
Carolina poplar leaves bearing many aphids {Aphis populifoliae Davis) 
were dipped into a solution of pure nicotine (i: ioo). At once the aphids 
began to exhibit an abnormal behavior and soon showed signs of dying. 
Half an hour later all of them were dead. 
( b) APHIDS SPRAYED WITH SOLUTION OP PURE NICOTINE 
Many more aphids on Carolina poplar leaves were sprayed heavily 
with the above solution. Half an hour later nearly all the aphids were 
dead, every one being dead 15 minutes still later. Before being sprayed, 
these aphids were quiet and seldom moved from place to place on the 
leaves. They usually stood on the first two pairs of legs, with the hind 
pair of legs and abdomen high in the air and with the beaks stuck into 
the leaves. Occasionally an aphid elevated its abdomen higher into the 
air and simultaneously moved its body sidewise in a jerky manner. 
The legs and antennae were moved little, and no liquid was seen issuing 
from the cornicles or from the anal openings. Immediately after being 
sprayedj these same aphids lay flat on the leaves, apparently dead. 
