ILLUSTRATIONS 
PLATES 
Effects of Nicotine as an Insecticide 
Plate i. A.— Portion of the large longitudinal trachea of the house fly cut 
crosswise obliquely, showing the carmine acid “ precipitate. ” B.—Combi¬ 
nation drawing from two consecutive sections of a green peach aphis, show¬ 
ing the indigo-carmine “ precipitate. ’ * C.—Cross section of a large longitu¬ 
dinal trachea of larva of lesser wax moth, showing the indigo-carmine 
“ precipitate ** adhering to the tracheal wall. D.—Longitudinal section of 
one of the smallest tracheae of the same larva as in figure C. E.—Longitu¬ 
dinal section of a large trachea and one of its branches of a coccid, showing 
the “ precipitate ” resulting from the union of pure nicotine and phospho- 
molybdic acid. E.—Portion of a cross section of an aphid, showing the 
indigo-carmine “precipitate ’’ in a spiracle. G.—Portion of a cross section 
of the same aphid as in figure F, showing no precipitate in the trachea but 
much on the outside of the integument. H-O. —Longitudinal sections of 
spiracles with connecting tracheae, showing how it is practically impos¬ 
sible for aqueous spray solutions to enter spiracles, owing to hairs, a closing 
plate, and a peculiar arrangement of rims at mouths of spiracles. H. —Spi¬ 
racle of a coccid. I.—Spiracle of a caterpillar of A tteva aurea. J.—Spiracle 
of a larva of lesser wax moth. K.—Spiracle of a caterpillar of Datana sp. 
L.—Spiracle of a caterpillar of a catalpa sphinx. M.—Spiracle of a larva of a 
Colorado potato beetle. N.—Spiracle of fall webworm. O.—Spiracle of 
the tomato worm, showing the closing plate. 
Plate 2. A to J. —Cross sections of portions of the alimentary canals and Mal¬ 
pighian tubules of worker honeybees, showing “precipitated’' indigo- 
* carmine that had been fed with pure nicotine and honey to bees three days 
before they were fixed in absolute alcohol. A. —Portion of the wall of the 
ventriculus, showing the “ precipitate ’' in inner ends of the epithelial cells. 
B. —Portion of the wall of the ventriculus, showing the “precipitate” in 
the middle of the epithelial cells. C.—Portion of the wall of the ventricu¬ 
lus, showing the “ precipitate ” in the outer ends of the epithelial cells and in 
the transverse muscle layer. D.—Portion of the wall of the honey stomach 
joining the pro ventriculus, showing the “ precipitate ” in the chitinous and 
muscular layers. E.—Portion of the wall of the anterior part of the valve 
of the pro ventriculus, showing the “precipitate” in muscles, tracheae, and 
epithelial cells. F.—Section through the small intestine, showing the 
“precipitate” in the center of the lumen and lining epithelium, but none 
in the walls of this organ nor in the Malpighian tubules by it. G.—Section 
through two Malpighian tubules against the ventriculus, showing the 
“precipitate” in their cells and lumens. H. —Section through two Mal¬ 
pighian tubules near the ventriculus, tracheal branch and blood, showing 
the “precipitate” in these tissues. I.—Section of one-third of the 
rectum in a compressed condition, showing the “precipitate” in the 
lumen, but none in the chitinous layer, rectal glands, or muscular layer. 
J. —Section through the middle of the ventriculus, showing the dis¬ 
tribution of the “ precipitate ” in the lumen, between the peritrophic mem¬ 
branes, in the epithelial and muscular layers of the ventriculus and in the 
Malpighian tubules. 
(vn) 
Page 
122 
122 
