Oct. 16, 1916 
Effects of Nicotine as an Insecticide 
103 
glacial acetic acid. After remaining in this mixture for about three 
hours, they were placed into absolute alcohol for another hour. 
Phosphotnolybdic acid is one of the alkaloidal reagents, and it pre¬ 
cipitates nicotine even in a dilution of 1 to 40,000. It was prepared 
according to the directions of Autenrieth (1) with modifications as follows: 
A sodium-carbonate solution was saturated with pure molybdic acid;, 
one part of crystallized disodium phosphate (Na 2 HP 0 4 —i2H 3 0) to five 
parts of the acid was added and the mixture evaporated to dryness. The 
residue was fused and the*cold melt was dissolved with absolute alcohol. 
This mixture was filtered and enough nitric adid added to produce a 
golden-yellow color. The resulting mixture, called “ phosphomolybdic 
acid,” was used full strength when mixed with absolute alcohol to serve 
both as a fixative and as a precipitant. The precipitate resulting from 
the union of this mixture and nicotine is neither soluble in water nor in 
any of the alcohols; but for fear of losing some of the precipitate the 
sections were stained in safranin dissolved in 95 per cent alcohol. 
A study of the sections of the coccids treated as described above 
showed a brownish yellow precipitate inside many of the tracheae 
(PI. 1, fig. E, pr)j but it was not seen elsewhere inside the integument. 
In the sections of coccids used as controls no precipitate was seen any¬ 
where. It is thus seen that nicotine solutions containing no stains are 
able to pass into the tracheae of coccids that have been submerged in 
the solution for 30 minutes. 
(b) Jt BILITY OP NICOTINE} SPRAY SOLUTIONS TO ENTEJR SPIRACLES 
Aphids {Aphis hrassicae , A . rumicis L., and Macrosiphum sanborni Gill.), 
and coccids (Orthezia insignis) were sprayed with a pure nicotine solution 
(1:500), colored with carmine acid, until they were wet with spray. 
An hour later they were mounted on slides, as described on page 100, 
and were examined. The spray had evaporated, leaving the red stain 
adhering to various parts of the integuments. Nearly all of the tracheae 
showed no signs of the stain; but a few seemed to be slightly pink, 
although this kind of an examination is not entirely reliable. 
The preceding experiments were repeated by heavily spraying aphids 
{Aphis rumicis) with a pure nicotine solution (1:500), colored with 
indigo-carmine. The sections were stained as described on page 101. 
A thorough study of these slides showed that the colored nicotine solu¬ 
tion had not passed through the integuments nor into the tracheae. At 
only one place was it found that the “precipitate” had lodged in a 
spiracle (PI. 1, fig. 6, sp); but it was-never observed in the tracheae 
(PI. 1, fig. 7, tr), nor elsewhere inside the integuments, although it was 
commonly seen adhering to the outer surfaces of the integuments (PI. 1, 
fig. 7, inf). 
Aphids of the same species as just described were heavily sprayed 
with a pure nicotine solution (1:100), not colored with any stain. These 
