THE LESSER GRAIN-BORER. 43 
of 1J pounds to 1,000 cubic feet of air space. Exposure was for 48 
hours, at the end of which time, when the box was opened, no odor 
whatever remained of the bisulphid, showing that the exposure had 
been complete. The box was made approximately air-tight, but 
seemingly not so tight as was supposed, by pasting over the apertures 
of the cover with paper. The result was a failure. Rhizopertha 
dominica was apparently unharmed. As there were many dead 
beetles present with the living individuals in the rice, the precise per- 
centage could not be accurately determined.** Average temperature, 
about 65° F. 
Experiment No. 19. — The failure of the first experiment with 
bisulphid of carbon at the rate of 1J pounds to 1,000 cubic feet of 
air space — which was not unexpected — led to the doubling of the 
strength (3 pounds to 1,000 cubic feet) for the next series of 
experiments. 
In this experiment, started January 7 at 4.30 p. m., the tempera- 
ture was 68° F., with a minimum of 46° and an average of about 
62° for an exposure of 40 hours. 
When examined 24 hours after the end of the exposure the insects 
were all dead. & 
Experiment No. 20. — Conditions the same as for Experiment No. 
5 and a duplicate fumigating box. Starting temperatures 55° F., 
and at the end of 24 hours 58° ; average 56°. 
Twenty-four hours after the insects were removed from the fumi- 
gator and thoroughly aired, many living specimens could be found, 
showing the experiment to be imperfect. The beetles of Rhizopertha 
dominica were mostly dead, but a very few were alive, although not 
very active. 
Experiment No. 21. — The fourth experiment was conducted in a 
special air-tight fumigating box. the temperature being 45° at the 
start and 42° at the end of 40 hours. There was, however, a mini- 
mum of 36°, and the average temperature was estimated at 42° F. 
a In another bag, in which were specimens of the Indian-meal moth {Plodia 
interpunctella Hiibn.) and Silvanus surinamensis L., the larvae of the former 
and the beetles of the latter were not affected, so far as could be observed, 24 
hours after having been removed from the fumigating box. A week later the 
meal-moth larvae were found entirely unaffected. Tribolium navale Fab., both 
beetles and larvae, survived, as did also the larvae of Tenebroides mauritanicus L. 
6 Other insects were also exposed, including the adult of Tenebroides mauri- 
tanicus L., and great numbers of the rice weevil (Calandra oryza L.) in wheat. 
c The few individuals of Silvanus that were on the outside of the dried figs 
in which they were working were killed, but those which were protected in the 
interior were apparently unharmed. The same was true of Plodia, all of which 
were unharmed. Adults of Tenebroides mauritanicus were unaffected. Some 
Calandras were the same, and probably no strong individuals were killed. 
