18 BULLETIN 737, U. S. DEPARTMENT OF AGRICULTURE. 
hatched about November 10, 1915, and when partly grown were 
placed in granulated eblane eipatee and kept in a cool room 
did not transform until April, 1916. The material was protected 
from severe freezing, but only a small proportion of the larve sur- 
vived the winter. The most favorable conditions for the rapid 
development of larvee are created by (1) suitable food substances in 
compact or concentrated form, (2) high and uniform temperature, 
(3) high humidity, (4) protection from strong light, and (5) protec- 
tion from rapid evaporation. At Richmond, Va., during the period 
between August 1 and November 19, 1914, the shortest larval period 
observed in six lots of about 20 larvee each was 39 days, and the 
longest period was 61 days. Pressed chewing tobacco was used as 
food. The maximum temperature during the period was 91° F. 
and the minimum temperature was 51° F. At Key West, Fla., 
during the period between April 16 and June 24, 1912, in cigars 
kept at room temperature, the shortest larval period observed was 
42 days and the longest period 66 days. The temperature of the 
room varied from 80° to 94° F. 
Numerous experiments have shown that with concentrated foods 
the larval period is shortened somewhat. In several experiments 
with different foods kept under the same conditions in an automati- 
cally regulated incubator at a constant temperature of 86° F. the 
larval periods were as follows: In tobacco seed, 2 experiments, 29 
and 30 days; in pressed yeast cake, 2 experiments, 27 and-30 days; 
in pressed plug chewing tobacco, 29 days; in sliced plug smoking — 
tobacco, 30 days; in loose granulated tobacco, 2 experiments, 35 and 
38 days; in cigars, 2 experiments, 34 and 36 days; in cigarettes, 
42 days. 
At Clarksville, Tenn., the following records for the larva stage 
were obtained at room temperatures during summer: 
TABLE I1.—Length of larva stage of the tobacco beetle (Lasioderma serricorne), 
Clarksville, Tenn., 1914. 
| 
Larva 
Egg Larva | Daysas - 
Beco No. hatched— ouuee pupated—| larva. Hoots 
Re oR SEES 5 Sas a eee Mec Rent June 7-.-| July 18...) July 22- - 45 | Pressed plug tobacco. 
DE eo 8 PEE Sc Bos So te eae dose. 2s As. 52s eAiee sli 71 Do. 
Se ea ee ae are ee et Mh ee GOSS AMIE sa Ades ales 65 Do. 
ARPES AEP RIVA SS EE Sy eae aw do....| Aug.11--..) Aug. 16. 70 Do. 
NASR anes ae ek eee eee ee June 19.-} July 16....| Aug. 20 - 31 | Tobacco seed. 
DSaecnesee meee ee ne Chea, See June 25..| July 30.-..| Aug. 2- - 38 Do. 
Teen EM EM CSM LEI YS FON June 30..| No record .| July 25. - 25 Do. 
THE PUPAL CELLS. 
After the larva has become fully grown and is ready to transform 
into the pupa stage it forms, in any convenient place, the cell or 
cocoon in which transformation takes place. Apparently no special 
