48 
The dry-heat method occupies a much longer time. The cocoons are 
placed in shallow baskets and slipped on iron drawers into an oven 
which is kept heated to a temperature of about 200° F. This should 
not be increased for fear of burning the silk. This operation lasts from 
two to twenty-four hours. A certain humming noise continues so long 
as there is any life, and its cessation is an indication that the chrysa- 
lides are ali dead. Where the choking is well done there is little loss, 
only about 1 per ceut. of the cocoons bursting at the ends. After 
choking in this manner, the cocoons should be strewn upon long 
wooden shelves in the shade, with plenty of air, and, for the first few 
days, frequently stirred. After remaining on these shelves for about 
two months, with occasional stirring, the chrysalides become quite dry, 
and the cocoons will preserve indefinitely. They are, however, still 
subject to the attacks of rats and mice, and the little beetles known as 
‘museum pests,” belonging to the genera Dermestes and Anthrenus, are 
attracted by the dead chrysalis within and will penetrate the cocoon, 
injuring it for reeling purposes. In the warm Southern States the 
dry-heat choking can be accomplished by simple exposure to the sun. 
Two or three days of such exposure are sufficient. But, as strong wind 
may annihilate the effect of the sun’s warmth, it is good to have for that 
purpose long boxes, 4 feet wide, sides 6 inches high, to be covered with 
glass frames. This will increase the heat, and, by absorbing the air of 
the box, stifle the chrysalis most surely. The glass cover should be 
slightly raised to permit the escape of the excessive moisture which 
evaporates from the cocoons, and care should be had to keep out the 
ants. 
