44 
given for the determination of the sex of the inclosed insect, and among 
them, perhaps the most common, is the assertion that those that are con- 
stricted in the middle (Fig. 2) contain males, while those not constricted 
(Fig. 3) contain females. This, however, may be regarded as an indi- 
cation rather than a fixed rule, and there are races in which the cocoon 
is almost uniformly constricted and others where the reverse is true. 
But this careful selection for sex is comparatively unimportant, and we 
consider it wiser to choose the cocoons in relation to their firmness and 
texture, and trust to chance to bring as many male moths as female. 
Double cocoons, where two worms have spun together, should never be 
used in egg-making. 
The proper cocoons having thus been selected, they should be strung 
upon stout threads about 3 feet long. Care should be taken not to 
prick the chrysalides with the needle while passing it through the end 
of the cocoon in making the chains. These chains should then be hung 
in a cool, darkened room while waiting for the moths to emerge. They 
should not be placed near any object which would be soiled by the se- 
cretions emitted by the moths on their emergence from their cocoons. 
Previous to this emergence there should be prepared for each ounce 
of eggs to be produced about one hundred small bags of fine muslin 
(cheese cloth makes a good material), made in the following manner: 
Cut the cloth in pieces 3 by 6 inches, then fold one end over so as to 
leave a single edge of about three-quarters of an inch, as shown in Fig. 
Fic. 25.—Cell used in the Pasteur system of egg-laying (after Roman). 
25. This should be sewn up into a bag with the upper end open, and 
then turned inside out so that the seams will cause the sides to bulge. 
Thus completed they are called “cells.” The cells should be strung 
