_ REPORT OF THE ENTOMOLOGIST 223. 
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disease is both contagious and infectious, because the corpuscles which 
have been passed with the excrement or with other secretions of dis- 
eased worms have been taken into the alimentary canal of healthy ones 
in devouring the soiled leaves, and because it may be inoculated by 
wounds infiicted by the claws. It is hereditary on the mother’s side, 
because the moth may have the germ of the disease and yet vviposit. 
Indeed, the eggs may be affected and yet look fair and good, the mi- 
croscopic psorospermie not being visible, so that the only true test of 
disease or health is an examination of the parent moth; and by killing 
off all infected moths the disease can be controlled. 
“ Both the diseases mentioned are, therefore, in the strict sense of the 
word, silk-worm plagues; the one of a fungus and the other of an epi- 
zootic nature. Each may become epidemic when the conditions are fa- 
vorable for the undue multiplication of the minute organisms which 
produce them, or when the checks to the increase of such organisms are 
removed by carlessness or ignorance.” Cleanliness and purification are 
absolutely necessary in treating both these diseases, and in pébrine care 
must be taken to see that the eggs are sound by a microscopic examina- 
tion of the moths. This may be done after the eggs are laid, and if the 
corpuscles be found in the mother, her eggs should be discarded. 
Silk-worms are subject to other diseases, but none of them have ever 
acquired the importance of those described. What is called gattine by 
older authors is but a mild phase of pébrine. The worms are apt to be 
purged by unwholesome leaves; too great heat makes them sickly; or 
they may become yellow, limp, and die of a maiady called grasserie or 
jaundice, which is almost sure to appear in large broods, and which is very 
common in those reared in this country. When the worms die from 
being unable to molt they are called luseties, and such cases are most 
abundant at the fourth molt. All these different ailments, and others 
not mentioned, have received names, some local, others more general; 
but none of them warrant further notice here, as they are not likely to 
become very troublesome if proper attention and care be given to the 
worms. 
VARIETIES OR RACES. 
As before stated, domestication has had the effect of producing nu- 
merous varieties of the silk-worm, every different,climate into which it 
has been carried having produced either some changes in the quality of 
the silk, or the shape or color of the cocoons, or. else altered the habits 
of the worm. 
Some varieties produce but one brood in a year, no matter how the eggs 
are manipulated; such are known as Annuals. Others, known as Bivol- 
tins, hatch twice in the course of the year; the first time, as with the An- 
nuals, in April or May, and the second, eight or ten days after the eggs 
. are laid by the first brood. The eggs of the second brood only are 
kept for the next year’s crop, as those of the first brood always either 
hatch or die soon after being laid. The 7revoltins produce three annual 
generations. There are also Quadrivoliins, and, in Bengal, a variety 
known as Dacey, which is said to produce eight generations in the course 
of a year. Some varieties molt but three times instead of four, espe- 
cially in warm countries and with Trevoltins. Experiments, taking into 
consideration the size of the cocoon, quality of silk, time o¢cupied, 
hardiness, quantity of leaves required, etc., have proved the annuals 
to be more profitable than any of the polyvoltins, although Bivoltins 
are often reared; and Mr. Alfred Brewster, of San Gabriel, Cal., says 
that he found a green Japanese variety of these last more hardy than 
