SATURNIIDjE. 
481 
that this is purely a matter of climate ; it is impossible to grow any kind 
of silk profitably unless the climate is suitable, which it is only in well 
defined tracts for each species. It must also be remembered that the 
production of a textile fibre from silk caterpillars of whatever kind 
requires primarily an abundant supply of absolutely cheap labour 
in whom the occupation is hereditary; given all other conditions, 
a suitable equable moist climate, a healthy race, a supply of food- 
plant, and a demand for the fibre, silk as an industry cannot be carried 
on except by low-paid people to whom the occupation comes naturally 
from childhood ; it has never and will never be carried on in countries 
where living is dear or where labour finds high wages, unless the 
demand for silk increases ; no insect fibre can be produced at the 
low cost of a vegetable fibre ; the lowest price for a pure silk (£120 a 
ton for eri cocoons) is above the price of all vegetable fibres excepting 
that of the very best flax which reaches this price in some years. 
The attempts to grow silk in the United States for instance have all 
ended in failure for this reason. 
Cricula trifenestrata , Hell, is the only species which can properly 
be brought within the fauna of the plains of India. Its caterpillar lives 
upon the mango tree in lower Bengal and Burma ; it is clothed in 
poisonous spines and therefore dangerous to handle ; Mr. Jamini Mohan 
Ghose informs me that it is a common belief in Mymensingh that if 
the mouth touches any portion of the human body, that part will 
decay as in leprosy ; the caterpillar is accordingly feared and nothing 
is done to check it, though it wholly defoliates the mango tree. 
Attempts to make an industry in it, for spun silk, have been made 
in Burma (Silk in Burma, J. P. Hardiman, p. 20). 
EMERGENCE FROM THE COCOON. 
Very little attention has been paid to that one moment in the lives 
of so many insects when the imago emerges from the pupa and has to 
make its way out of the cocoon or other pupal envelope. If the cocoon 
or covering is sufficiently perfect to resist the weather and the foes of 
the pupa, how is the usually soft and delicate insect to escape ? We 
have not space here to discuss this exhaustively, nor are the data 
available for many Indian insects ; we indicate some of the commonest 
methods chiefly in order to direct the attention of the student to this 
neglected point. 
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