BOMBYCXBbE. 
485 
Boro Polo, Bara Pat. Bombyx textor, Hutt Univoltine. 
Sina, Cheena, Chota Pat. ,, sinensis , Hutt. Multivoltine. 
One important difference induced by domestication is the variation 
in the number of broods ; this is a matter depending largely upon climate, 
the one-brooded (univoltine) being probably the normal habit in a cold 
climate with short summer, the multivoltine found in warm moist loca¬ 
lities. There is a vast literature upon this subject and every aspect of 
this insect and its attendant industry has been fully discussed elsewhere 
(see below, page 489). ‘ Silkworm gut 5 is the fibre used by anglers for 
attaching their hooks, which must be strong and resistant to water ; it 
is the dried silk of the silkworm extracted by dissection from the silk- 
glands of the caterpillars just before it commences to spin, and drawn 
out into a thread from one to three feet long. It consists of the same 
material as silk, only drawn into a short thick thread instead of into the 
extremely fine long thread of silk formed by the insect. It is an article of 
commerce produced in Italy and Japan. 
Silkworms also yield an oil (derived from the chrysalides) which 
is extracted from the stifled chrysalides after reeling. It appears to have 
little commercial value. 
SILK. 
The silk of commerce is the thread employed by certain species of 
insects of the families Saturniidce and Bombycidce (and in Mauritius a 
Lasiocampid) for the formation of their cocoons. There is an immense 
literature on the silk insects of India and we are not concerned here with 
the commercial aspect of this question (See Watt’s Dictionary of 
Economic Products, Vol. VI, Pt. III). Using the term in the wider sense 
to denote the thread produced by insects for cocoon-making or other 
purposes, we find that the faculty of silk-production is not confined to 
the few economically important species but is general among a very 
large section of the insect world. 
As a rule, silk is formed in the body of the insect as a fluid in the 
salivary glands which open by two minute apertures on the apex of the 
lower lip ; the salivary glands are long sac-like structures with walls 
composed of large cells, and ending in two fine ducts which lead to the 
lower lip. Silk is poured out as a thick gummy fluid usually transparent, 
which rapidly hardens and dries, assuming then a tint of buff, yellow 
or brown. When used in cocoon-making, the insect spins a continuous 
thread at first on the object to which the cocoon is fixed, later building 
up the cocoon of continually added threads. The outer layer is somewhat 
irregular and not necessarily continuous, as it has to be adapted to the 
