236 
INSECTS USEFUL TO AGRICULTURE. 
INSECTS USEFUL TO AGRICULTURE. 
We condense, principally from a recent work 
of J. H. Fennell, some interesting facts relating 
to this much-neglected class of animated nature. 
Were the habits, economy, and capabilities of 
this large, but unpretending family, fully known, 
mankind would be able, annually, to add mill- 
ions to their products, or save hundreds of 
millions from their ravages ; and we can offer 
no better suggestion to some young students of 
nature, some modern Linneeus, than a thorough 
explanation of the insect history of this broad 
American continent, hitherto almost wholly un- 
known. 
Some of the Chinese silkworms spin white 
silk, but some regard them as only a variety of 
the common species, and not as a distinct one. 
They slightly differ from the common silkworm 
by a blackish spot on each side of the head; 
and the moths, which began to appear at the 
close of August, were perhaps rather larger, 
and the dark lines on the wings were of a little 
deeper color. From the hatching of the egg to 
the death of the moth, this variety's existence 
averaged 100 days. The silk was not so abun- 
dant as on the cocoon of the common sort ; of 
not quite so strong a texture; less easily wound 
off; but as the silk is beautifully soft and per- 
fectly white, further caTeful observation may 
show that it is better adapted to some purposes 
in manufacture than the pale-yellow and orange 
sorts of silk* 
The caterpillars of the Atlas moth, (Attacus 
alias, Germar,) a native of Surinam and other 
parts of America, and also of China and other 
parts of Asia, feed on the leaves of the citrus, 
and spin silken cocoons of great size, which 
sometimes unwind in threads of many ells in 
length, more firm and tenacious than common 
silk, but the cases are very difficult to unravel, 
and are commonly carded. In the East Indies, 
silk is obtained, also, from the cocoons of two 
other species, namely, Attacus mylilta and A. 
cyn£hia.\ In India, three other native species 
are also used; for instance, the Tusseh silk- 
worm, which feeds in the jungle on the jujube 
tree; the Arrindy, which feeds on the Palma 
Chrisli; and the Moongha, whose produce is 
used there to an extent of which we have but 
little idea. 
In South America, there are several caterpil- 
lars, besides those of the common silk moth and 
Atlas moth, which yield excellent silk, Spix 
says that, in Brazil, a species of silkworm is 
abundant on a laurel-like shrub, particularly in 
Maranhao and Para. He says, that although 
its thread promises a much more brilliant silk 
than that of Europe, it has never been employ- 
ed, although it might be with very great facil- 
ity.! At Maranhan and Rio Janeiro, the cater- 
pillars of several species of hombyx spin their 
cocoons of a thicker and stronger silk than that 
of the common silkworm; and Padre Mestre, 
who gave the former a trial, found that it forms 
'Entomological Society's Transactions, 1837, vol. ii. p. 40 . 
\ See Linnaean Transactions, vol. vii., and Colonel Sykes'a ac- 
count of the Kolisura Silkworm of the Deccan, in the Asiatic So- 
ciety's Transactions, 1834, vol. iii. 
t Spix's Brazil (1823—31). 
a very solid material. It has been proposed to 
cultivate for the feeding of them a species of 
mulberry with small inedible fruit, growing 
near Rio Janeiro. 
A caterpillar, which the Indians call sustillo, 
of the tribe and size of the silkworm, feeds on 
the leaves of the pacal, a common tree in Peru, 
and fabricates a kind of silk paper veiy similar 
to that made in China. When the caterpillars 
are about to transform, they assemble at the 
body of the tree, and co-operate in forming, 
with the greatest symmetry and regularity, a 
web of admirable texture, consistency, and lus- 
tre, and which is larger or smaller according to 
their numbers. Beneath this web, they all 
unite ; and, disposing themselves in vertical and 
even files, form in the centre a perfect square. 
This done, each of them spins its cocoon of a 
coarse and short silk, in which it changes to a 
chrysalis. By-and-by the chrysalis becomes a 
moth, which, impatient of further confinement, 
and anxious to take wing, breaks its way though 
the general web, the fragments of which conse- 
quently remain suspended to the trunk of a tree, 
waving to and fro like streamers, and become 
more or less white, according to the situation 
and atmosphere. This natural silk paper has 
been gathered measuring a yard and a half, of 
an elliptical shape, which is peculiar to all of it. 
The caterpillars of the common ermine moth, 
(Yponorneuta padella,) are gregarious, and nat- 
urally construct a very fine close web, impene- 
trable by air, but easily detatched from the 
trees. M. Habenstreet, of Munich, induced them 
to spin it on a suspended paper model, to which 
he gave the form and size he required; and he 
thus obtained square shawls of an ell width, 
others two ells long and one wide, a balloon 
four feet in height and two in horizontal diam- 
eter, and all of a much lighter fabric than the 
finest cambric ; the balloon weighed less than 
five grains, and the flame of a single match held 
under it for a few seconds would raise it to a 
good height, whence it would not descend for 
half an hour ; a shawl of the size of a square 
ell, when stretched and blown into the air, re- 
sesembled a very light smoke passing over ; a 
whole lady's dress, with sleeves, but without a 
seam, he presented to the queen of Bavaria, 
who mounted this fairy-like attire on another 
dress, and so wore it on many great occasions ; 
a shawl of a square ell in size cost only eight 
francs. The caterpillars, two of which are able 
to produce a square inch of this delicate fabric, 
glue their threads closely together while spin- 
ning, and to increase the thickness of the layer, 
if necessary, they were made to pass repeatedly 
over it ; many were of course employed, and 
those parts of the model and patterns not to be 
covered were rubbed with spirits of wine, which 
prevented the caterpillars from working over 
them. A web seven feet square, perfectly pure, 
and as brilliant as taffety, was the result of 
three weeks' labor of about 500 caterpillar.s* 
Latreille" and other naturalists have recom- 
mended a trial of manufacturing articles from 
the silk of the caterpillar of the crimson under- 
*Ls Journal de ^a Societe d'Emulation, &c. 
