Jan. 1, 1904.] - l^HE TROPICAL 
At present the cotton worm parasites are very few 
in proportion to the extreme abundancj of the host, 
but later the proportion of parasites to host will be 
much higher. 
Insects in their native localities and under normal 
conditions are less likely to become epidemic, than if 
they are introduced to new localities or if the condi- 
tions become considerably changed. This is beoanae 
the relation of host to parasite is upset, the parasites 
having to accustom themselves to the new host, or 
the host having opportunities for rapid development 
which enable it to increase to a remarkable extent in 
spite of its parasites. 
Extreme abundance of any insect pest is usually 
followed by a season of comparative scarcity, which is 
due to the development and increase in number of the 
parasites consequent upon the extreme abundance of 
its host or food supply. Later, other parasites may be 
bred from the eggs or the adult, and experiments|will be 
tried by this Department as to ways for increasing the 
numbers of the parasites already knov/a,— Agricultural 
News. 
* 
INDIA-RUBBER LATEX. 
THE ERESENCK OF INDIA-RUBBER AS SUCH IN THE LATEX. 
India-rubber is a product of such extraordinary 
physical properties that already years ago I came 
io entertain strong doubts as to the presence in the 
India-rubber latex of india-rubber as such. It is, of 
course, impossible to decide this question without an 
ample supply of india-rubber latex. Unfortunately, 
this is a product which, if shipped into our latitudes, 
always arrives either in an entirely useless condition, 
or, at any rate, having undergone such alterations 
as to render any conclusions based upon its exami- 
nation in that state of rather questionable value. It 
is well known that, by adding to the fresh milk a 
quantity of strong ammonia, it may reaxh here in 
apparently perfect condition, but whether this addition 
of the ammonia has not produced an alteration of 
the milk, rendering it unfit for the conclusive eluci- 
dation of the above point, is likewise a moot point. 
EXPERIMENTS WITH CASTILLOA LATEX, 
For this reason, the following experiments, carried 
out on the spot with the freshly collected milk of 
Castilloa elastica (Caucho rubber) may be of interest. 
The milk obtainable from the different rubber trees 
varies very much in consistency. That of Castilloa 
elastioa is generally obtained in the condition of a 
creamy mass, scarcely liquid. On diluting it with 
water and shaking the mixture, we do not obtain a 
homogeneous milky fluid. The liquid obtained always 
contains a large number of very smsU nodular aggre- 
gates of about the size of a pinhead. The microscopical 
examination of such a diluted milk shows that this 
is due to the fact that the globules occurring in Castilloa 
milk are not single globules, but unite to form 
strings, or clusters of globules, which are not easily 
broken up into their integral parts. Considering the 
Doagalating action of heat upon most kinds of rubber 
milk, it must appear very surprising' that a milk so 
rich in albuminous matter as that of Castilloa elastica 
can be boiled without coagulation, although it should 
be stated that this can only be done with the fresh 
milk. Castilloa milk which has been standing for any 
length of time cannot be boiled without coagulating. 
Even more surprising is the circumstance that, in 
boiling the rather lumpy liquid we obtain on dilut- 
ing this milk with water, all the little lumps and 
knots disappear, and we obtain in this way a perfectly 
thin aud homogeneoua milk which, under the miscros- 
cope, shows itself to consist of enormous masses of 
individual globules. All the globular aggregates before 
mentioned have therefore been brokeu up in the 
(joiliDg. 
AGRICULTUEIST. 495 
THE COLOUR OF CASTILLOA BUBBER. 
On standing, the latex of Castilloa elastica rapidly 
darkens in colour, and is, after a few hours, converted 
into a most uninviting-looking blackish-brown mass. 
This strikiii? change always takes place under the 
conditions under which the natives collect the latex 
aud prepare the rubber from it, and it is chiefly 
responsible for the abominable colour of all the brands 
of Castilloa rubber at ptesent in the market. But 
it must not be understood that thid change of colour 
of the latex involves a change in the india-rubber 
contained in it. If we effect a complete separation of 
the rubber substance of the latex from the aqueous 
vehicle in which this substince is emulsified, we 
find at once that the rubbei remains practically per- 
manently colourless, but that the acqueous vehicle 
undergoes very rapidly the above described discolor- 
ation, and it is therefore evident that in order to 
obtain Castilloa rubber of a light colour, the separation 
of the rubber substance from the aqueous vehicle must 
be effected at the rate at which the latex is gathered. 
Latex discoloured in [the above-described manner, on 
boiling, rapidly coaguLites ; wherea.* the fresh latex, 
as I .have ^already pointed out, cannot be coagulated 
by heat. 
THE PRESENCE OF TANNIC ACID IN THE LATEX. 
In the literature on india-rubber we very frequently 
meet with the statement that rubber latex contains 
tannic acid. Considering, however, that the latex 
contains a very large proportion of albumen which 
is readily and completely precipitated (coagulated) 
by tannic acid, the above statement is obviously wrong. 
If any proof beyond the one just adduced were 
needed, it will be found in the fact that on adding to 
india-rubber latex a solution of tannic acid, complete 
coagulation at once supervenes. I believe that the 
above erroneous statement is 'iue to the incorrect 
interpretation of the fact that Castilloa latex, on 
addition of any salts of iron, assumes a very strong, 
dark green coloration, a reaction characteristic or 
members of the tannin cl .ss. But I found, on closes 
investigation of this point, that in the case of the 
Castilloa latex, this very striking colour reaction if 
not due to the presence of tannin, but to a substance 
belonging to a class of bodies known as glucosides. 
The Igluooside in the Castilloa latex appears to 
be a compound of a crystal lisable sugar fdambonite), 
and a substance closely related to aesouletin, which 
occurs in the horse chestnut. 
REACTIONS OP CASTILLOA LATEX. 
The general reactions of the latex of Castilloa elastica 
are as follows : — 
Ethyl and Methyl Alcohol :— Immediate complete 
coagulation. 
Acetone : — Fairly rapid coagulation, 
Formaldehyde: — No coagulation. Does not coagu- 
late on boiling. 
Formic Acid;— Traces produce immediate coagu- 
lation, which does not take place when the acjd ia 
added in excess. 
Acetic Acid ; — Same as formic acid, acta more 
energetically. 
Inorganic Acids : — Same as acetic acid, 
Ammonia :— In very small quantity produces intense 
greenish-yellow coloration and coagulation ; the latter 
fails when excess of ammonia is used. 
Caustic Soda : — Same as ammonia, more intense 
coloration. 
Ferric Chloride :— Very intense dark green color, 
ation and coagulation. 
Tannic Acid: — Immediate precipitation. 
Hydko-ferro-cy-anic Acjd :— Immediate coagulation. 
Ail the numerous well-known precipitants of the 
alkaloids, including albumen, have the same action 
upon the latex as the two last-named of the above 
re-agents, and thero remains therefore no doubt 
whatever that it is, indeed, not the rubber of the 
latex which is coagulable, but the albumen contained 
in it. ^ 
