SPECIAL STUDIES FROM THE KING INSTITUTE OF
PREVENTIVE MEDICINE.
VOLUME I.
1907.
No. I.
REPORT ON THE COMPARATIVE VALUE OF PESTERINE AND OTHER
FLEA DESTROYING SUBSTANCES.
By Captain S. R. CHRISTOPHERS, M.B., I.M.S.
In deciding upon the best contact poison for general use against floas it is necessary to
bear in mind that disinfectants or poisons have not necessarily any particular effect in destroy-
ing insects, as they are protected against watery solutions of metallic salts such as perchloride
of mercury and many other active chemicals by their impervious chitinous coats. But there are
substances, on the other hand, notably certain volatile and oily substances, such as xylol, benzine,
napthah, petrol and kerosine which without being disinfectants or even active poisons in the
o r d i n a r y s e n s e h a v e a p e c u l i a r l y f a t a l a c t i o n o n i n s e c t s . T h e m o s t e a s i l y o b t a i n e d s u b s t a n c e o f
this kind is ordinary kerosine which has been used as a rule whenever insect destruction on. a.
large scale has been attempted. Of other cheap substances certain phenyls seem to be active
insect destroyers, Hossack having found these effective under the conditions of his experiments
in dilutions as low as 1 in 800 ; Saigol also gets good results with petrol in phenyl. But as will
be shown later the immersion tests of these authors are very severe and equally high figures are
given by common kerosine diluted in the form of emulsion. On the whole it is very doubtful,
whether on the basis of costliness, which must mainly determine the choice of a substance for
general use there is anything more potent than kerosine in some form or another.
In the destruction of ticks in South Africa and elsewhere kerosine is used in the form of
a spray consisting of about one part of oil to four parts of water thrown by means of oil water spray
pumps and its use is said. to be effective beyond. all other remedies tried. Judging from what
one knows of the action of kerosine on insects it is almost certain that similar spraying would
be effective against fleas. But as will be shown later there is a still cheaper and. equally
e f f e c t i v e w a y o f u s i n g k e r o s i n e w h i c h h a s t h e a d v a n t a g e t h a t s p e c i a l s p r a y p u m p s a r e n o t r e q u i r e d a n d
that pure oil is not placed in the hands of coolies and others likely to misappropriate it.
With a view to reduce cost it has been recommended that the crude oil which is extremely
cheap be used against insects and it is even claimed that crude oil is a still more active
insec—
ticide than the refined oil. But this I very much doubt, the cheap yellow kerosine oil costing
about one rupee eight annas a tin being in my opinion more active than the crude oil, especially
when the two are contrasted as emulsions in different dilutions.
Pesterine
appears to be some form of crude oil. It is a fluid resembling thin coal tar quite
incapable of admixture with water and fouling all with which it comes in contact. Though
cheap its application is really an expensive method of flea destruction since it is used undiluted.
Its unpleasant character alone is sufficient in my opinion to condemn the use of Pesterine or
any form of crude oil as a substance for general use in the disinfection of houses.
By the use of soap solution Pesterine can be converted into a fluid perfectly mixable with
water in any proportion ; and in this form it is very effective against fleas. But even in 1 in
10 dilution the emulsions is very dirty and is in many ways less satisfactory than the emulsions
of refined oil discussed later. It was also not found possible to make a " saturated " emulsion
of Pesterine that mixed well with water and the cost of soap required to make the " unsaturated "
emulsion used in the experiments given later brings up the price of effective solution to that of
refined oil emulsion.
An emulsion of crude oil known as " Crude Oil Emulsion " is recommended by the Govern-
ment Entomologist in a pamphlet on flea destruction and is procurable at the rate of
Rs. 6-14-0 for a five-gallon drum exclusive of carriage. A sample of this substance was
obtained and its effectiveness against fleas tried. It is a jelly somewhat resembling soft soap