<xi MONTHLY. 
Vol. XIX. 
COLOMBO, NOVEMBER 1st, 1899. 
No. 5. 
REMEDIAL MEASURES AND 
INSECTICIDES. 
By E. E. Green, Government Entomologist. 
(Continued from page 231.) 
EFORE quitting the subject of 
general remedial measures and 
entering upon detailed descrip- 
tions of particular processes, 
something should be said upon 
the important question of the 
introduction of ' natural ene- 
mies ' oi ihe CoccicVe. The same 
circumstances that make an imported pest eo ex- 
ceptionally dangerous act in our favour in the importa- 
tion of beneficial insects. Just as the absence of its es- 
tablished natural enemies enables an insect pest to 
multiply without hindrance, so the introduction of 
a beneficial insect without its own natural checks 
will also permit of its rapid increase as long as an 
ample supply of congenial food is obtainable. When 
the food supply begins to fail, which means when 
the pest has been mastered by its imported enemies, 
then they will both decline together. There need be 
little fear that, when the food supply has been ex- 
hausted, the imported insect will itself become a pest. 
A predatory insect, by which is understood one that 
preys upon other insects or animals, will seldom, if 
ever, alter its diet and become a vegetarian. 
It is noticeable that an insect seldom assumes 
any importance in its original home, unless through 
some accidental or artificial interference with the 
balance of nature in that part. (For instance, it has 
been asserted that the widespread destruction of 
moles in England has resulted in a marked increase 
of damage to pasture land from the grubs of the 
'cockchafer' beetles and 'crane-flies,' upon which 
the moles fed.J Consequently, if we are to obtain 
any benefit from the use of natural agents, we must 
endeavour to reproduce the conditions prevailing in 
the country where the insect in question is known 
to occur, though without attracting notice as a pest. 
Or, it the original home of the injurious insect is 
unknown, we may reasonably hope for good results 
from the introduction of an insect that is found to 
prey upon some allied pest in another country. 
The most important natural enemies of the scale 
iasects, or, at least, those that have attracted most 
attention, belong to a family of small beetles popu- 
larly known as lady-birds,' The complete success 
attending the introduction of an Australian lady bird 
(Vedalia cardimJis) into California, where it cleared 
the orange orchards of the destructive ' Fluted-scale' 
(Tcenja jmrchasi) has led to numerous other experi- 
ments of a similar kind. These experiments have 
not always been successful. There must, of necessity, 
be many failures. We are still only in the experi- 
mental stage of the work. Even when the bereficial 
insects has been successfully established in a country, 
it is by no means certain that it will thrive. There 
may be climatic or other conditions against it. In 
that case, all we can do is to try another insect. 
Occasional, or even repeated, failures should net dis- 
courage the repetition of the attempt. The value of 
a single success will far outweigh the cost of many 
failures. In the course of such expeiiments the canscB 
of failure will in time be ascertained, and improved 
methods be employed. The freezing method recom-' 
mended by Mr. Kcebele seems to be rather an un- 
certaiu one, and has led to many disappointments. 
I am inclined to hope for more satisfactory results 
from the employment of ' Wardian cases,' as suggested 
to me bv Mr. Lounsbury. In these the insects will 
remain active and be supplied with food. There are 
certain obvious dangers connected with this method, 
such as the possible introduction of the insect pest 
upon which the ' lady-birds ' have been supported 
during the voyage. For this reason the business 
should be conducted under the supervision of trained 
entomolongists only. In choosing the food supply, an 
insect that already occurs in the country to which 
the lady-birda are consigned should, if possible, be 
selected.* But, under any circumstances, the im- 
ported beetles should not be liberated immediately, 
but should be transferred to fresh breeding cages 
and supplied with local food, and the cage in which 
* In a recent consignment of 'lady-birds' received 
from the Cape of Good Hope, the cochineal insect 
(Coccus cacti) was very judiciously chosen for the 
purpose. This insect is practically confined to the 
'Prickly Pear' cactus, and is therefore not liable to 
become a pest. 
