PART 1IV. 
difficulty. As an example of what can be done by legislation to 
increase the numbers of an insectivorous bird, and at the same time 
as a still better example of what should not be done in the way of 
indiscriminate protection, may be cited the case of the Buff-backed 
Egret (Ardea Ibis) in Egypt (6)+ 
This bird was abundant twenty-five years ago, but by 1912, owiny 
to its having been killed off by plume hunters, only two small colonies 
of a few pairs each remained. A law was then passed for its complete 
protection; by 1920 there were at least 100,000 in the country, and 
by 1924 perhaps nearly a quarter of a million. By this time the bird 
had become a serious nuisance in several ways, and doubts were 
entertained whether it was really as beneficial as had Leen stated in 
destroying the Cotton worm (Prodenia litura) and other pests. An 
investigation was therefore undertaken, and the stomachs of numerous 
birds examined at short intervals over a period of a year. Not one 
single cotton worm was found in any of the stomachs; the only pest 
of importance on which the bird fed in quantity was the cutworm 
(Euzoa ypsilon), while even the good it thus did was probably 
rendered nugatory by the fact that it also devoured in numbers the 
most useful parasite of the cutworm, as well as other beneficial 
animals and insects. 
The utilisation of the smaller forms of life—insects, protozoa, 
fungi and bacteria, which may be enemies of an insect pest, naturally 
presents more difficulties, and cannot be effected simply by the 
passing of a law. The most obvious method is the introduction of a 
beneficial organism from a foreign country; and while there have been 
notable examples of success, as for instance the introduction of the 
lady-bird Novius cardinalis into California to control the Fluted Seale 
of Citrus (Icerya purchasi), the greater number of attempts turn out 
to be failures. This may be due to unfavourable climatic conditions 
in the new country, but perhaps more often the failure is due to some 
less obvious cause which cannot be ascertained until the experiment 
has been made. Thus the lady-bird known as the Mealy-bug 
Destroyer (Cryptolemus montrouzieri) has been introduced from 
Australia into numerous countries, among which may be mentioned 
the United States, Egypt, and Kenya. In none of these countries 
has it been able to maintain itself naturally, though in all three it 
thrived and bred abundantly in the Laboratory. In America, except 
in a few small areas, the adverse condition appears to be climatic 
(8, p. 114)1, the winters being too cold for the mealy-bugs to breed, but 
not cold enough to force Cryptolemus to hibernate: consequently the 
lady-bird dies out during the cold weather from scarcity of food. 
The practice in those parts of America is therefore to breed enormous 
quantities of this lady-bird artificially, and to liberate them each year, 
a practice which is only economically possible on a very large scale, 
and in a country where plenty of skilled labour is obtainable. In this 
country and in Egypt, although the climate is favourable, Cryptolemus 
never appeared to survive after liberation for more than a very short 
period. In both cases this was due to their being attacked by ants 
attending the mealy-bugs; consequently the system of yearly liberation 
as practised successfully in parts of America, would be useless in 
either of these two countries (even were it practicable on the score of 
expense and available labour) unless something were also done to 
control the ants. 
' See list of references on page 194. 
187