BENEFICIAL VERSUS INJURIOUS INSECTS. 
44 per cent. by weight being obtained. Such a process may be distasteful 
tv us, but when the oil is hydrogenated, its uses are greatly extended, 
and its source and nature will remain unrecognised. The blowfly must 
henceforth be included in group 5, in Germany, at least. 
The method of employing one insect to control another was largely 
adopted by Decaux, in Picardy, in France, in 1881. He had observed 
great numbers of tiny flies emerging from the buds of apple trees 
attacked by the Anthonomus weevil (similar to the cotton boll weevil— 
A. grandis). He collected damaged buds, and preserved them in boxes 
covered with gauze. When the paras‘tes hatched out they were ltberated 
in an orchard—over a quarter of a million of parasites being thus set 
free. This was repeated in the following year, and served to free the 
orchard from weevil for about ten years. Berlese, in Italy, extended 
these methods in the fight against Diaspis pentagona, a scale insect, and 
one of the worst enemies of the mulberry in Italy. 
It has been in America, however, that this method of control has 
been adopted to the greatest extent. 
CARNIVOROUS BEETLES AND THEIR PREY. 
1; Carabus nemoralis; 2. Calosoma sycophanta; 3. Carabus auratus; and 4, its larva. . 
About the beginning of this century, the San José Scale and the 
Cotton Boll Weevil threatened two important industries. As a result 
of the entomological investigations in these two problems, many advances 
were made in the methods of insect control, and considerable informa- 
tion gained concerning the relations of injurious insects to other 
organisms and to external factors.* Paris Green had been adopted as 
a standard remedy against Colorado Potato Beetle, and kerosene emul- 
sion had been developed against sucking insects. These remedies were 
followed by hydrocyanic acid gas and lime-sulphur wash, and many 
experiments were made with beneficial insects. In the last decade, 
in the attempts made to solve the problem of the control ‘of the Gipsy 
Moth and Brown Ta‘] Moth, both introductions from Europe, and the 
cause of widespread destruction of forest timber trees, important 
advances have been made towards a better understanding of parasitic 
insects, and of the part they are likely to play in the control of injurious 
475 
