84 
Applied Entomology 
important practical results which might be applied, in many instances, 
at no great cost of labour or outlay of money. 
The importance of another series of tropisms, namely phototropism, 
has also been recently emphasised by Dewitz (1912, p. 343). He men¬ 
tions that the reaction of insects to various luminants was first made 
use of practically by the Abbe Roberjot in 1787. The Abbe en¬ 
deavoured to destroy the vine moth {Oenopthira pilleriana) by means 
of lighted candles placed in the windows of his house, and by wood fires 
in the vineyards. Since that time, this method has been extensively 
developed in France, and in the vineyards of Champagne an elaborate 
installation of electric lights is used for trapping and destroying insects 
destructive to the vine. Much ingenuity has been expended in 
devising light traps, but the fundamental scientific aspect has been 
neglected. It is important to ascertain the optimum candle power 
desirable, and which portion of the spectrum exercises the most marked 
attraction to insects. It is further desirable to make a spectroscopic 
examination of the various kinds of lights likely to be used, and whether 
the reactiotis of various insects differ in a marked degree from one 
another. Perraud (1904, p. 619), so far, is the only investigator who 
has paid much attention to this side of the subject. Projecting a large 
spectrum on a screen in a dark room, he noted the segregation of certain 
species of Lepidoptera on the different colours. The red to the green 
portion of the spectrum exercised by far the greatest attraction. White 
lights, however, proved more attractive than any single isolated colour. 
Hewitz’s experiments (Dewitz, 1912 A), by means of lamps provided 
with glass screens of different colours, gave other results, as he found 
that the green proved the most effective. Dewitz and Vermorel {vide 
Dewitz, 1904) have conducted a long series of experiments with 
acetylene lamps, in order to determine the proportions of the sexes 
among Lepidoptera that were attracted. In the family of the Bomby- 
cidae only 4% of the moths attracted were females, among the Noctuidae 
19 "/o) ill the Geometridae 27 “/o) and in the Tineina 39 7o- Dewitz and 
Gastine {vide Gastine, 1903, p. 630) found that in the case of the moth 
PortJiesia chrysorrhoea there was a good deal of variation in the pro¬ 
portion of the sexes attracted. This was believed to be due to varying 
atmospheric conditions. Observations conducted by David and Laborde 
(Abstract in Rev. Applied Entom. Ser. A, Vol. l, 1913, p. 9), using 
1200 lanterns over an area of 270 acres, for a period of 17 days resulted 
in the destruction of about 100,000 various Lepidoptera of which 
approximately 40"/o were females. Although it was computed that only 
