148 
Psyche 
[June- August 
too expensive and unreliable.’ ’ Therefore he discontinued fur- 
ther experimenting along these lines. 
With the development of calcium cyanide during recent 
years, it was believed that these objections were eliminated. It 
is a product convenient to handle, easy to apply, less danger- 
ous, and much more economical. Its greatest asset, how-ever, is 
that the gas is not evolved suddenly and turbulently. When 
normal dosages are applied the chance of injury to living plant 
tissues is at a minimum, for the gas evolves gradually, the peak 
being reached some little time after the plant tissues have re- 
ceived small amounts of the gas produced soon after applica- 
tion. In the firm belief that calcium cyanide would succeed 
where the old process of sodium cyanide plus sulphuric acid 
had failed, the writer was sent to Europe in December, 1925, to 
investigate the possibility of control of Eudemis and Cochylis 
with Cyanogas calcium cyanide. 
As mentioned above, no adequate location could be found 
in Spain, due to the scarcity of the pests in that country. How- 
ever, two suitable sites were found, the first being near Bordeaux, 
France, the other in Lausanne, Switzerland. Dr. J. Feytaud, 
director of the Station Entomologique de Bordeaux, very kindly 
co-operated in the undertaking by allowing the use of his lab- 
oratory facilities and also permitting us to experiment in vine- 
yards under his charge. Similarly, Dr. H. Faes, director of the 
Station F6derale d’Essais Viticoles de Lausanne, courteously ex- 
tended the use of laboratory and vineyards. Both thus faci- 
litated the experimental work. 
Life Histories of the Pests. 
Before proceeding with the details of the experiments it is 
well to mention briefly the salient features in the life histories of 
these insects. Essentially they are alike, the only variation 
being that Clysia ambiguella (Cochylis) has two annual genera- 
tions, whereas Polychrosis botrana (Eudemis) has sometimes a 
partial and sometimes a full third generation. Both insects pass 
the winter as pupae within rather thick cocoons spun by the 
larvae. The cocoons are ordinarily attached to the vine stalks, 
although at times they have been found on rocks, fences, the 
