172 Proceedings of the Royal Physical Society. 
Hapervment 3.—On 18th May another young holly plant, in a pot of soil, 
and with many eggs on its leaves, was subjected to fumigation under severer 
conditions. The strength of the cyanide was greater, and the plant during 
fumigation was placed, not exposed in a large fumigation chamber, but 
covered by a box that just fitted the plant, and had a capacity of 124 cubic 
feet. The capsule in which the hydrocyanic acid gas fumes were generated — 
was laid on the soil of the pot in which the holly was planted, and the fumes 
rose right up through the plant. The embryos in the eggs on this plant 
were well advanced; some of the eggs on the plant had already hatched 
before the experiment was done. After fumigation, twelve leaves bearing 
fourteen eggs were removed from the plant on 21st May and kept under 
observation. Nine of the eggs hatched in due course; in the other five the 
caterpillars had been killed. All the experiments were done at a temperature 
of 60°F. I am greatly obliged to Professor Gemmell for his courtesy 
in offering all the conveniences of his laboratory for these fumigation 
experiments. 
My thanks are due to Dr Stewart MacDougall for suggesting this 
research on Hudenis nevana, and for his unfailing kindly counsel in its 
prosecution, and especially for his help in the fumigation experiments. 
EXPLANATION OF PLATE. 
g.1. Holly leaf bearing a cocoon of Hudenis nevana, with moth. Natural size. 
Fig. 2. Leaf with cocoon from which empty pupa case protrudes. ; | 
igs. 3and 4. Male and female moth, both from life. x 4. 
Fig. 5. Eggs on holly leaf. x 4. 
Fig. 6. Holly shoot with leaves fastened together by larval webbing (see text). 
Fig. 7. Holly shoot at the end of larval life. The webbings have burst. 
I am indebted to Mr Hugh Main for the photographs which form Figs, 3, 4, and 5, 
and to Mr Richard Muir for those forming Figs. 1 and 2. 
(Issued separately, 7th December 1917.) 
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