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SOME EXPERIMENTS ON FLACHERIE IN THE GYPSY MOTH.' 
BY WILLIAM REIFF, HARVARD UNIVERSITY. 
In Volume XXVI, Nos. 13, 14, 15, and 16 of the “ Biologisches Centralblatt”’ 
(Leipzig 1906) Dr. E. Fischer of Ziirich has published some important studies on the 
susceptibility of caterpillars to diseases. In his investigations he has taken ex- 
traordinary care in establishing the primary causes leading to the disease variously 
known as “flacherie,” “flaccidenza” and ‘‘caterpillar-cholera,” a disease which 
deserves special attention on account of its extreme infectiousness. He has pointed 
out that the first tendency toward the disease lies in a decrease in the nutritive value 
of the food of the caterpillars, which suddenly induces a disturbance in metabolism. 
As a result the organisms responsible for the disease immediately find conditions 
suitable for their growth. One of the main causes of the disease is therefore to be 
sought in the susceptibility of the caterpillars, while the specific infection of flacherie 
is to be regarded as coming more or less secondarily; in other words, without sus- 
ceptibility infection cannot take place, and this susceptibility can be brought about 
by insufficient nourishment. In his experiments Fischer produced the proper 
susceptibility by giving the caterpillars food which he placed in water and renewed 
only every three or four days. This treatment causes an injury to the leaf protoplasm 
resulting from the presence of too much water. Before the visible outbreak of the 
disease he could recognize as an early symptom, a characteristic sweet odor in the 
breeding cages, which could be compared to that of withered lilac blossoms. When- 
ever this odor was noticeable flacherie soon made its appearance and as it progressed 
the odor increased proportionately. It is a well known fact that in the occurrence 
of Psilura monacha, the Nun, (‘die Nonne” of the Germans) in unusual numbers 
in Germany the only relief has come through the outbreaks of flacherie. Fischer 
therefore recommended, after the completion of his experiments, the artificial pro- 
duction of flacherie by intentionally giving the larvee poor food as soon as the abun- 
dance of Psilura monacha was noted in any particular locality. 
1 Contributions from the Entomological Laboratory of the Bussey Institution, Harvard University, 
INOS. 
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