57 
APPENDED NOTE. 
Prof. V. Deprez has given, under the title "Une Invasion de Dasy- 
chira pudibunda," in the Annales de la Societe Entomologique de 
Belgique for 1895, pages 333-335, some account of an outbreak of a 
European species closely related to our white-marked tussock moth in 
the vicinity of Carlsbourg, in the years 1892 to 1895. 
Vigorous efforts were made by the authorities to put a stop to the 
work of the insect. The forestry administration employed a special oil, 
made in Germany, to cover the eggs and thus to asphyxiate them, and 
also made use of different methods for preventing the climbing of 
the trees by the caterpillars. Moreover, the inhabitants of the sur- 
rounding villages were requisitioned in May to collect the perfect 
insects. " Nevertheless," says Professor Deprez, "what can human 
means accomplish against such a prodigious quantity of enemies?'' 
"Happily," he says, "nature, always foresighted, has placed a remedy 
beside the evil, and the researches of the most eminent naturalists have 
established the law that when an injurious insect develops in abnormal 
numbers its parasites are but little behind it in becoming proportionally 
multiplied. Thus, with the species of which we are speaking we have 
noticed an increasing multiplication of its natural enemies — the Ich- 
neumon flies — which charge themselves with the duty of reducing con- 
siderably the number of the caterpillars, and often of reestablishing 
the equilibrium which had been broken for several years." 
Experiments were instituted to determine the increase of the para- 
sites. In the winter of 1892-93, among 200 chrysalids, 30 were found 
to have been parasitized. A year later, from the same number, 53 were 
parasitized. A year later, in the winter of 1891-95, from the same 
number, 95 were found to be parasitized. 
How far this instance falls, in the completeness of the parasitism, 
below the instance which we have described in the foregoing pages 
will at once be evident. His concluding paragraph, freely translated, 
reads: "Will this proportion of the parasites increase still further dur- 
ing following years, as has been noticed in other countries, so as to 
bring about the complete stoppage of this unusual outbreak of the 
caterpillars, or will the parasites themselves be destroyed by other 
parasites, which, limiting their destructive action, will thus prolong 
the caterpillar invasion ? Future observations will determine." 
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