49 
to find a healthy caterpillar which one of the parasites was not engaged 
in stinging". The rearings which were undertaken at this time show a 
parasitism of perhaps 90 per cent of the caterpillars. 
The species principally involved in this work were Pimpla inquisitor 
and Chalcis ovata, both primary parasites. The remaining species were 
not abundant and very few hyperparasites were reared in the autumn 
of 1S95. It is worthy of record, however, that many caterpillars were 
killed at this time by some disease the nature of which has not as yet 
been ascertained, although some work has been done upon it by Mr. 
A. F. Woods. About 10 per cent of the cocoons at the end of Sep- 
tember gave forth adult moths, and of these, of course, only about one- 
half were females. Ten per cent, then, of the possible females of the 
fall generation laid their eggs, and the majority of these eggs hiber- 
nated successfully, so that in April and May, 1896, there was a moder- 
ately abundant hatching of young Orgyia caterpillars. 
In the meantime, however, the extremely abundant primary parasites 
had successfully hibernated and were in position to make their presence 
felt. It resulted that at the points of observation this first generation 
of tussock-moth caterpillars was practically exterminated, and in June 
it was a very difficult matter to find enough living individuals to carry 
on rearing-cage experiments at the very points where they had been 
present the previous year by thousands and thousands. Rearing-cage 
experiments at this time showed the actual percentage of parasitism to 
reach above 98 per cent. The details of one of these experiments 
follows: 
On June 30 and July 8, 189G, 621 cocoons of the tussock moth were 
collected without discrimination from the trunks of trees in the U. S. 
Department of Agriculture park. From these 621 cocoons issued the 
following parasites: 
Specimens. 
Pimpla inquisitor 729 
Bathy thrix pimplie 13 
Linmeria valida 1 
Theronia fulvescens 1 
Chalcis ovata . 69 
Dibrachys boucbeanus ' 50 
Asecodes albitarsis 1 
Frontina aletia* 7 
Frontina frencbii 14 
Tachina mella 12 
Euphoroeera claripennis 15 
Exorista griseomicans 4 
Total ' 916 
Thus from the 624 cocoons were reared 916 parasites, all but 61 of 
which were primary. Of moths 12 were reared, and with the excep- 
tion of these 12, all of the others which were not parasitized, and these 
'Estimated. 
11859— No. 5 1 
