TACHINID PARASITES OF THE GIPSY MOTH. hh | 
Hardly was the final establishment of what was for a few days 
considered to be the first satisfactory colony of Compsilura concin- 
nata accomplished than the necessity for the expenditure of further 
labor on its account was obviated by the discovery that it could be 
recovered from the field in small but at the same time in very satis- 
factory numbers. Only an insignificant number was reared from the 
collections of gipsy-moth caterpillars made in 1909, but later in the 
fall of that year field men who were scouting for evidences of the 
spread of Calosoma and searching under burlap bands for its molted 
larval skins began to bring into the laboratory bona fide puparia of 
Compsilura found under the same circumstances. It was thus pos- 
sible to delimit its range with some accuracy, and it was found to 
extend over a considerable territory, with the 1906-7 colony in 
Saugus much nearer to its center than any other more recently 
located colony. (See fig. 42.) There could be no doubt that the 
species was well established and spreading and multiplying at a rapid 
rate. 
The results of the season of 1910 were awaited with very great 
interest, in expectation that they would confirm those of the year 
before. That these were confirmed, and most conclusively and 
satisfactorily, is evidenced by the results of the rearing work as 
summarized in Tables IV and V (pp. 141, 142), which give the 
results of rearing work for that year. The total number of the 
parasites reared or otherwise recovered from the field as indicated 
by these tables is very far short of the total secured. 
Compsilura concinnata is recorded as a parasite of a large number 
of hosts in Europe, and will doubtless be found to attack an equally 
large number in America when it shall have become thoroughly 
established and abundant over a wide territory. Already some half 
dozen native hosts are known, and it would easily be possible to 
double or treble this list in the course of another season’s work, 
should it be conducted with that end in view. 
Few subjects for speculation are so overcrowded with possibilities 
as that of the effect which the importation of new parasites having 
a wide range of hosts will have upon native parasites and their hosts. 
The increasing abundance of Compsilura offers a most excellent 
opportunity to answer numerous questions which naturally arise 
when this subject is considered, and it is hoped that it may be made 
the most of. Already several highly significant observations have 
been made. 
One of the most interesting of these resulted from a series of col- 
lections of tussock-moth caterpillars made by Mr. Wooldridge in 
the summer of 1910 for the purpose of determining the prevalence 
of parasitism in various localities and under slightly different condi- 
tions. All of these collections were of necessity made under urban 
