96 
PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 
reason to believe that others among the introduced species will not 
disperse at an equal rate, once they are sufficiently well established. 
But Monodontomerus is eminently well fitted for dispersion, and 
its case is altogether different from that of a tachinid which is de- 
pendent upon sexual reproduction for the continuation of the spe- 
cies. A few hundred individuals, spreading rapidly toward all 
points of the compass, soon become widely scattered, and it is, and 
will remain for a long time, a question just how rare an insect may 
be and each individual still be able to find its mate. That the indi- 
viduals of the first colonies of many of the tachinid parasites scat- 
tered so widely as to make the mating of the next generation purely 
a matter of chance and of rare occurrence is now accepted as well 
within the bounds of probability. 
The first serious doubts as to the wisdom of the policy of the small 
colony were felt in 1907, and beginning with June of that year larger 
colonies were planted in the instance of every species than had been 
the practice up to that time. In the fall of 1908 the recovery of 
Monodontomerus over a wide territory lent strength to these half- 
formed convictions, and when, during 1909 and 1910, one after 
another of the various parasites were recovered under circumstances 
which were in most cases essentially similar, all doubts vanished as 
to the wisdom of the course finally adopted. At the present time 
there is no more inexorable rule governing the conduct of the labora- 
tory than that establishment of a newly introduced parasite is first 
to be secured, while dispersion, if later developments prove that it 
can be artificially aided, comes as a wholly secondary consideration. 
For the most part, however, dispersion may be left to take care of 
itself. 
An even larger appreciation of the necessity for strong colonies 
has been reached during the present winter (1910-11), coincidently 
with the results of the scouting work for Monodontomerus and 
Pteromalus in the brown-tail moth hibernating nests. (See maps, 
Pis. XXII, XXV.) The details will not be given in this imme- 
diate connection, but they will be found later on in connection 
with the discussion of these species. It is sufficient at this time to 
say that the circumstances under which the Pteromalus was recov- 
ered after the lapse of two years following its colonization were such 
as to cast doubts upon the conclusions which had been tentatively 
reached concerning the inability of certain other species to exist in 
America, and their possible significance had something to do with 
the decision to continue the work of parasite importation along 
wholly different lines in 1911. It may be, after all, that 40,000 
individuals of Apanteles fulviyes are not enough to make one good 
colony. - 
