226 PAKASITES OF GIPSY AND BROWN-TAIL MOTHS. 
This is one of the less striking of several examples of a species which 
differs from another in biological rather than in structural charac- 
teristics. Others are to be found in the European race of Tricho- 
gramma, in the Japanese Apanteles parasitic upon Euproctis con- 
spcrsa, which so resembles the brown-tail Apanteles of Europe, or in 
Parexorista chelonise, examples which will be again referred to on 
subsequent pages. 
The large, flattened, and conspicuous eggs characteristic of Tachina 
and its allies are the most, and in fact the only familiar type of tachinid 
eggs, and they are deposited before embryological development has 
taken place in at least a part of the instances which have come under 
direct observation. The larva issues through an irregular hole in one 
end, and immediately forces an entrance through the skin of its host. 
The life cycle is longer than in the case of Compsilura, but just how 
much longer is not known. Sometimes the larva is carried over into 
the pupa of its host, but not very often. Very frequently it kills the 
host after it has prepared for pupation. Nearly always it leaves the 
host remains before pupating, on its own account, but occasionally 
pup aria within the caterpillar skin or pupal shell are found. 
The puparium (PL XX, fig. 2), unfortunately, is practically insepa- 
rable from that of Tricholyga grandis or Parasetigena segregata in its 
structural details, so that it is necessary to rear the fry before the spe- 
cies can be determined. 
As a parasite of the gipsy moth, Tachina larvarum may and some- 
times does take preeminent rank. Caterpillars from Holland have 
been received from which more pup aria were secured than there were 
hosts, and the same has occurred on at least one other occasion in the 
instance of a box of caterpillars from Italy. When Tricholyga grandis 
is common, Tachina larvarum is rare, or at least has been rare in each 
instance in which the two species have been specifically determined 
as they issued from the imported material. It has also been entirely 
absent from some lots of caterpillars which did not produce Tricholyga. 
It was about the first, if not the very first, parasite to be received 
alive in the course of the parasite-introduction work, and mention 
will be found in Mr. Kirkland's first report as superintendent of moth 
work, of its having been reared from Italian material in 1905. It was 
not secured in sufficient abundance to make colonization possible 
until 1906, but in that year quite a number of small colonies was 
planted in various localities in the infested territory. In 1907 it was 
received, but in not such large numbers, and still smaller numbers 
were secured and colonized in 1908. In 1909, for the first time, really 
satisfactory colonies were planted, and one of these colonies was 
strengthened by the liberation of more individuals in 1910. 
So far as it has been possible to determine, no results followed these 
several attempts at colonization. Of all of the tachinids liberated in 
