EGG PARASITES OF THE BROWN -TAIL MOTH. 
257 
Three races or species have been reared from the eggs of the brown- 
tail mot h , two of them being European and the third American. 
The American, according to Mr. A. A. Girault, to whom the series of 
mounted individuals was submitted for determination, is the com- 
mon and widely distributed Trichogramma pretiosa Riley. One of the 
European, which is here referred to as the pretiosa-likc form, is or 
appears to be structurally identical with the American pretiosa. It 
differs in that the progeny of parthenogenetic or unfertilized females 
is either of both sexes, or else exclusively female, while the progeny 
of unfertilized females of the Americas species baa always been 
exclusively male in the very considerable number of reproduction 
experiments with such females which have been carried on at the 
laboratory . 
The other European species may at once be distinguished from either 
of its congeners by its dark color, as well as by other characters of 
taxononiic value. Like the American race of T. j>r< tinsa which was 
studied at the laboratory, it produced males exclusively as the 
result of parthenogenetic re- 
production. _ / y - . . 
1 1 seems to t he w liter that 
in the two morphologically 
identical but biologically dis- 
tinct races oi '1 richogra mma rm.U Eggs of the brown-tall moth, ft portion of 
( 7 luiliosd American Or Kll- which has Imvii jiura-sitizt'd l>y Trichogramma sp. 
1 I ' . Ll Original 
ro|)ean) w e have w hat is not h- 
ing Less than two species, quite as distinct as are the species of 
bacteria, for example, which are founded upon cultural characters. 
If the manner in which a bacterium reads when cultivated upon 
a certain medium prepared after a fixed formula may be considered 
as sufficient to separate it specifically from an otherwise indis- 
tinguishable form which reacts in a different manner under identical 
circumstances, why may not the same distinctions be made to apply 
to insects' It may not appeal to the taxonomisl and student in 
comparative insect morphology, but it certainly will appeal to the 
economic entomologist, who has, or ought to have, a greater interest 
in the biological than in the anatomical characteristics of the subjects 
of his investigations. The case of Trichogramma is by no means 
unique. That of Tachina mella, which is practically indistinguishable 
from T. larvarum but which reacts differently in its association with 
the gipsy moth, is another. Another is to be found in the American 
and European races of Parexorista chelonix. There are also others, 
which need not be mentioned here, but which will receive attention, 
it is hoped and intended, at some future time. 
These statements concerning the behavior of the several forms of 
Bpecies of the genus Trichogramma are based upon the results of 
95677°— Baa 1)1— n 17 
