200 
Journal of Agricultural Research 
Yol. XIV, No. s 
Between this date and the time of oviposition in the hibernating cater¬ 
pillars of the brown-tail moth there is a period of more than a month, or 
ample time for another generation. Furthermore, at this time there are 
in the field a number of species that would seem to be desirable hosts, 
including the caterpillars of Hemerocampa leucostigma Smith and Abbot, 
Notolophus antiqua Linnaeus, Datana ministra Drury, Hyphantria cunea 
Drury, Apatela hasta Guen£e, and others. Experiments have been car¬ 
ried on in the laboratory with a number of known and unknown species, 
the caterpillars being reared from eggs and hence parasite-free at the 
time of their subjection to A . lacteicolor. In addition, field collections of 
first and second stage larvae of various possible host species have been 
made, and these reared for the recovery of the Apanteles. In the lab¬ 
oratory reproduction has been secured upon Apatela hasta Guen£e, 
Schizura unicornis Smith and Abbot, Hemerocampa leucostigma Smith 
and Abbot, and an undetermined arctiid. First-stage larvae of Apatela 
hasta were very eagerly attacked by Apanteles lacteicolor , as were also 
first-stage larvae of the Schizura unicornis and of the undetermined 
arctiid. In 1910 A. lacteicolor was recovered in the field from Datana 
ministra and Hyphantria cunea (j, p . 28g ), and during the past summer 
the writer has recovered it from Apatela hasta , a noctuid not uncommon 
upon wild black cherry and the species upon which A. lacteicolor repro¬ 
duced so readily in the laboratory. Further evidence of the probable 
importance of Apatela hasta as a host of A. lacteicolor was the collection 
of cocoons of the parasite, during the last-week of July, upon wild black 
cherry where only A. hasta was present in numbers. This species can 
be found in virtually all stages throughout the month of July, and, to 
judge from observations in the field and laboratory, the writer believes 
it to be an admirable host for tiding A. lacteicolor over the period elapsing 
before the brown-tail-moth caterpillars that are to carry the parasite 
over the winter become available. 
ECONOMIC IMPORTANCE OF APANTELES LACTEICOLOR 
As a control agent A. lacteicolor must take high rank. First, it is a 
very effective parasite of the brown-tail moth, as high as 20 to 25 per cent 
of the larvse of a web often being parasitized by this species. Then the 
facts that there are several generations annually, and that it is a parasite 
of more or less importance upon the gipsy moth and upon certain native 
injurious species, add to its value. In addition, A. lacteicolor destroys its 
hosts in the early stages, and thus prevents any considerable feeding by 
the individuals parasitized, since these are very greatly retarded. Plate 
21, D, shows a parasitized and an unparasitized caterpillar of an undeter¬ 
mined arctiid hatched on the same day from the same egg mass and 
similarly fed. Actual measurements in a number of cases showed that 
the individuals parasitized by A. lacteicolor eat, on the average, about 
one-fourth as much foliage as caterpillars of the same species and the same 
