July 29, 1918 
Parasites of the Brown-Tail Moth 
193 
were obtained for liberation in brown-tail-moth infestations. That these 
species are widely distributed in Europe was shown by the recovery of 
both parasites from webs that had been sent from the following countries: 
France, Netherlands, Germany, Russia, especially southern Russia, Aus¬ 
tria, Switzerland, and Italy. Once introduced into New England, both 
species became quickly established, so that after 1911 a large amount of 
material for colonization was obtained from caterpillars collected in local 
infestations. So rapid has been the spread of the parasites that, although 
up to the present only 150 colonies of the A pan teles and 20 of the Meteorus 
have been placed in 135 and 18 towns, respectively, no further coloniza¬ 
tion is necessary. Both parasites have been recovered from practically 
the entire brown-tail moth area, either by rearing from the brown-tail 
moth larvae in the early spring or by dissection from hibernating cater¬ 
pillars. 
In making collections of brown-tail-moth webs for the recovery of 
these parasites and to obtain material for colonization, whenever pos¬ 
sible 105 webs have been taken in each of a considerable number of 
towns some time during the winter and placed in cold storage until spring. 
One hundred of these were then placed in one of the large rearing trays 
(PI. 19, B), and the caterpillars fed. The foliage was placed upon 
mosquito netting that had been laid over the webs. The purpose of 
this was to draw the caterpillars away from their webs, so that the latter 
could be removed readily and destroyed by rolling back the netting 
with foliage and larvae. This greatly facilitated the picking over of the 
webs for the cocoons of the parasites. The remaining five webs were 
placed in small individual trays (PI. 19, C). The caterpillars in each 
of these single-web trays were counted, and since a count of the Apanteles 
and Meteorus cocoons removed later was also made, the extent of para¬ 
sitism by these two species at each locality was determined. 
When dissections were made for the recovery of the parasites, as in 
1917 and 1918, the work was done early in the year while the cater¬ 
pillars were still dormant. In 1917, the first year of systematic dis¬ 
section work for the recovery of brown-tail-moth parasites, 5 webs were 
taken from each of the collections that had been made the preceding 
fall or during the winter; from each of these webs 50 caterpillars were 
taken at random and dissected under the binocular microscope. Eater 
it seemed that dissecting a smaller number of caterpillars from a larger 
number of webs would give a better representation of actual parasite 
conditions. Accordingly, this year (1918) 20 brown-tail-moth larvae 
were dissected from each of 10 webs. This method of determining the 
extent of parasitism by making dissections probably gives more accurate 
data than rearing, since the somewhat unnatural conditions under which 
the caterpillars are fed in the spring must prevent the issuance of some 
of the parasites. Moreover, the dissections give data on the extent of 
