94 | BULLETIN 766, U. S. DEPARTMENT OF AGRICULTURE. 
further development of the parasite larva, but pupation will be ac- 
celerated. The larva can not remain in its tracheal funnel after the 
body contents of the host become flaccid, but it will be seen moving 
slowly about, and will emerge from two to five days after the death 
of the host. | 
Similar experiments were conducted during the years 1915 and 
1916 with brown-tail moth larve, treated in the same manner as were 
the gipsy-moth larve, with the average result of two parasites per 
larva, at times as many as four puparia being secured from one host. 
SUPERNUMERARY PARASITISM. 
The fight for ascendancy between some of the tachinid and hymen- 
cpterous parasites is wel] illustrated by a study of Compsilura para- 
sitizing brown-tail moth larve. When two internal feeding parasites 
of different orders occur in a single host larva and complete that part 
cf their existence which is passed within the host, parasitism is de- 
scribed as “supernumerary.” This is illustrated by Compsilura and 
Meteorus versicolor Vier. in their occurrence in brown-tail moth 
larve. It was noted, in an experiment where brown-tail moth larve 
were isolated and fed in single boxes, that J/eteorus versicolor was 
present to quite an appreciable extent. The hosts did not die imme- 
diately after emergence of this hymenopterous parasite, and in from 
two to four days, in some cases, Compsilura would emerge. In no 
case were any Compsilura secured previous to emergence of Meteorus. 
ECONOMIC IMPORTANCE. 
The white-marked tussock moth, Hemerocampa leucostigma, which 
a few years ago was a serious pest in many localities in New Eng- 
land, has practically disappeared since Compsilura was established. 
The saturniid Callosamia promethea, which in past years was very 
common in the area covered by Compsilura, is now quite rare. While 
the cabbage worm, Pontia rapae, is still a serious pest, its numbers 
have been materially lessened in some sections, Compsilura, no doubt, 
playing an important part in this decrease. The celery worm, Papilio 
polyxenes, 1s not so common now as it was previous to the importa- 
tion of Compsilura. The fall webworm, YWyphantria cunea, which 
could be found in eastern Massachusetts in large numbers in 1910, 
is scarcely noticed now. The writer dces not claim that Compsilura 
is the sole cause of the disappearance of these pests, but this parasite 
has been reared from all of them, and it is significant that the de- 
crease has occurred since the advent of Compsilura. Outside of the 
area in which this parasite occurs, many of these caterpillars will 
be found in considerable abundance. The gipsy moth and brown- | 
tail moth infestation has been materially lessened in sections where 
‘ORR Epa neato he bot 
