July 29, 1918 
Parasites of the Brown-Tail Moth 
195 
The anterior pair have the coxae black, the trochanters and extreme base of the femora 
dusky, the remainder of the femora, the tibiae, and the tarsi yellowish; the middle 
legs have the coxae, the trochanters, and the basal two-thirds of the femora black, 
and the apical half of the tibiae dusky, the base of the tibiae and the tarsi yellow; the 
posterior pair have the coxae, trochanters, femora, and the apical half of the tibiae 
black, and the tarsi blackish, except the extreme base of the basal segment, which is 
yellowish. 
Abdomen: Somewhat shorter than thorax, entirely black; first and second tergites 
coarsely rugose; the first long, scarcely wider at apex than at base, and usually with 
a small, indistinct, shining median fovea on its apical half; the second tergite is trans¬ 
verse, three to four times as broad as long down the middle, the posterior margin 
arcuate; the broad lateral membranous margins on the apical one-third of the first 
tergite, and along the second blackish; third tergite and beyond smooth and shining. 
The ovipositor is long, almost half as long as the abdomen. 
SEASONAL AND LIFE) HISTORY OR APANTE)LE)S LACTEICOLOR 
THE EGG 
The female oiApanteles lacteicolor (PI. 20, A) oviposits in first and second 
stage brown-tail-moth caterpillars during the month of August. The 
very small larvae, those being but two or three days from the egg, are 
preferred, often being attacked while still on the egg cluster, before they 
have fed at all. The egg of the parasite (PI. 20, B) is a minute trans¬ 
parent object, measuring but 0.35 mm. in length, including the stalk at 
the end opposite the micropile. No particular part of the body of the 
host is selected for oviposition, the attack being merely a nervous thrust, 
requiring about one second, into any part of the caterpillar. Only a 
single egg is deposited at one oviposition, and usually only one egg is 
placed in a caterpillar. The parasite will oviposit from a dozen to 25 
times in quick succession if hosts are available, and will then rest for a 
period, sometimes for a day or two, before depositing more eggs. Ovi¬ 
position may extend over a period of several weeks, and a single female 
may attack upwards of 300 caterpillars, although under field conditions 
the average appears to be much lower, probably due in large part to the 
fact that the insect is delicate and rather short lived. In the laboratory 
one female, over a period of two weeks, oviposited in 320 larvae, placing 
two and even three eggs in some of these. That an egg was being de¬ 
posited with each thrust of the ovipositor was determined by dissecting 
from time to time caterpillars that had been attacked by the parasite. 
HIBERNATING LARVA OR APANTELES LACTEICOLOR 
The egg of Apanteles lacteicolor , having increased somewhat in size, 
hatches after about three days, and the young parasitic larva, free in 
the body cavity of its host, feeds slightly on the fat and lymph there, 
merely keeping pace with the very slow development of the caterpillar 
prior to hibernation. The position of this first-stage larva within its 
host varies, but more commonly the young A. lacteicolor is found in 
the posterior half of the body. As dissected from the hibernating 
