THE PARASITES OF POPILLIA JAPONICA 23 
In this manner about 800 grubs were inoculated in 1921 and 
7,800 the following year. The greater proportion of the flies col- 
lected in the field either contained eggs alone or had already deposited 
their larvae, so that the average number procured from each fly did 
not exceed 50. 
Upon completion of the field work for the season the parasitized 
grubs were forwarded to the Ri vert on laboratory. It was found as 
a result of these two years' work that the mortality in shipping from 
Japan and in holding the grubs under laboratory conditions through- 
out the winter was so great as to render the general method im- 
practicable. Late in 1922 a locality was found in Hokkaido where 
adult flies were abundant, and this gave promise of a fair percentage 
of parasitism in the overwintering grubs in the soil. An examina- 
tion of the field grubs in April of 1923 revealed an average parasitism 
of 10 per cent. Collections were consequently made of some 11,000 
grubs and these were shipped to New Jersey about the middle of 
June. At the time of collection it was not possible to distinguish 
between those parasitized and unparasitized, and consequently it 
was necessary to forward the entire lot. This method of importa- 
tion resulted much more satisfactorily, since approximately 70 per 
cent of the parasite larvae in the shipment yielded adults during 
July and August, at Riverton. 
LIFE HISTORY 
The young larva (fig. 20, F), after being deposited upon the soil, 
burrows about in search of host grubs, being guided probably by the 
sense of smell. When the host has been found the larva seeks out a 
crevice or suture in the integument and commences penetration, this 
being effected in one to two hours. It now lies free within the host 
body, surrounded by fluids and masses of fatty tissues. No permanent 
connection for respiratory purposes is made in this stage either with 
the tracheal system or through the derm. Early in the second stage, 
however, the caudal spiracles are attached to a main tracheal trunk 
near the thoracic or first abdominal spiracles of the host (fig. 21, A). 
The body is directed caudad, and feeding takes place largely in the 
mid-abdominal region. 
The second molt occurs ordinarily in the early spring, and at this 
time the dark chitinous respiratory funnel appears as a covering of 
the posterior segments of the larva. In some cases, where the point 
of attachment is very close to the spiracle, this funnel is dimly 
visible externally, but dissection is necessary for verification. Devel- 
opment in the final stage is very rapid, and the body of the host 
becomes more translucent in color, because of the consumption of the 
fat bodies which normally are present in large masses. The host 
remains alive and active until practically all of the body contents, 
aside from the vital organs, are consumed, though during the week 
preceding death evidence of life is presented only by a spasmodic 
twitching of the maxillae or legs. 
After the death of the host the Prosena larva tears a hole ventrallv 
in the integument of one of the distal segments of the abdomen, 
then severs its connection with the respiratory funnel, reverses its 
position, and completes feeding in the thoracic region. This being 
