June, ’24] 
JAYNES: SELECTIVE PARASITISM 
367 
the feeding of a large number of Ochrosidia larvae upon the grass roots. 
A few Popillia larvae were found at this time but not in sufficient num¬ 
bers to cause damage to the sod. Thirty-eight female Tiphia 2 were 
collected in the vicinity of Moorestown at this time and placed in tins 
with Popillia larvae. The Tiphia laid 72 eggs, all of which they placed 
dorsally between the second and fourth segments. Several of these eggs 
hatched and the larvae partially developed; but with one exception 
never became sufficiently matured to spin perfect cocoons. One Popillia 
larva, upon which a Tiphia larva was feeding, was also found in the field. 
The parasite was situated between the second and third dorsal thoracic 
segments, and developed sufficiently to spin a perfect cocoon. This was 
the first case known of a Japanese beetle larva being parasitized in the 
field by a species of Tiphia. 
In the fall of 1922, several diggings were made to ascertain the num¬ 
ber of larvae present in the area where the injury to the sod has been 
observed and in adjacent areas. The area of each digging was usually one 
square yard made in representative portions of the field. It was found 
that there was an average of 151 Ochrosidia larvae, 8 Popillia larvae 
and 44 Tiphia cocoons to each square yard. Finding Tiphia cocoons at, 
this time indicated that the adults were present in considerable numbers-, 
during the summer although none was collected in this particular locality- 
except on wild carrot blossoms bordering the course. 
Experiments and Observations in 1923 
In the early spring of 1923, it was found that the number of Popillia 
larvae and Tiphia cocoons was about the same as in the fall although the 
Ochrosidia larvae were less numerous due to winter kill and disease, the 
highest mortality being found in the areas where the dead grass had 
been removed by rakings. At this time cocoons were found as numerous 
as 114 to each square yard, while there were only 56 Ochrosidia larvae in 
the same area. In another square yard, 27 cocoons and 211 Ochrosidia 
larvae were found. On further diggings over 3,000 cocoons were ob¬ 
tained at the Moorestown Golf Course in an area of 60 to 70 square 
yards. Finding such a large number of Tiphia cocoons is an unusual 
occurrence. 
Experiments were conducted to further determine whether the 
Tiphias would parasitize and successfully develop on the larvae of 
Popillia. The usual method of rearing the parasite was to place a single 
2 Most of these are T. punctata as far as we know, but it is very probable that at 
least another species or two may be present. 
