NATURAL ENEMIES: PARASITIC INSECTS. 
147 
reared much later from other material. From 240 curculio larvae 
which entered the soil August 30 to October 15 there emerged 16 
specimens of rufus from September 24 to October 23. This gives a 
percentage of parasitism of 6.66. Xo other kinds of parasites emerged 
from these late larvae, while the proportion and number of rufus were 
larger than at any previous time. 
(Porizon) Thersilochus conotracheH Riley. 
This ichneumonid parasite of the curculio (see fig. 27) was 
described by Riley in 1871 (Third Missouri Report, p. 28) from speci- 
mens reared from cocoons sent him by Dr. Trimble, of Xew Jersey. 
The parasite feeds upon the curculio larva, and while developing 
to the adult form in the fall, remains in the cocoon until the following 
spring. This habit of ovenvintering in the soil perhaps has con- 
tributed to its general oversight by persons who have reared cur- 
culios, for there are very few references in literature concerning it. 
Five specimens of adults of this 
species were dissected from cocoons 
by Mr. Johnson, at Youngstown, 
X. Y., August 24 and October 2, 
1908, and on October 4 of the same 
year a total of 76 cocoons of this 
parasite was found in curculio rear- 
ing jars, in which had been placed 
a total of 836 curculio larvae, giv- 
ing a percentage of parasitism for 
this species of 9.09. Mr. John- 
son also succeeded in rearing this 
species from material kept over 
winter. On October 5, 1905, 55 cocoons were found in a jar for 
breeding curculios at Youngstown, X. Y. This jar was again exam- 
ined May 18, 1906, by which time 11 adult parasites had emerged. 
Forty-eight cocoons were found in a jar in which had been placed 549 
curculio larvae, at Xorth East, Pa., August 24, 1906. 
Dr. Riley evidently reared this species, along with (Sigalphus) 
Triaspis curculionis, in numbers in Missouri, for he speaks of having 
distributed specimens of each, from Kirkwood, to several localities. 
The insect is recorded by Dr. Howard from Coon Island, Pa., in 
1887, and Riley and Howard (Kept. Com. Agr., 1888, p. 64) refer 
to receipt of specimens from a correspondent who found them ovi- 
positing and regarded them as a new enemy of the plum. Prof. 
Gillette, in his curculio studies in Iowa, makes do reference to Pori- 
zon, which presumably was not observed. The species is probably 
of much less economic importance than the preceding, though, as 
FlG. 27.— (Porizon) Thrrsiloclius conotrachdi, 
parasitic upon the plum curculio: a, Fe- 
male; b, male. (From Riley.) 
