Article beginning on page 39.
Psyche 5:39-40, 1888.

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PSYCHE.
A NEW PARASITE OF THE HESSIAN FLY.
BY STEPHEN ALFRED FORBES, CHAMPAIGN, ILL. Parasitism of the winter brood of the
Hessian fly has been but rarely and
doubtfully reported, and so far as I
know, has not hitherto been strictly
authenticated. An observation re-
corded by Prof. Herrick in 184i1,
probably referring to the parasite now
known as Platygaster herrickii,
Pack., implies an abundant develop-
ment of that species in the hibernating
generation of the "fly," but this obser- vation was almost certainly incorrect
in some respects,-as has been shown
by Mr. Ho~ard,~-and has not been
verified in this piirticular.
The breeding of unknown parasites
from infested wheat in spring WEIS re-
ported by the writer in 1885 but the
breeding cage management in this case
was not such as to make it certain
that these were derived from the
Hessian fly. The following instance
is, consequently, probably the first to
estiiblish clearly the occurrence of this phenomenon.
From ;I field of wheat sowed after
o~ts and corn in the autumn of 1886,
living plants containing numerous pu-
p:iria of the Hessian fly were sent to
me Mar. I j, 1887, by my correspond-
ent Siimuel Bartley, Esq., of Edge-
w~od, in southern Illinois. A number
--
' Herrick, C : E. A briei prelin~inary account of the hessian-fly and its parasites.
(Amer. journ. sci. and
arts, 1841, v. 41, p. 153.158). p. 157.
* 3 loward, L. 0.
(3d rept. U. S. entom. comrn., 1885,
p. 219, foot note.)
3Forties, S. A. (14th rept. State entom. Ill., p. 46, Clot-note.)
of these puparia were enclosed in a dry
vial ; and from them seven images of
Cecidonzyia destructor emerged previ-
ous to the 23d of April. This vial
was not again examined until Oct. 18,
when seven proctotrupid parasites were
found in it-all dead. These belonged
to the genus PZatygaster, as limited
by Foerster and Tl~omson,~ and to a
species apparently undescribed.
General surface smooth, shining
black; head opaque, very slightly
pubescent, not cuboid, wider than
thorax, nearly twice as wide as long.
Temples narrow, vertex not margined,
but minutely transversely rugulose.
Front also transversely con ugated above the antennae, this corrugation merging
in a general irregular lineation of the
face. Upper half of front regularly
convex, lower with a slight vertical
carina commencing between the bases
of the antennae. Ocelli not elevated,
lateral ones equidistant from the eye
and the median ocellus.
Thorax short, deep, very convex, not
compressed ; prothorax minutely trans-
versely lineate at the sides; ineso-
thorax shining, ovate, broadest just
before wings, dorsum bare in middle,
elsewhere with sparse gray hairs, sides
more hairy in front. Parapsidal
grooves scarcely visible. Scutelluin
semi-circular, vaulted, nearly hemi-
spherical, without angle or process,
^Foerster, A. Hymenopterologische studien, heft 2, 1850, p. 108 and n5.
~Thomson, C. G. Sveriges ptotruper. (6fvers. af Kongl. vetensk.-akad. fdrhan I., 1859,~. 16, p. 69-87) P. 83.




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40 PSYCHE. [ April 1888.
conspicuously hairy in front and at
sides, bare and shining in middle ; sepa- rated from n~esoscutum by a rather
, deep transverse groove with two large
coarsely punctate and hairy foveae.
Dorsal outline of thorax consequently
broken at sc~~tellum. Tegulae shining,
smooth, slightly embrowned. Meta-
thorax hairy above and on sides.
Abdomen obovate, not narrowed at
tip, smooth, shining, except first seg-
ment, which is covered with long gray
hairs above and beneath, and the tip of
the abdomen, which is slightly hairy at
posterior edges of segments. Second
segment with elongate basal foveae
above, and a longitudinal basal groove
on each side beneath, slightly concave
to the margin, and extending two-
thirds the length of the segment.
absence of the reticulate finish of the
surface characteristic of P. herrich
-by the shorter and more vaulted
thorax, by the corrugated, narrower,
and more convex vertex, and the
narrower temples,-the head having
a less cnboidal form,-but especially in
the parapsidti1 grooves, which in Ra-
Antennae ten-jointed, black, with
scape long, sinuous, and not clavate,
and reaching to top of head. Club
five-jointed in female, six-jointed in
male, not compressed, more hairy than
scape and funicle. First joint of latter obovate ; second small, one-half to one- third the third,-the latter excurved
and obliquely truncate in male, similar
to fourth in female. First joint of club obconical, remaining joints, except the
last, quadrate, nearly equal in length,
about two-thirds as wide as long. Last
joint in femle ovate, obtuse, not much
longer than the preceding : in male
tygaster hewickii nre very large and
distinct, and in P. hiemalis are barely
visible in the most favorable light.
From P. mimitus, very briefly cle-
scribed by Lindeimat~,~ it differs in size, and conspicuously so in the proportiocs
of the an tennal segmen ts,-Lindeman's
species being only .5 mm. in length,
and the antenna1 scape about twice as
long as the first joint of the flagellum. 6 Lindeman, K.
Die pteroinalinen der hessenfliege,
cecidomyia destructor Say.
(Bull. Soc. imp&. natur
Moscou, 1887, no. I, 177-192.)
Separzite, p. 12.
narrower, acute, nearly twice as long
as preceding.
Head, thorax, and abdomen black
throughout. Anterior legs yellowish
shaded with fuscous, except coxae and
distal joint of tarsi, which are black on all the legs. Middle legs darker, hind
legs black, except tarsi and band at
upper end of tibia. Upper surface
of all the femora black. Wings extend-
ing far beyond the abdomen, hyaline,
iridescent.
Total length of head and body .g4
mm. ; fore wings .84 min. long, .35
mm. wide. Head .35 mm. wide, ..185
mm. long ; thorax .36 mm. long, .29
mm. wide, and .30 mm. deep. Ab-
domen of female .46 mm. long, .30
mm. wide.
This species differs from Platvg'aster
herrickii (authentic specimens of
which Mr. L. 0. Howard has kindly
sent me) chiefly in its much smaller
size, more shining aspect,-due to the




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