April, ’18] 
McCONNELL: A PARASITE OF THE HESSIAN FLY 
173 
paratively large, convex anteriorly, and slightly narrower than the pro thorax. The 
body color is grayish white, with very pale brownish head and large brownish black 
mandibles, which are simple curved hooks. The body and head are provided with 
long hairs, as is the mature larva. 
The mature larvse (Fig. 8, 2) vary greatly in size, but average about 2.75 mm. in 
length. They are white, with dark brown mandibles. The body is of the usual 
chalcidoid form, somewhat spindleshaped and concave ventrally. Head short, con¬ 
vex, without tubercles, slightly higher than wide, and partially immersed in the pro¬ 
thorax. Antennae not jointed, cylindrical, with bluntly rounded apex. Mandibles 
simple, curved, heavily chitinized hooks, with dorsal and ventral articular processes 
(Fig. 8, 5). The labrum and the region dorsal to it form a concavity (Fig. 8, 3), 
the central part of the labrum being heavily chitinized (Fig. 8, 4, b ) and bearing 
teeth on its ventral edge. These teeth are triangular and a little over 0.003 mm. 
long. They are irregular in number and arrangement, varying in number from 6 
to 9 and are separated by interspaces usually at least as wide as the height of the 
teeth. The lateral regions of the labrum are very thinly chitinized and the mandi¬ 
bular processes (Fig. 8, 4, c) are difficult to see. The maxillae (Fig. 8, 3) are thin 
and transparent and separated from the labium by a shallow notch. Each maxilla 
bears a cluster of three very small tubercles which probably represent the palpus. 
The labium is also thin and transparent and bears two pairs of very small tubercles 
probably representing the labial palpi. The head bears 8 long hairs; one pair sub¬ 
median on the dorsal posterior part of the epicranium; one pair between and slightly 
below the level of the antennae; another pair in the same plane posterior to the 
above; and a fourth pair ventral to the last and a short distance posterior to the 
mandibles. In addition there is a pair of small hairs dorsal to the labrum. 
The body consists of the usual 13 segments. Spiracles are present on the last two 
thoracic and first seven abdominal segments. Prothorax with 7 pairs of long hairs; 
3 dorsal, 1 lateral and 3 ventral. Mesothorax with 6 pairs of hairs: 2 dorsal, 1 lateral, 
and 3 ventral. Metathorax with 4 pairs of hairs: 1 dorsal, 1 lateral and 2 ventral. 
The thoracic hairs are all long except the dorsal metathoracic pair. Abdominal seg¬ 
ments 1-9 each bear a pair of subdorsal hairs and a pair of lateral hairs. Segments 
5-9 have in addition a pair of ventral hairs. Segment 10 bears 4 short bristles on the 
dorsal lobe and 2 on the ventral lobe. The abdominal hairs are all much shorter 
than those on the head and thorax, but increase in length on segments 8 and 9. 
The young larvse soon attach themselves to the host by means of 
the mandibles and use the tip of the abdomen to help anchor the body. 
They crawl with a leech-like movement, and when disturbed frequently 
retain their hold on the host by means of the mandibles and sway the 
body about the head as a fixed point. 
Explanation of Figure 8) 
Fig. 8, 1. Egg x 230, a Pedicel, b, Flagellum. 2. Mature larva, lateral view x 50, 
a Antenna. 3. Head of larva, ventral view x 216, a, Labrum, b Mandible, c Maxilla, 
d Maxillary palpus, e Labium, / Labial palpus. 4. Labrum, cephalic view x 960, a 
Toothed region, b Heavily chitinized concave area, c Mandibular process, d Angle of 
mouth. 5. Mandible, ventral view x 750, a Ventral articular process. 6. Pupa, 
lateral view x 40. 7. Adult female, dorsal view x 40. 8. Adult female, lateral view 
x 40. All figures have been reduced one-half. Drawings 6-8 have been made by 
Miss E. H. Hart. 
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