DEVELOPMENT OF A HYMENOPTEROUS PARASITE 545 
NaOH, the muscles often separated from the hypodermis, in 
which case the rupture always occurred along the base of the 
hypodermis at the point where it connects with the muscles. 
This happened so frequently that it could not be considered 
accidental. 
In the Cucujid larva and larvae of Porthetria dispar, Simulium, 
and Calliphora erythrocephala, the muscle attachments are of 
the same nature as those in the Tabanid larvae, the insertion in 
every case being to the hypodermal cells which always possess 
hypodermal fibrillae within their cytoplasm. In none of these 
forms, however, could I detect dermal fibrillae. 
THE SEMIPUPA 
The semipupa marks a transition between the tracheate larva 
and the completed pupal stage. Still it belongs with the pupal 
stage, for the larval activities have ceased and the form of the 
imago has begun to develop beneath its old larval integument. 
Figure 6 shows the dorsal aspect of the semipupa, the circular 
areas marking the position of the abdominal tubercles which 
have collapsed, owing to the degeneration of the imaginal discs 
beneath them. 
Just prior to pupation, the tracheate larva crawls toward the 
anterior end of the fly pupa, now reduced to a mere flattened 
mass of cuticle, so that its head lies near the end of the puparium. 
In this position, the semipupal stage is attained which soon 
completes an ecdysis, voids the dark meconial mass, and becomes 
a fully formed pupa. 
THE PUPA 
The pupa of Spalangia does not differ from the usual hymen- 
opterous type and will not be described here. 
EFFECT OF THE PARASITE UPON THE HOST 
The parasite slowly consumes the blood plasma and its cellu- 
lar content of the host, reducing the latter to a flattened mass 
of cuticle. Fat vacuoles, albuminous bodies, accumulations of 
blood plasma and what is apparently the cytoplasm of the adipo- 
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