D. Keilin 
443 
Another record on the habits of this very common species of Sarcophagid is 
contained in a short note of E. W. Bowell (1917), published in the Proceedings 
of the Malacological Society of London. The note is as follows: “ Some time since 
I found a number of dead and moribund II. itala on the common by Chipstead 
Station in Surrey which are apparently being destroyed by some dipterous 
larvae. Some of the imagines were bred out, and have kindly been identified 
by Mr K. G. Blair of the British Museum as Sarcophaga nigriventris Mead. The 
causes of the death among the Mollusca are so little understood that this 
identification seems worth recording.'' 
From several specimens of H. virgata killed by the larvae of Melinda 
cognata and also from dead and decomposed specimens of Theba cantiana I 
extracted the full-grown larvae of a Sarcophagid from which the adults of 
S. nigriventris were bred. On the other hand I never obtained this fly from 
H. itala which were collected in great numbers along the Grantchester Road. 
(c) Sa rcophaoa sp. probably S. crassimargo Band. 1 
There is not a single record in entomological literature of the life-history 
of this Sarcophagid. 
I found its larvae last year in a few specimens of H. virgata collected from 
a large colony of these snails living on grass along a garden fence on the 
Barton Road, Cambridge. 
The contents of the shells which harboured these larvae were reduced to a 
liquid putrefying mass, which, on a careful examination, showed also the 
chitinous remains of the mouth-parts, cuticle with spiracles, etc., of different 
stages of Melinda larvae. In one case, close to a Sarcophaga larva, I also found 
a recently killed larva of M. cognata which still contained all its internal 
organs. 
All this shows clearly that the larva of S. crassimargo invades the snail 
which has been previously parasitised and killed by the larvae of M. cognata 
and that it then kills these larvae and lives upon the decomposed remains of 
their host. 
The full-grown larva is 11 mm. long; it is composed of a pseudocephalon, 
three thoracic and eight abdominal segments, which bear numerous sinuous 
rows of small transparent and flattened hooks. The ventral side of the seg¬ 
ments is covered with numerous hemispherical projections each bearing the 
sensory organs in the form of a pit surrounded by a ring of thickened chitin. 
The remains of the thoracic legs of the larva are represented by six groups of 
sensory organs each composed of three very short hairs. The respiratory system 
is amphipneustic. The prothoracic spiracles end in 15 papillae (PI. XXV, 
fig. 22), the postabdominal, as is always the case in Sarcophagid larvae, lie in 
1 From the four pupae of this fly I obtained only one adult female. Unfortunately the 
females of Sarcophaga do not present very good characters for purposes of identification, though 
Mr Wainwright who examined this specimen found it to be almost certainly a $ of S. crassi 
mar go Pand. 
