444 
Melinda cognata Meigen 
a deep posterior groove of the last (eighth) abdominal segment. The external 
chitinous ring which surrounds each spiracle (PI. XXV, fig. 18) is not complete 
but interrupted near the scar (sc.). The three spiracular clefts are elongated 
and with their axes convergent towards this scar; the external openings of 
the perispiracular glands are exceedingly small. 
The Buccopharyngeal armature (PI. XXIV, fig. 11) is of the typical Cyclo- 
rhaphous form; the specific character here being the bilobed dorsal arm of the 
pharyngeal sclerite. All the other details of the structure of this organ are 
shown in the above mentioned figure. 
The puparium of this fly can be easily recognised as belonging to a Sarco- 
phagid by an examination of its posterior end which shows the spiracular pit. 
The prothoracic spiracles of the pupa are reduced to a pair of internal rosette¬ 
like organs which bear numerous papillae (Text-fig. 5) and which correspond 
to the internal spiracles of the Melinda pupa. The prothoracic spiracular 
horns, which in the latter protrude through the cuticle of the puparium, do 
not exist in this pupa nor in those of all the other Sarcophagids. 
Fig. 5. Prothoracic spiracle of the pupa of S. crassimargo Panel. /. c. felt-chamber; 
i.sp. internal spiracle; p. spiracular papillae; Tr. tracheal trunks. 
V. AN ACCOUNT OF ALL THE DIPTERA FEEDING UPON 
LIVING AND DEAD MOLLUSCS. 
A great number of Diptera have been recorded living upon Molluscs, but 
our knowledge of the life-history of these insects is still very unequal. Whereas 
for a few of them we have a complete account of their development, for many 
others we only know that they were obtained from a particular species of 
Mollusc. 
All these Diptera can be separated into four groups: (1) Parasitic, (2) Car¬ 
nivorous, (3) Epizoic, and (4) Saprophagous. 
(1) Parasitic Forms. 
The following species have been recorded as parasites of different snails: 
Chironomus sp., the larvae of which were recorded by Barnard (1911) 
as living in the mantle cavity of Limnea peregra Midler, collected in the foun- 
