430 
ON THE LIFE-HISTORY AND LARVAL ANATOMY OF 
MELINDA COGNAT A MEIGEN (DIPTERA CALLIPHO- 
RINAE) PARASITIC IN THE SNAIL HELICELLA ( HELIO¬ 
MANES) VI EG AT A DA COSTA, WITH AN ACCOUNT OF 
THE OTHER DIPTERA LIVING UPON MOLLUSCS 1 . 
By D. KEILIN, Sc.D. 
(From the Quick Laboratory, University of Cambridge.) 
(With Plates XXII—XXV and 6 text-figures.) 
CONTENTS. 
PAGE 
Introduction . . . .• . . . . . 431 
I. Systematic position of the genus Melinda Rob.-Desv. and its re¬ 
lation to the genus Onesia Rob.-Desv. . . . . 431 
(а) Onesia characters of the genus and life-history . . . 432 
(б) Melinda characters of the genus and previous knowledge of 
life-history ......... 433 
II. Life-history of Melinda cognata Meigen parasitic in Helicella virgata 434 
(a) Host: H. virgata da Costa ....... 434 
( b ) Melinda cognata and its life-cycle ..... 435 
(c) Hymenoptera (Atractodes exilis Hal. and Exolytus petiolarius 
Thomson), hyperparasites of M. cognata . . . 437 
III. Description of early stages of M. cognata .438 
(а) Egg.438 
(б) First stage larva.438 
(c) Second stage larva.440 
(d) Third stage larva ..440 
(e) Puparium and pupa.442 
IV. Three other flies living upon Helicella virgata .... 442 
(а) Melinda sp. probably M. gentilis (R.-D.) Verrall (1912) . 442 
(б) Sarcophaga nigriventris Meigen ...... 442 
(c) Sarcophaga sp. probably S. crassimargo Pand. . . . 443 
V. Other Diptera feeding upon living and dead Molluscs . . . 444 
(1) Parasites .......... 444 
(2) Carnivorous ......... 445 
(3) Epizoic .......... 446 
(4) Saprophagous ......... 446 
Appendix. Observations of Mr E. Seguy on Musca domestica larvae 
devouring living snails . . . . . . . 451 
References ........... 452 
Explanation of Plates ......... 454 
1 Published with the aid of a grant from the Government Grant Committee, Royal Society. 
