472 Bulletin American Museum of Natural History [Vol. LIII 
its posterior end, bearing the spiracles, protruding into the mantle cavity; 
later the larva, having destroyed the kidney, attacks the liver and finally 
all the other organs of its victims. About that time the snail dies and shortly 
afterward the full-grown larva leaves the shell and penetrates into the 
earth, where it becomes a puparium from which about fourteen days later 
the adult fly emerges. The life-history of most of the other dipterous 
parasites of mollusks still remains to be worked out. They should be 
carefully distinguished from the numerous saprophagous or scavenger 
species which merely oviposit on dead snails and slugs. Phorid espe- 
cially may be bred in large numbers from decaying mollusks. The re- 
markable epizoic Phoridee (Wandolleckia) which occur upon the African 
forest Achatine have been treated by the junior author in the ‘Review 
of Congo Land Mollusks.”! 
In connection with the internal parasites of terrestrial snails and 
slugs mention should be made of the various Protozoa? and worms that 
are found in them. The worms usually are larve of cestodes or 
trematodes that later reach the adult stage in snail-eating vertebrates, 
particularly in certain birds. Certain nematodes too (fhadbitis) are 
known to inhabit the intestine of Arzon and the salivary glands of Limazx 
agrestts. 
Several species of mites (Acarina) infest land mollusks. They are 
commonly found on Limax maximus and on several of the European 
Helicide, retiring upon occasion into the pulmonary chamber.* The 
junior author also found mites, together with Wandolleckia, on a large 
Achatina of the Semliki forest. 
Ants have also been accused of destroying snails,* but we have not 
been able to find observations showing this to be actually the case. The 
shells, which are frequently found on or near the mounds of certain ants, 
are probably dead specimens gathered, together with pebbles, bits of 
wood, etc., in order to build a protective cover at the entrance of the nest. 
The vertebrate enemies of terrestrial mollusks are rather numerous, 
as snails and slugs “constitute a favorite and nourishing food for many 
animals, their defenceless conditions and sluggish movements rendering 
them an easy prey to many creatures besides man, their only protection 
being the distastefulness of certain species, or their power of concealment, 
oe prone Mus. Nat. Hist., XL, pp. 61-63. 
_ see Kithn, M. 1911. ‘Die Trypanoplasmen und deren Verbreitung in einheimisch - 
landischen Schnecken.’ Schrift. Phys.-dkon. Ges. Kénigsberg, LII, 1, AD. Roe oo ee 
3A. H. Cooke. 1895. ‘Molluses’ (Cambridge Natural History, III), p. 62. 
a cee A. K. 1920. ‘Vitrea and Pyramidula destroyed by ants.’ Journ. of Conchology, XVI, 
