1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo Joo 
on snails, often entering the pulmonary cavity of Lymnza.! Most other 
leeches, too, probably at times attack mollusks. 
Species of Hydra, or stalked Infusoria of the family Vorticellidse 
(especially of the genus E’pistylis Ehrenberg), occasionally become fixed. 
upon the shell and it is believed that in some cases they are responsible 
for deformations or monstrosities.” | 
In an interesting paper Lundbeck?® has recently shown that certain 
small Huropean muscid flies of the family Sciomyzide live as larvee upon 
the contents of fluviatile snails, most probably attacking the live mollusk. 
His observations were made in Denmark where he found the pupa of 
Calobea bifasciella (Fallen) exclusively in Lymnzxa truncatula Miiller, 
closely attached within the aperture of the empty shell. The pupa of 
another species, Clenulus pectoralis (Zetterstedt), occurs in Planorbis 
vortex (Linneus), sometimes a whole whorl away from the aperture. The 
third species, Clenulus punctatus Lundbeck, was bred from several snails, 
most commonly from young specimens of Planorbis planorbis (Linnzeus), 
but also from P. albus Miiller, young P. corneus (Linnzeus), and Lymnzxa 
peregra. ‘There have been a few other incomplete records of dipterous 
larve attacking fresh-water snails.* 
Certain aquatic Coleoptera, especially Dytiscide, prey freely upon 
fluviatile snails. In Europe Dytiscus marginalis Linneeus is said to ‘prefer 
Lymnexa stagnalis to other species,’ although accumulations of the shells 
of Planorbis corneus with the sides of the whorls bitten away, to allow of 
easy access of the animal, have been recorded as the work of this beetle.® 
Aquatic snails must be an important item in the food of many am- 
phibians, such as frogs and others that leave the water but for short 
intervals. Unfortunately, little definite information is available at 
1See E. J. |acquet]. 1885. ‘Sur quelques parasites des Lymnées,’ Echange, I, p. 2. 
Elliott, W. T., 1917, Proc. Malacol. Soc. London, XII, p. 307. a 
2S3ee A. Brot, 1877, Ann. Soc. Malacol. Belgique, XII, Bull. Séances, p. xliii. 
Sykes, E.R. 1894. ‘Note on Limnea auricularia.’ Journ. of Malacol., III, pp. 34-36. 
Standen, R. 1899. ‘Remarks on the cause of abnormality in Planorbis spirorbis.’ Journ. 
Conchology, IX, pp. 216-217. 
3Lundbeck, W. 1923. ‘Some remarks on the biology of the Sciomyzide together with the descrip- 
tion of a new species of Ctenulus from Denmark.’ Vidensk. Medd. Dansk Naturh. Foren., LXXVI, 
. 101-109. 
she 4Pelseneer |1920, Mém. in-8° Ac. Sci. Belgique, (2) V, pp. 79 (fig. 24), 115 (fig. 79), and 584] figures: 
the larval tube of a ‘“‘ Chironomus”’ fixed upon the outside of the shell of Physa fontinalis and claims that 
this larva is responsible for a reduction of the digitations of the mantle edge and even for a bifurcation of 
the posterior end of the foot. From what we know of the habits of chironomid larve, itis very unlikely 
that this was a case of true parasitism. Larve of Chironomus sp. were also recorded by K. H. Barnard 
(1911, ‘Chironomid larve and watersnails.’ Ent. Monthly Mag., XLVII, pp. 76-78) as living in the 
mantle cavity of Lymnza peregra, in England, but this case too needs verification, especially with regard 
he feeding habits of the larva. 
oes Van eae T. 1919. ‘Insect larvee destroying Physa.’ Nautilus, XX XIII, pp. 71-72. Records 
finding in Iowa dead Physa integra Haldeman enveloped in what was pronounced to be an insect case. 
5J. W. Williams, 1889, Science Gossip, p. 280. According to H. Blunck (1916, Zool. Anzeig., X’ VI, 
p. 279) Dytiscus marginalis attacks every kind of aquatic animal that is not too swift or too small and 
icul dilection for mollusks. 
we w.. 1894-1900. ‘Monograph Land Freshw. Moll. Brit. Isl., Struct. Gen. Vol.,’ (Leeds), 
p. 419. 
