NEW YORK SHELL CLUB NOTES No. 232 May 1977 Page 5 
ern Scotland on account of its susceptibility to winter frosts 
(Evans, 1972). Microclimatically, it is probably in this sense 
that we should explain the fact that H. aspersa never establishes 
itself beyond the limits of irrigated plots. 
As to food plants, Helix aspersa is little selective. In captivit 
it was found to eat out of the 197 different kinds of food ee 
fered (Taylor, 1910) as compared to 54 eaten by Cepaea hortensis 
and 26 by C. nemoralis. In addition to living plants, the food of 
Helix aspersa consists of dead or decayed vegetation and other or- 
ganic matter in the soil. The snail prefers habitats rich in organ- 
ic waste matter and tolerates the pollution resulting from human 
activity. In this respect it is proper to quote Alvarez (1969): 
"The human influence is not always negative. On some species it 
has such a favourable effect, that within a few years only they re- 
main in human company... This is the case, for instance, with 
Helix aspersa, even though it is consumed in large numbers." 
Another feature worth mentioning here is the high rate of reproduc- 
tion. Only a few individuals need to be transported to a favourable 
new site. The mutual fertilization of these hermaphrodites and high 
rate of reproduction (Mienis, 1969; Herzberg &« Herzberg, 1962), with 
up to 100 eggs at a time, allow quick establishment of a breeding 
colony. Basinger (1931) estimated for California that each individ- 
ual snail is able to lay 430 eggs during 8 months when oviposition 
is possible. Fromming (1954) observed in his aquarium 40-50 eggs 
each brood and four broods in the course of 7 months. 
Mention should be made of a very well developed homing instinct 
which makes Helix aspersa return regularly to the same favourite re- 
treat each morning after its nightly foray (Duncan, 1943). Taylor 
(1910) relates an early marking experiment conducted in England in 
1884 which demonstrated that H. aspersa "has frequently been ob- 
served to traverse with much labour, broad dusty roads, and climb 
rough walls to reach some favorite food, but instead of secreting 
itself at daybreak, near by, will retrace its toilsome journey morn- 
ing after morning to its retreat." This same homing behaviour has 
been described and studied for Helix pomatia in Sweden by Edelstam 
& Palmer (1950). They found that, if removed beyond the possible 
limit of homing, the snails would respond to available stimuli rath- 
er than spread by chance over surrounding favourable areas. "Regard- 
ing the evolutionary value of a habit like this one - we essentially 
agree with a verbal suggestion made to us by Prof. Bernhard Rensch 
that, on the average, an organism with little ecological plasticity 
will always have a greater chance of survival in the area where it 
has already persisted for some time with success. However, this in- 
stinct is bought at the price of a poor spreading capacity. That 
this is essentially so in H. pomatia is shown by its distribution 
in Sweden where it still occurs only in those limited areas where 
it has been planted out by man, even if interjacent areas provide a 
favourable habitat to the species." 

(Extracted from "Helix aspersa, portrait of a colonizer" by Z. Bar, 
LEVANTINA 2: 9ff. (May 1976), a malacological newsletter published 
jointly by the Israel Malacological Society and the Municipal Mu- 
Seum, Nahariya. Compiler: Henk K. Mienis, Kibbutz Netzer Sereni, 
70 395, Israel.) 
