Shells appear to be used occasionally by other species besides man. Oyster-catchers at breeding time prepare a number of imitation nests in the gravel on the spit of land where they build, putting bits of white shell in them to represent eggs.[213] This looks like a trick in order to conceal the position of the true nest. According to Nordenskjöld, when the eider duck of Spitzbergen has only one or two eggs in its nest, it places a shell of _Buccinum glaciale_ beside them. The appropriation of old shells by hermit-crabs is a familiar sight all over the world. Perhaps it is most striking in the tropics, where it is really startling, at first experience, to meet--as I have done--a large _Cassis_ or _Turbo_, walking about in a wood or on a hill side at considerable distances from the sea. A Gephyrean (_Phascolion strombi_) habitually establishes itself in the discarded shells of marine Mollusca. Certain Hymenoptera make use of dead shells of _Helix hortensis_ in which they build their cells.[214] Magnus believes that in times when heavy rains prevail, and the usual insects do not venture out, certain flowers are fertilised by snails and slugs crawling over them, _e.g._ _Leucanthemum vulgare_ by _Limax laevis_.[215] =Mollusca as Food for Man.=--Probably there are few countries in the world in which less use is made of the Mollusca as a form of food than in our own. There are scarcely ten native species which can be said to be at all commonly employed for this purpose. Neighbouring countries show us an example in this respect. The French, Italians, and Spanish eat _Natica_, _Turbo_, _Triton_, and _Murex_, and, among bivalves, _Donax_, _Venus_, _Lithodomus_, _Pholas_, _Tapes_, and _Cardita_, as well as the smaller Cephalopoda. Under the general designation of _clam_ the Americans eat _Venus mercenaria_, _Mya arenaria_, and _Mactra solidissima_. In the Suez markets are exposed for sale _Strombus_ and _Melongena_, _Avicula_ and _Cytherea_. At Panama _Donax_ and _Solen_ are delicacies, while the natives also eat the great _Murex_ and _Pyrula_, and even the huge _Arca grandis_, which lives embedded in the liquid river mud. The common littoral bivalves seem to be eaten in nearly all countries except our own, and it is therefore needless to enumerate them. The Gasteropoda, whose habits are scarcely so cleanly, seem to require a bolder spirit and less delicate palate to venture on their consumption.