CRUSTACEA.
The Struggle for Existence among Hermit Crabs.—It is well known that the Hermit Crabs (Paguridæ) have occasionally royal battles for the possession of some old empty shell which serves them for a temporary lodging, and the following account is of a proceeding which I one day witnessed on the Hastings beach. I had been hunting for Hydroids at low-tide, and just as I was leaving I noticed a mob of Hermit Crabs. In warm weather these are usually plentiful enough, but it struck me that on this occasion they were collected together for some purpose. In fact, so preoccupied were they, that they did not pay any attention to me, though I was stooping over them. The Crabs were of different sizes and in various shells—Purpura, Natica, Whelk, &c. One which occupied a Purpura was rather a little fellow, and ensconced behind the thickened mouth of the shell he looked very snug and secure. He was evidently the central figure of the group, and was endeavouring to edge away from those around him. At length up stalked a big burly fellow, and seized him by the front leg at the joint. Then commenced a series of smart tugs, perhaps half a dozen, and then a slight pause, after which the tugging commenced again. This kind of thing continued I suppose for ten minutes, and if only fair means had been used no doubt the assailant would have had to desist, but it seemed to strike the intelligence of one of the bystanders that in rendering assistance he might also serve his own ends; so, coming forward and going behind the Purpura shell, he seized hold of it. Then began again the tugging by the original offender. This continued for some time, but even with this assistance no impression seemed to have been made upon the little fellow in the deadly grip of his antagonist, for he remained almost out of sight, and firm as a rock. Then another volunteer stepped out of his own accord and seized hold of the shell of No. 1 assistant. There were thus two Hermit Crabs resisting the pull of the original assailant. No sooner had the second assailant lent a hand than the victim was instantly "whipped out" of his shell like a cork from a bottle! and directly the little fellow had been extracted from his shell No. 1 assistant slipped quickly out of his domicile and scrambled into the empty Purpura, thus ousting entirely the original aggressor, and made off with his ill-gotten property.
It would appear, on considering the above, that the Hermit Crabs must have very decided preference for certain shells; for, considering that all the other parties concerned were properly domiciled, why should they have so coveted this particular shell? In this case, if I remember rightly, the shells of the aggressors were Naticas, that is to say, shells with wide open mouths, and not likely to afford anything like the protection that a Purpura would offer with its greatly thickened and dentated lip, and a stout shell into the bargain.—P. Rufford (The Croft, Hastings).
