I DELIGHT in watching the habits of fish, insects, &c. in a good Aquarium. We are indebted to these inventions of more modern times for some curious discoveries in natural history, especially those which refer to the hitherto unknown habits of marine animals. Let me here mention one instance of a peculiar instinct in a small crab, which may interest the reader, and which afforded me much pleasure, especially as I believe the facts I am about to relate are not generally known, or if known, only to a very few persons, and those few not of the scientific world.
At the same time, I am unwilling to claim any credit for the discovery. It was first communicated to me through an amiable clergyman and his wife residing in Scotland, who, having an aquarium, and living close to the sea, had frequent opportunities of ascertaining the facts I am about to relate, and which I was able myself to verify during a recent sojourn I made at Bognor in Sussex.
The facts are these.There is a very small species of crab, called by the fishermen at Bognor the spider-crab, and which has its body and claws covered with numerous very minute hooks, scarcely perceptible to the naked eye, but perfectly so with the help of a magnifying-glass. It may be asked, “What can be the use of these hooks?” You shall hear.
This crab is a prodigious coxcomb, and very careful of its own precious person. Either then for the purpose of concealing itself from its enemies, or from an innate love of finery, it selects a quantity of seaweed, always preferring the most gaudy colours, those chiefly red. Having selected them, he cuts them into fine thread-like slips, and runs them through the hooks. When he has completed his toilette, he appears one mass of seaweed, thus not only disguising himself from those enemies which might otherwise make him their prey, but perhaps feeling himself the best dressed crab in the neighbourhood.
It is also remarkable that this labour for making his toilette is renewed every morning, so that the quantity of seaweed consumed is very great. This may be observed by anyone who has the opportunity of keeping these comical little crabs in an aquarium, although I regret to add, that they do not live long in a state of confinement.
They are caught in considerable numbers in the lobster and prawn baskets at Bognor, together with another crab, about the same size as the spider-crab, but which is not furnished with hooks. On speaking to the Bognor fishermen respecting the latter, I found they all entertained the idea that the seaweed grew on them.
The thread-like weeds may, however, be drawn, out of the hooks one by one until the little dandy is left perfectly bare. I am not aware in what other localities this crab is to be found beyond those I have mentioned. I could not hear of it either at Brighton or Eastbourne, but I hope that this notice may induce others to prosecute some inquiry into the habits of this singular little animal.