Last Leaves from Dunk Island, by E. J. Banfield

The Reef Mantis

Low tides occur during July, August and September, and lay bare to the sun considerable areas of the reefs within the Barrier, which at the opposing period are revealed only to the gleams of the moon. Then is it wise to make opportunity and, equipped with a fish-spear and a canister to contain delicate specimens of marine fauna, use the two hours of the afternoon in pursuit of novelties. In the degenerate condition of the corals of the shallows in the vicinity of this island it is also wise to restrain expectations, for the marvels of fertile reefs, though represented, are not common. In the flurry of the receding tide, however, all sorts of strange creatures are heaped, and, taking refuge under blocks of dead coral and in isolated pools, may be accepted as typical of the fauna secure from scrutiny on the deep-water reefs.

Lately three or four species of what are known as mantis-shrimps have been found and sent to one or other of the museums. These crustaceans have a range extending throughout the warm waters of the Pacific, but being of necessity shy and secretive — for they have many enemies — are not often seen, at least in these parts, where time for investigation is limited. It is found on inquiry that others who have a much wider range know little or nothing of a most interesting animal. As the familiar name implies, the mantis-shrimp has a feature in common with a popular insect — the praying mantis, flycatcher and voracious feeder, which has been known to seize and eat a small frog.

One of the specimens submitted to the Australian Museum at Sydney is thus described by an expert on the staff:

“The specimen presented is most acceptable, since it is new to the museum collection. It is a representative of a group of mantis-shrimps, the members of which possess peculiar claw appendages in which the last segment shuts down like the blade of a pocket-knife. These claws form very efficient weapons, and it is because of their position that the resemblance to the common praying mantis gives them the popular name applied to the insect. Mantis-shrimps are generally found in shallow water, burrowing in the sand or hiding in the crevices in rocks and corals. They are described as lying in wait at the mouths of their burrows, darting out on fish and other animals, which are seized with their great claws, and retreating with great rapidity to the bottom of the burrow with their prey. They have a long series of larval stages, and the larvae are all distinguished by the large size of the carapace (the shield covering the back) which in some cases envelops the greater portion of the body. In the warm seas some larvae attain a relatively large size, sometimes exceeding two inches in length, and the glass-like, transparency gives them a striking appearance. During the larval stages they swim at the surface, and the influences of the ocean currents account for their wide distribution.”

Differences in size, appearance and colouring are noticeable among the representatives of the family, even in a limited area. One, the most formidable, attains a length of ten inches. It is a weak, almost broken-backed creature, with a most resentful and sudden temper. Although its wonderful weapon has been frequently found on the beach, only one living specimen has been secured, for its habits appear to be nocturnal. The burrow is in the centre of a low, flat-topped mound in unctuous mud fortified with sand, and generally its inhabitant is not at home. One came up on the bait of a fishing-line at night, and presented such a dazzling effect, as it was lifted into the boat, absorbed with its prey, that it was handled rashly. With lightning-like rapidity it struck, and the biggest and sharpest tooth of its scythe pierced the tip of my finger. The deed was so sudden that, although the blow was felt, there was no immediate pain, but blood flowed as from a far bigger wound.

The weapon resembles a scythe in shape, but is unlike that implement in that it is fitted with a series of comb-like teeth, exceedingly sharp and graduated in length. At first glance the limb supporting it appears to be malformed, for it bulges at the elbow joint into a “dumb-bell,” weighty compared with the size of the animal. The purpose of this development is obvious. Does it not correspond to the biceps of human beings, putting wonderful force into the blow? The creature, trained by nature to defend its life and secure its prey, uses its weapon with precision and skill. It kills and at the same time clutches.

One of the family, developing along different lines, is even better of its hands; remarkable to tell, it carries a cestus of hardened shell as a means of protection and enforcing its rights. From the structure of the limbs it is safe to assume that neither of the species delivers a forward, but rather a descending, hammer-like blow, and the mimic pugilist’s design is, no doubt, exactly the same as that of the prize-fighter. The twinkling blow stuns the victim, which probably never has time to come to. As far as local knowledge goes at present, the boxer is found in these waters only in a small form, which can deliver but a feeble, almost affectionate tap; but it seems that its “dumb-bell” elbow joint is bigger relatively than that of its cousin with the slender-toothed scythe. Some one has said that nature seems everywhere in advance of those inventions of which we, as men, are so proud. The mantis-shrimps, afford two examples of the truth of the saying.

In that fine book, A NATURALIST IN BORNEO, the late Robert W. C. Shelford describes a giant of the boxer kind, which when dropped into a glass tube full of spirit shattered it with a blow. He concludes a detailed description of the animal thus:—“The action is as rapid as that of a strong spring, and the force of the blow has to be felt to be appreciated; I am quite certain that it is sufficient to stun any small fish or crustacean. It is conceivable that a stunned animal could be held and quietly devoured.”

No available reference to the mantis-shrimps mentions a most attractive feature, the lovely and fanciful colouring. Some are honey-yellow, some moss-green, some drab, some decked out with all sorts of fringes and finery in delicate and living tints. In the sunlight the hues change and sparkle with intensity. No jewel polished by the skill of man flashes forth more vivid and more varied splendour. Nor is any human acrobat more supple or more agile, as an incident connected with the preservation of a specimen for expert examination demonstrated.

Dropped into limpid fluid in a tube so narrow that reversal seemed impossible, one of the lovely creatures performed a series of somersaults with rapidity bewildering to sight. For a few seconds the tube seemed to contain an agitated tumbling mosaic, compact of all the gems of the world. Was ever a fight for life so fierce and so futile? Was ever a death scene so gorgeous? It was glorious. It was shocking. From such another spectacle of death-agony and brilliancy may the fates protect us! Unlike the powerful representative of the family in Borneo, it was unable to shatter its prison walls. There was no possible escape in the circumstances, and deliverance would have been but added cruelty. When, at last, it was still, upright in the transparent cell, its fore-limbs in the posture of supplication, it was not a museum specimen, but an unspeakably pathetic object appealing for a vow of abstinence from all investigations involving the sacrifice of life. Worth such a gallant struggle, its little life seemed too precious to waste deliberately, even in the cause of science — and be sure, had not the experience been exceptional, some drowsy drug would have eased its pangs. The lesson of that scene, illuminated in tints unstainable, unfading, will live as long as memory.

In some countries blessed by the living waters of the Pacific certain species of mantis-shrimps are eaten by the natives, six making a good meal. Here they do not appear to be plentiful enough to afford a change of diet. Besides, whose is the haughty stomach that demands a meal of delicate jewellery? Better perhaps to souse them in formalin, after a preparatory whiff of chloroform, for the edification of the learned folks of the museum.

Last updated Sunday, March 27, 2016 at 11:50