The Atoll of Funafuti, Ellice group : its zoology, botany, ethnology and general structure based on collections made by Charles Hedley of the Australian Museum, Sydney, N.S.W.
[VI.] — The Crustacea
The Collection consists of over three hundred specimens, representing sixty-two species, live of which are herein described as new. The various tribes are represented as follows:—
The species regarded as new have been described as fully as possible, and include one each of Pilumnus, Diogenes, Porcellana, Betceus, and a very interesting Epicarid of the genus Athelgioe, which was found on a Hermit Crab—Aniculus typicus.
I have also added such notes as would tend to aid in the identification of some of the lesser known species, and of any variations or departures from the typical forms. Among the rarer species noticed may be mentioned Xanthodes nitidulus, Dana; Carpilodes margaritatus, M. Edw.; Actaeodes speciosa, Dana; Pseudoozius caystrus, Ads. & White Tetralia cavimana, Heller; Geograpsus crinipes, Dana; Harpilius miersii, De Mann; Giro-lana latistylis, Dana, and Lithotrya nicobarica, Reinhardt.
The Geograpsus crinipes appears to be a strictly terrestrial form, breathing air direct by means of the hair-lined pores situated between the bases of the third and fourth pairs of legs, as in the genus Ocypoda. As far as I can ascertain, this is the first instance of a Grapsoid Crab living wholly on dry land.
Mr. C. Hedley has kindly supplied the following field notes on the Crustacea:—
"The dominent note in the life of a coral atoll, as expressed by the Funafuti fauna, struck me as the abundance and ubiquity of Crustacea. The Avifauna were but sea fowl, the indigenous Mammalia but rats, the Reptilia only a stray scink and gecko, page 128while insects and land mollusca, usually so profuse in tropical latitudes, were barely represented. Into the vacant places swarmed Crustacea. Not an inch of the atoll world is secure from them. The Ccenobita wander across from shore to shore and dispute any stray edibles with the rats. Some crabs even take up their residence in the tree tops of Pandanus, while, as everybody knows, Birgus is as much at home on a palm bole as a squirrel on an oak. As I believe, and have endeavoured to demonstrate (pp. 22, 23, ante), that the coconut is foreign to the native flora, and of comparatively recent introduction from abroad, it follows that the taste for this nut has been acquired in historical times by Birgus, whose original food was probably Pandanus fruit.
" Human habitations are not even secure from crabs. Often while quietly reading or writing, especially at night, have I seen crabs, for instance Ocypoda ceratophthalma, steal warily across the floor towards some attractive food. Deterred for the moment by a missile or an exclamation, they would recommence like any impertinent mouse their pertinaceous efforts when attention lulled. One impudent intruder established himself in a burrow under my very bunk.
"Active as they are during the day, it is at night that the land crabs hold high carnival. A traveller has thus described his experience of his first night on an atoll*:—' It was fortunate that we had provided ourselves with lights, or we might have imagined our habitation to be occupied by every noxious reptile. As far as the fading daylight had shown us, the Island appeared covered with rough pebbles of coral. Imagine our surprise on lying down to sleep, to find that all these imaginary pebbles had become endowed with animation. A dull crackling, or rather rustling, noise seemed to pervade the air, earth and sea, and so disagreeably near to us, that I started up to ascertain the cause. Judge of my astonishment, when I perceived the numerous rough looking pebbles all alive, moving about briskly upon the floor of our hut, and crawling over our mats in all directions. A little nearer inspection discovered them to be shells of a species of perrywinkle of all sizes, each being occupied by a kind of hermit crab, projecting his rough and ugly looking claws from the orifice of the shell. I went outside, and found the entire surface of the Island in motion. The moon enabled us to see that not only on the ground, but even on the trunks of the trees, on the roofs of the huts, and every place to which their claws could gain access, there were these creatures to be found.'
" On the beaches the Crustacea were everywhere abundant, particular species possessing each their special zone. About high tide mark on the windward shore promenaded Grapsus maculatus, page 129a crowd of which scattered before the footsteps of a visitor, and sought refuge under loose coral blocks or in deep pools. Rolling over a slab of dead coral rock anywhere between tide marks exposed the haunt of a little community of Petrolisthes dentata and Leiolophus planissimus. Intercepted in their efforts to escape, these would flatten themselves down to the surface of the stone so closely that the collector's fingers with difficulty grasped them. The deeper rock-pools at the border of the reef-flat, the chief home of Salarius, were usually tenanted by a few Calcinus elegans, whose brilliant red, blue, and white claws distinguished it as the dandy of the company. This species is never found out of the range of rough waves. The extreme windward portion of the reef left dry at low tide was but rarely attainable Aniculus, whose bristly claws usually protruded from a stolen Turbo shell, was a distinctive feature of this zone. In the honey-combed pits of the nullipore mounds that breasted the surf, cowered Daira perlata. The close resemblance of colour and contour to the surrounding rock, rendered this crab difficult to detect, and when seen the creature's powers of adherence and the sweep of the Pacific rollers rendered it as difficult to seize.
" The mangrove swamp was very barren of Crustacea compared to the usual population of such places. One quite missed the droll little Gelasmus, waving his big claw in defiance. After gathering coconuts, the natives usually husk them on the spot and throw the discarded husks in a pile to decay. These stacks of rotting husks are prolific collecting grounds for Invertebrata in general, and the favourite shelter in day time for Birgus and Cardisoma, the latter of which also burrowed in soft muddy places."
* Webster—Last Cruise of the "Wanderer," n.d., p. 55.