CAVE OF LIVING LIGHTS

New Zealand Herald, Volume LXXIV, Issue 22628, 16 January 1937, Page 10 (Supplement)

CAVE OF LIVING LIGHTS

By R. A. FALLA, M.A.

The Wonders of Waitomo's Unique Tourist Attraction IN the formation nf the varied scenic attractions that New Zealand offers to the tourist natural forces on a large scale have played a major part. Incalculable masses of ice have carved the southern region of sounds and lakes and heat and molten rock have produced the notable volcanic and thermal regions of the north. Luxuriant plant growth adds peculiar charm to scenery of many forms, and here and there indigenous bird life adds a memorable touch of movement and song. Fascination and Charm Tributes expressed by visitors as to the awe, fascination, and charm of all these features have been many, but it is surprising what a large number have selected for special mention a feature to which the chief contributor is an insect. "I consider this glow-worm cave of Waitomo to be one of thc sights of the world, and of great interest to scientists as well as to ordinary people," said Viscount Burnham. of the Kinpire Press Delegation in I!)2.*>, and he is not alone in the expression of such an opinion. A considerable crop of literature has already boon inspired by this cave, and only this year a lucid and readable account by Dr. W. Rnshton Parker, an octogenarian traveller, has appeared in Knglish papers.

Delicacy ol Description Those who have already seen the care and tlio.se who have still to do so will alike appreciate the delicacy of description contained in the diary of Mr. C. L. Edwards relating to a visit in May, 192;}: —"After due admonitions, and obeying the order to leave nil lamps

behind, we stepped cautiously in single tile down, down to a lower level. Collecting ourselves at an unseen bottom, we held each one his breath, and listened. To each in turn a whisper floated, 'Get into the boat' . . . Then, gradually we became aware that a vision was silently breaking 011 us. Either we were moving (though without oars) or a panorama was passing before us. I recollect just noticing the glint of a wire which might have been fastened along the wall of the cave, and on which our dumb boatman might lie pulling. But, at any rate, a radiance became manifest which absorbed the whole faculty of observation—the radiance of such a massed body of glowworms as cannot be found anywhere else in the world, utterly incalculable as to numbers and merging their individual lights in a nirvana of pure sheen.

Mystic Light "And now as to the disposition of this mystic light, which produced itself all unaided, in innumerable points. The cave was evidently similar in structure to all the others, giving an endless variety of outline; but " whatever was there became dotted over with points of golden light as closely studded as the letters on a printed page, a truer parallel than the glibly quoted starry sky It did strike me, however, that the higher reaches of the cave resembled the Milky Way. But from those heavens stretched down wondrous stalactites all clothed in living light, and appearing like arms ready to lift one right up to those faraway stars; and not only above the main silent river, along which our noiseless way as truly a gliding, but in branching fjords surprise burst, on us again and again, revealing fascinating vistas of the same glowing and shapely splendour. To bow the head in adoration of Beauty was but to meet its whole shimmer reflected, unwrinkled, in the quiet river below."

Life History of Insect In building up an explanation of the cause of the phenomenon thus vividly described, much patient research has been undertaken by local entomologists, notably by Mr. G. V. Hudson and Mr. A. li. Tonnoir. There is no excuse for the appearance of loose and inaccurate.

Specially Written for the New Zealand Herald

popular accounts of the insect for its life history has been carefully worked out by observation and experiment. 'J lie "glow-worm" is the larval stage of u fungus-gnat v.liich is quite distinct from, although related to, both the mosquito and the crane-fly or daddy-long-legs. The family oflungus-gnats is well represented in New Zealand, 225 species having bee/i listed, but Aracbocumpa luminosa outshines all the rest. It may be found on moist rock faces and damp crevices in many shady places, but a combination of favourable circumstances makes the cave at Wailoino unique us a home for the insect and a spectacle for the tourist. Hanging in Darkness As in the case of most insects the larval stage is the most active feeding stage in the life history. Lach "glowworm" is a cylindrical, segmented, semi-transparent creature about 1•} inches long. during its growth produced a tubular jelly-like sac which js attached to the rock, the larva remains within this shelter and spins a number of further small threads which hang vertically down for a foot or more. 'I ho whole "much, being sticky, would he a formidable snare in daylight, but it is doubly so when it hangs jn darkness surmounted by an alluring point of light. The prey thus easily caught con 1 - sists.of small midges which have passed their own egg, larval, and pupal stages in the mud-hanks of the underground stream; there are enough of them evidently to feed the myriads of glowworins and still perpetuate the healthy swarms of successive generations. A midge coming into contact with one of the banging threads is immediately entangled and then drawn up to the waiting mouth of the fungus-gnat larva; the whole process so reminiscent ol the ways of spiders that it led to the bestowal of the name Arachocampa, the "spidergrub." When fully fed the larva is transformed into a quiescent fasting pupa and a few days later into the long-legged gnat about twice the size of a mosquito. This perfect insect is

rarely seen or caught, as it shuns daylight until the work of depositing the eggs is finished, after which the gnat dies.

Specialised Organs This life-history may be observed in many shaded and moist places, but except in limestone caves the snare threads are comparatively short. The production of the light is an interesting phenomenon and the study of it is linked up with the investigation of lieatless living light in many organisms found 011 land and in the sea. In the case of the glow-worm it is the product of specialised organs situated in the tail segments of the larva's body. Their actual structure is comparatively simple, an outer layer producing the light and an inner layer reflecting it. Urate crystals in these inner cells act as a barrier to the internal dispersion of the light and its full power is thus directed outwards. By means of the various tests used to determine the efficiency of light this organically produced luminosity is found to be amazingly efficient—97 per cent more so than incandescent gas, 90 per cent greater than the oljctric arc. and 65 per cent greater than sunlight. Should the secret of such a process ever yield to scientific inquiry our modern lighting methods could be discarded as obsolete and wasteful. Reflex Control In the glow-worm, as in most luminous animals, the process seems to be under some form of reflex control, and the lights may disappear in response to unfamiliar vibration. It is for this reason that silence is enjoined at Wuitonio and the visitor compelled to keep his possible exclamations temporarily suppressed. Many no doubt have been tempted to test the theory, or have suspected, with that incorrigible humorist . P. Herbert, that the need for silence is psychological rather than biological. It is probable that in a continuous buzz of noise the glow-worms would gradually light up again, for animal reflexes do not respond indefinitely. Intermittent noises, however, would always cause some of the lights to disappear, and it may be concluded that from every point of view the rule of silence is a good one.