IN TOUCH WITH NATURE

Otago Witness, Issue 3764, 4 May 1926, Page 9

IN TOUCH WITH NATURE

lr. THE GLOW-WORM. By J. DRUMMOND. F.L.S.. F.Z.B. New Zealanders who contemplate exploring the magic realms of insects in this Dominion will find a guide in methods followed by Mr G. V. Hudson. There is still a fairly general opinion that an entomologist—bug hunter is a commoner title—is an eccentric person, be-spectacled, careless in dress, absent-minded, and not quite normal, but this fantastic person is fading away. The public is beginning to realise that entomology is as serious as it is absorbing. In the war of supremacy, in which men must stand against hosts of enemies, it is highly important. Those ( who take it in hand may find it not only a pastime, but also an occupation by which htey can add to knowledge and make the World better and safer for their race. Some entomologists collect any and all insects. In these days of specialisation most entomologists who take their work seriouly study only a particular order This may be the moths and butterflies, the mosquitoes and gnats, the great beetles the dragon-flies, the flies, the bees an I wasps, and so on. Mr Hudson, while giving most of his attention to New Zealand’s moths and butterflies, has failed to resist the temptation to wander in the paths of other insects. In this way, he was lured amongst the glow-worms. He made the first effort to study them in New Zealand. He began some 40 years ago. His interest in them is as deep as ever. He has become acquainted with them In their own homes and in homes he provided for them. He has discovered some of their methods, has wntelied- them as they go about their everyday affairs, and has obtained some knowledge of their lifehistory. All this, probably, has served to show him how much relating to them remains to be disclosed. Early in 1885 Mr Hudson, who lives at Karori, Wellington, found in the Wellington Botanical Gardens several glow-worms. In the following year, he went more carefully into the inquiry, keeping some of the insects in captivity. He noted that the light did not shine regularly. It was brightest sometimes at night, sometimes in the early morning. In later years h° has found that the most brilliant display in the natural habitats is on dark, damp nights, whch a light nortli-west wind Is blowing. In 1886 one of his captive "Jowworms disappeared. He assumed that it had buried itself in the to undergo its transformation into a chrysalis, on life’s journey to the culminating stage of perfoet insecthood. In about a month his opinion was supported by the emergence of a perfeqj: insect. This proved to be a fly, but ' not the species into which the glow-worm develops. In 1888, walking up the bed of a stream in the Botanical Gardens at night, with a bull’s-eye lantern, he caught more glowworms. As soon as he saw the light shine out he inserted a thin stick behind the glow-worm, which adhered to the stick and was carried to Mr Hudson’s home In a tin box, with damp moss. A further supply was placed in a large bell-glass with, stones and ferns, and with about an Inch of water, the nearest he could get to the glow-worm’s natural habitat. On the morning of April- 4, 1889, he was delighted to see a fly standing beside the akin of a glow-worm chrysalis, from which it had emerged. Experts in Australia and Germany expressed an opinion that the fly had not come from a glow-worm. Determined to set the insect’s identity at rest, Mr Hudson caught more glow-worms and kept them in captivity. All of then* died In 1890, after spending three hours in the bed of the stream, ho caught about twenty glow-worms. Two were transformed into chrysalis. One died in that stage. From the other there emerged a fly that exactly resembled the one he had seen near the chrysalis skin the previous year.

The emergence of that fly was noted by Mr Hudson very carefully. On examining the chrysalis at 8 a.m., he saw that it had become very much paler than usual. At 2 p.m. he saw the fly perched on the chrysalis, with its head down towards the tail of the chrysalis, and with the extremity of the fly’s abdomen still in the chrysalis skin. The fly remained in that position until 5 p.m the following day He then removed it to a large glass-topped pill-box on the table in the sitting-room. Returning at 7 p.m. without a lamp, he was astonished to see the inside of the pillbox brilliantly lighted. A strong light came from the extremity of the fly’s abdomen ; it was about half as bright as the light emitted by a full-grown glow-worm grub. The phenomena relating to the emergence of the fly from the chrysalis, and the fly’s subsequent luminosity, were observed also by Mr Hudson’s brother. As the fly was a female, Mr Hudson took it into the big ravine, to see if it would attract males. As soon as he placed the box in the bed of the stream, the fly again lighted up, strongly illuminating the inside of the box. Thirty-five later, when Mr Hudson re-visited the box, no other insects had arrived. He left the fly to send out its light for ten more minutes, but with the same result. The glow-worms usually seen are the insects in their grub stage, the larvae in entomological language. The light, evidently, is emitted in both the grub stage and the perfect stage, but not in the intermediate stage, when the insect is a dormant chrysalis ; a pupa, entomologically. The grub weaves for itself a web, like the web of a spider. Mr A. Norris, a pupil of Mr Hudson, has seen grubs in their haunts actually weaving. The web is a kind of mucus discharged from all parts of the grub’s body. A grub,’ when making a new web, raises its head and part of its body into the air, and reaches around until it strikes something. By drawing its head back slightly, it makes a very fine thread of mucus. By gliding motions of its body and by movements of its head, it makes pendant strings of beads. Some of these are from on© inch to four or five inches long. When a grub is shining at night, the reflection of the light may be seen alolfg the main thread or tube. The grub’s lamp is at the end of its body. It is semi-transparent, and there is great diversity of form in it. The grub can withdraw or extend it at will, but the grub may cease shining immediately without withdrawing the lamp. Mr Hudson has found that grubs cease to shine on very cold nights, in the daytime, and in a room lighted artificially. Only one species of glow-worm is known in New Zealand. It is a fly. Arachnocampa luroinosa, which means the luminous creature that makes o web like a spider’s. The syndics of the Cambridge University Press have sent a copy of a valuable work entitled “Monocotyledons,” a study by an English botanist, Dr Agnes Arber. Both Dr Agnes Arber and her husband. Dr E. A. Newell Arber, have worked in botany Dr Newell Arber. who died about nine years ago, was demonstrator in nalsepn tology at Cambridge University. His important work was amongst fossil plants Some of the best of it was put into a memoir on New Zealand plants of the Mesozoic Era, the era of Middlo Life This labour of love, published ns a bulletin by the New Zealand Geological Survey, is so complete that it places the Mesozoic botany of New Zealand on a sound basis ft is a notable contribution to this Dominion’s scientific literature. • Dr Agnes Arber’s “Monocotyledons” is a study of the morphology of one of the two classes of the Angiosnerms. These are the dominant plants on the earth's surface. There are more than 13,000 species of them. Wherever plant life is possible they grow. Some cover the surface of a pond, others yield- most of the food crops for men, cattle, sheep, and horses, others beautify landscapes and gardens. The bright flowers of many of them give boundless, pleasure to every human being. They re not only the most ornamental productions of Nature, but also the highest c. resale a

of evolution in plant life. They are divided into two di. -inct divisions. The plants in one of these divisions, the Dycotlyedonr, have each two seed-leaves, the plants in the other division, the Monocotyledons, have each one seed-leaf. Dr Agnes Arber’s study relates to the form, the structure, and the external apnearance of the Monocotyledons—that is, to their morphology. She describes and illustrates them minutely and delicately, and discusses theories, hvnotheses, and doctrines on which they have a bearing. Her book leaves readers impressed with the profound obscurity in which the origin of plants is wrapped. The search for the origin of plants has proved as elusive •** the quest for the Holy /rail- In obscurity qu!^r~r a i m P e P etra ble is the force that impels plants in !i U4,r evolutionary progress. Dr — views the evolution of plants as - iourney along lines that are fore-ordained: but the impelling force is a myster of mysteries to her: “The secret of the great underlying principle that determines these lines of progress is hidden from us. Morphological study has revealed something, and, we hope, will in future reveal more, of the .laws according to which it works, but, try as we may, we have never succeeded in lifting as much as a corner of the veil that hides the mystery itself. I doubt whether we can better the conception, foreshadowed nearly a century ago, that not only the eternal harmony stars and the changing phases of the inorganic world, but even the course of the stream of life in its passage down the ages were determined once and for ever, when the reign of law in the Dawn of All Things.”