IN TOUCH WITH NATURE

Otago Daily Times, Issue 20291, 27 December 1927, Page 2

IN TOUCH WITH NATURE

HISTORY OF A NYMPH. By J. Drummond, F.L.S., F.Z.S. A «iii"iilar!v uglv insect sent by Airs r 11. Wallers, Torch,ape, Kaihore, 82 miles -.out li-ea,-i, of Auckland city, has no resemblance to graceful, elegant dragonflies. To compare it to one of the semi-divine maidens that danced attendance on superior gods and goddesses, and lived in rivers, fountains, and forests, would be absurd. Yet it is a nymph of the largest, handsomest, and most conspicuous dragonfly in New Zealand, Uropetala carovei, dist languished by bright golden spots on its long, black body. The ugly nymph, about , an inch and a-quarter long, brown in 1 colour, wingless, with a black cap on its . head, is in an early stage of inseothood. j Mrs Walters found her nymph on nand ( towels on the floor of her washhouse. , The place is an unusual one. A burrow in | swampy soil is this creature’s home. It ] feeds furiously on small insects, which it < catches by a peculiar structure, like a ] mask, fixed by a hinge tp the lower part 6 of its head. The mask is a development ] of the Ipwer lip. When not m use it ( can be tucked close under the head. It ] ends in two curved hooks. Creeping softly e towards its prey, the nymph suddenly ex- t tends the mask to full length, secures the ( victim with the hooks, and holds it close against the jaws during the meal. A dragonfly nymph hatches from an egg. When ready to break its prison . walls it occupies the shell from end to end ] except for a. small space in front of the - head. its tail end is bout beneath its i body. For some days before escape it , may be seen through a microscope, making slight movements. The first sign that it is about to enter into a wider life is the cracking of the shell in front of the head. The crack runs round the shell. From the crack there comes out slowly a very thin mciubranco Idled with fluid. The membrane continues to expand. The nvmph’s head begins to bulge into it. Very slowly, the head occupies the whole of the membraneous vessel. The membrane bursts suddenly, and the nymph, wriggling violently, flows out of its shell. This remarkable process has been observed in nymphs of English Probably it is the same in New Zealand’s mem- 1 hers of the group. In one case in England the nymph that emerged from the egg, which was only oue-twentieth of an inch long, was a helpless cripple, the same size as the egg, lying on its side. In two minutes it began to wriggle. The skin split along its back, and there came out into the , world a perfect dragonfly nymph, which immediately straightened its legs and ar- , ranged its mouth-parts. Stages in the ] life of a dragonfly nymph are marked by moults, in which the outer skin is cast. The skin, composed of horny mate- , rial, may be greatly stretched when new, , but less so as the nymph grows. The skin , becomes too small for the body. Feeling that its clothes are too tight, the nymph makes a new garment outside the old i one. The new one, when complete, cuts i off the sup of nourishment from the old one. A line of weakness develops ■ along the back of the old one. The i nymph, working its tail end forwards in- i side the old coat, forces its back through a rent along the line of weakness. It r humps its back through the rent, with- 1 draws lirst its head and then its legs, i walks out of lh e old shell and the moult i is complete. t c Most species of insects have a stage *■ of complete rest in life’s track. Dragon- 1 flics are active continuously. In hug- 1 land, probably in New Zealand also, a $ dragonfly nymph, when it feels that it is i approaching the highest stage, crawls up 1 a support. Slight wriggling movements 6 of its body are followed by a rent in the skin down the middle of its back. The j insect emerges, clears its crumpled wings 1 from their sheathing-pads, makes a quick v movement and leaves behind the e nymphal stage, to become a very per- 7 feet insect. In Tennyson’s words, an inner e impulse rends the veil of its old husk; it f dries its wings, like gauze they grow; r through crofts and pastures wet with dew J a living flash of light it flies. Entomologists are discarding the use of the word nymph for a stage in the lives of dragonflies and of some other insects. There ? may be curiosity as to the origin of this c word’s application in a sense that seems * to have no meaning. They are called ) nymphs, a naturalist who wrote 180 years ago explains, “in allusion to brides, bo- £ cause, when they leave the nymphal state *■ they often are arrayed in gaiety and c splendour.” ' ' t As Dr R. J, TiJlyard, chief biologist at tho Cawthron Institute, Nelson, is the j hjghost authority in the world on dragon flies, ho was interested in these insects at the Cass, a tussocky hill district in the E heart of tho Southern Alps on the lino of 5 the Christchurch-Grey mouth railway. In- ! spccting a small mountain stream there, he ; found many burrows made by dragonflies J nymphs in peaty soil Inserting his finger E into some of the burrows and working tiis c hand down to a depth of lOin or 12in, ho felt the nymphs and pulled them out. They f were very inert, and could be handled witn i safety. Adult dragonflies he saw there and t at Arthur’s Pass are slightly different from \ Uropetala carovei, end he dedicated tho i species he saw to Dr C. Chilton, with tho i title Uropetala Chdtoni. As far as is g known, this kind has not been found in any other parts o[ New Zealand. Uropetala carovei is present in almost all parts of the North Island and ns far south as Lake Wakatipu. In tho nymphal and tho adult stages ' doubtless (ho two species have the same habits. Both are magnificent members of their order. To other insects they are ferocious. To human beings and all volebritcs they are absolutely harmless. Dragonflies are called horse-stingers in the Old *• iiintry, but they do not sting horses nr any other creatures. TTiey have no stings to sting with. Their wings, a rich network of veins, are equipped with largo strong muscles, whoso beautifully correlated action makes tho flight of dragonflies a marvel. They arc tho swiftest insects on the wing. If ancient lineage stamps the, aristocrat, they are - amongst tho aristocratic insects. They have left remains to tell, in part, their ancient history, in some of (he oldest fossil-bearing rocks. In spite of that, their structure is simpler than (lie structure of_ many other insects, and even their life-history—the path from tho egg to tho perfect insect’ —is less complex than tho life histories of moths and butterflies, bees, and wasps. They are children of the light. They so love tho sunshine that they usually conceal themselves in dull arid cloudy weather. Another insect handsome in black and gold sent by Mr J. M. P. Tapp, Matai. near Mangapehfc King Country, is New Zealand’s giant ichneumon fly. It has slender feelers, i s waspish in general appearance, and its long thin egg-laying instrument, springing like threads from the end of its body, proclaims its sox. Ichneumons are notorious parasites on other insects. Tho giant ichneumon, Rhyssa franctinervis, seems to victimise grubs of New Zealand’s elephant beetle. Rhyncodos ursus, a weevil, and, as such, a prominent wood-borer, Mr S. Lindsay, 18 Sydney street, Spreydon, when at Mount Gray, inspected a native beech tree bored with many holes. These, evidently, were made by tho grubs of the weevil, as adults were flying about. Air Lindsay saw a female ichneumon begin to uso her egg-laying instrument. I She was only a few yards away, and a j small telescope helped tho view. Aftei : living around (he tree several times, the i ichneumon alighted at a place she seemed to think suitable for her eggs. Arching her abdomen high over tho thorax, she began to bore into the tree with her instrument. A largo semi-transparent bladder was protruding from tho abdomen at the base of the instrument, and pulsated at intervals. Mr Lindsay does not know tho bladder's ih's, hut suggests that it might inject a liquid through the intrument to help in softening the wood, making : t • a-icr for the instrument to penetrate to ■ , hole in which a grub of the, weevil The e-mil plan amongst ichneumons is :depo.-it their eggs in the grub of anline- ' jn-ei t. The young ichneumon, on hatching from it-- egg. devours its host, ! here i- no record of the methods followed the i< hncuinon sent by Mr Tapp but Mr Lindsay believes that it i= probable that in ibis ca-e the parasite merely place? its ec-ur- in the hole of the weevil "rub, the young ichneumons lining sufficiently ;ictiv,'* TO ron ii tin- grub and devour it. Abliongh ini- ichneumon'-,- egg-laying in--trumen’ -m i-po-itor is it.- proper name—li verv long. Mr lund-ny states that some we'd grub- will be mo deen in the wood lo bo directly accessible to it.