WILD LIFE IN NEW ZEALAND

Otago Witness, Issue 3500, 12 April 1921, Page 54

WILD LIFE IN NEW ZEALAND

Br tub Hon. G. M. Thomson, F.L.S.

No.

111.

In the slimmer months in all lowland districts where ditches, pools and waterholes abound, Dragon-flies are to be seen on any bright and sunny day. They are characterised by features which at once command attention; they generally have a large and usually brightly-coloured body, of somewhat singular but graceful form, borne on gauze-iike wings and they fly with great strength and swiftness. They appeal to all who have eyes to see and they have been utilised by the poets in vivid imagery. Tennyson tells how Sir Gareth loosed A cloak that dropt from collar-bone to heel, A cloth of roughest web, and cast it down, And from it like a fuel-smothered fire, That look’t half dead, brake bright, and flash’d as those Dull-eoated things, that making slide apart Their dusk wing-cases, all beneath theie burns A jewell’d harness, ere they pass and fly. Of course this might apply to many gaudy insects, but the following is more direct : To-day I saw the dragon-fly Come from the wells where he did lie, An innner impulse rent the veil Of his old husk; from head to tail Came out clear plates of sapphire mail; He dried his wings; like gauze they grew, Through crofts and pastures wet with dew A living flash of light he flew. Beautiful savages these insects are for if we catch one and open its mouth, we shall most probably find it filled with a mass of small insects which it has caught and which it will masticate at its leisure. All through its life it is a savage. The larva lives m water. It is not at all an attractive creature, and it moves rather slowly, clinging to the water weeds by its legs, and often lying still for hours. But though so quiescent, it is always on the watch for prey, and its sombre colouring and motionless attitude constitute the real danger to the creatures which come within its range. As soon as the victim, whether an insect, snail, tadpole, or even a little fish comes within range, the larval, dragon-fly shoots out an arm-like appendage from the head, and seizes its prey'. This organ, according to Miall, is a peculiar modification of the third pair of jaws. It is a murderous weapon and is most effective in its action. It is appropriately termed ‘the mask” by entomologists. for it evidently hides the predatory intentions of the animal which possesses it. In our largest dragon-fly the larva or nymph is over two inches long. Most naturalists who have studied dragon-flies have taken notice of the breathing apparatus of the larvae. They not only depend for their air-supply on spiracles or tracheae in the thorax and abdomen, but also in some species on minute rectal gills. If the water in which they live does not contain sufficient dissolved oxygen for their use they thrust the posterior end of their body into the air, and so expose the openings of the breathing organs. I do not know the life histories of the various New Zealand dragon-flies, nor do I think that any one here has worked them out. There are about 10 species in the country, but only three are really common. Surely everyone knows the large shining black and yellow dragon-fly, which is so common in the summer months in all parts. This fine insect is about four inches long, and its beautifully veined wings have a spread of between four and five inches. The female is rather the larger of the two, and the males are readily recognised by two small leaf-like appendages at the extremity of the abdomen, and these are spread out during flight. The sexes are therefore easily made out when on the wing. The body is rather blackish-brown than black, with paired bright yellow markings on the thorax, and irregular yellow bands on each abdominal segment. Mr Hudson has met with this species in the Kelson Mountains at an elevation of 3,600 feet. This well-known New Zealand entomologist says—“ Tile food of the dragon-fly consists of living insects, which they capture on the wing by their own superior powers of flight. The exact mode of capture is not known with absolute certainty, owing to the extreme rapidity of the dragon-fly’s movements. It is certain however, that they capture flying insects, and it seems most probable that this is done by means of the legs. These are inserted so as to be close to the mouth, they are directed forwards, and are held bent at right, angles so as to form a sort of net, and are armed with a beautiful system of fine spines ; it is probable that if the dragon-fly pursues an insect on the wing, and strikes it with the trap formed by its six legs, then these immediately come under the mouth, so that the victim, directly it is captured by the leg trap of its pursuer, finds itself in the jaws of its destroyer. The excessive mobility of the head permits the victim to bo instantly secured by the mouth, and the raptured this turned about by this and tile front pair of legs, and is nipped rapidly, so that the wings and drier parts fall off, the move juicy parts of the prev are speedily squeezed into a little ball which is then swallowed or further compressed by the mouth for the extraction of the juices.” Mr Hudson goes on to say—“ The wonderfully rapid and perfect flight of the dragon-fly has led A mans to sugtrcft that its mechanism would form a suitable model for a flying machine to be propelled by electricity.” This sentence was published in 1904, and there is no dou lit that the Structure of the dragon fly was fully considered when the first aeroplanes were under construction. Besides the big species, which is technically known as Uropetala. earovei, the first name referring to the petal like appendages of the abdomen, there are three other well known species. Romatochlova smithii is about. 2in long, with a wing expanse of 2?in. The head and thorax are bronzy green, with yellow

sides but in cabinet specimens they look almost blue. The abdomen is black with paired yellow markings towards the side of each segment. Inis is another very switt, strong flyer. Mr Hudson thinks that the females are probably eaten by trout during the process of egg-laying, ag they beat tne body violently on the surface whi.st doing so. He attributes the steady decline in numbers in the Wellington district to thio cause, and to the trout eating the nymphs, “though it would seem difheuit for the fish to discover on insect so retired in its habits.’’ I think it more probable that the clearing and draining of the ground in the neighbourhood of settlements is a more likely cause. Lestes colensoni is another dragon-fly. Its body is about l|in long, and the expansion of the wings slightly over 2in. The male is dark purplish black in colour, with brilliant blue markings; while the female is a dull slaty black, with two white bands on the thorax. The abdomen is green at the base and dull purple towards the tip, with whitish bands at each segment. Perhaps the commonest of all the dragon-flies is the small red Xanthagrion zeaiandicum. In this species the body is long, and the wing expansion l|in. It is best recognised by the brilliant red abdomen of the male, while the thorax is black with red lines. The female has yellow lines in the black thorax, and the abdomen :s bronzy black above. This insect only flies on bright sunny days. Mr Hudson thus describes the process of egg-laying—- “ During this operation the male retained hold oi the female by means of his anal clampers, the two insects resuming the “straight line’’ position. After selecting the stem ut some water-plant or similar ooject extending downwards beneath the water, the temaie slowly moved backwards aiong tne stem towards the water, pulling tne male alter her. First the extremity or uer oouy came m contact vvitu tne water ; alter wards both urects continued to move backwards, until the whole of the female was submerged except her thorax and the t.ps ol Her w.ngo. at this time tne temaie frequently struck tile extremity ol her buoy against tne stem and leaves of the submerged portion oi tne plant. This action was no cioubt actual oviposition, though I wuis unable to positively prove it. The female still continued to move backwards until she was at last wholly submerged and the male s abdomen half in the water. At this stage the male loosened his lioid and the female went sti-1 deeper into the water alone, and did not return to the surface tor at least 30 minutes. . . . i lost sight of her amongst the watercress in the tied of the stream. . . . Whilst submerged the female is covered with a coating of air, which of course looks silvery-wh.te- below the water. This air, is no doubt, retained by the. integument, assisted by the numerous bristles and hairs which are situated thereon. ’’ I started out to write about some of the insects to be found m pools and streams, and have only, so far, dealt with two types —viz., Caduis-tlies and Dragon-flies. 1 do not know sufficient about other forms belonging to the same great order of Neuroptera to do more than write generally about them, but they are well worth studying, not only f'or their own sake, but also on account of their importance from an angler’s point of view. In Mr Hudson’s beautifully illustrated little manual of the New Zealand members of this order, published 18 years ago, he gives interesting information about the relation of these insects to trout. The stomachs of 60 trout all taken in streams in the Wellington district, were examined. These were found to contain altogether 5460 identifiable insects —viz., 48C4 specimen!; of Neuroptera, 590 kinds of kettles, 42 flies, 23 Cicadas, 4 ants and 3 grasshoppers. The Neuropteroid insects were 4241 caddis-worms, 529 May-flv nymphs, 18 “Black-creepers” and 16 Stone-flies. In addition there were 21 snails 4 spiders 2 fish and 1 crustacean. Let me conclude this paper with a few notes on these other forms. May-flies are technically known as Kphemeridae because the perfect insect has a very brief life, often perishing on the day it emerges from the pupa. According to lloamur, “some do not even see the light of the sun; they emerge after he has set, and die before he rises again ; others live an hour or even half an hour.” Their larvae live in water. They have a flat body, with plumose branchiae on the sides, and long plumose tail bristles. They creep about mostly on the undersides of stones, but some of the larger forms burrow in the banks of the stream or pond that they inhabit. They are very favourite baits for fishes, ns most anglers know. They used to be very common in many of our streams, but are now sorely decimated by the trout. The adult May-fly takes no food. When they emerge from the water, their alimentary canal becomes distended with air, and this seems to render them as light as fragile balloons, for they perform beautiful aerial dances in the twilight of the summer evenings. T he perfect insects are imitated by artificial fly-makers under the name of “spinners,” and the subimago condition- —that in which the insect rests just before it throws off its last delicate skin and takes flight—as "duns.” The insects known to anglers as “Black Creepers,” are the larvae of a species of Alder-flies. The perfect insect is from 1 to Ijin long, with a wing expanse of, as much as. 3iu in the female. The body is dull reddish-brown, in colour, and the wings are pale brown with dusky clots on the veins. They arc slow, heavy fliers, but they seldom go on the wing till about dusk, and lienee are not readily seen. The larvae are very familiar to anglers. They are often abundant under stones in the bods of streams, where they prey on aquatic insects of all kinds, but especially on the larvae of May-flies. The Stone-flics arc fairly common in New Zealand. They are pretty insects, the brown body carrying a pair of bright' green fore-wings, and a broader pair of pale green hind-wings, which have an expansion of about 2,hr. They are only found in the spring months. The larvae live in rapid streams, where they run

about on the stones very actively, holding on by their legs. They feed upon the larvae of other insects, especially of MayThe study of the life histories of all these aquatic insects is an interesting one for its own sake, and it has great economic importance from the angler’s point of view. 1