NATURE NOTES.

New Zealand Herald, Volume LXVII, Issue 20626, 26 July 1930, Page 1 (Supplement)

NATURE NOTES.

HABITB OF THE OICADA.

BT 3. DBrKMOND, F.L.8., V.t.l.

Mr. 0. B. Walker, of Taupaki, noticed a tea-tree twig with the bark cut as if by a wound and the wood exposed Down the wound there were about twelve strange carvings like Vs. "At first, I thought that the wound was an ordinary chafe, but later I noticed the strange pattern," Mr. Walker states. " What made it ? I had never seen anything like it before. Both ends of the wound seemed to be alike, so I cut one oft smoothly, to see if I could learn anything about it that way, but it was no good. I shall worry about it until you kindly explain."

The explanation is that a cicada—one of the insects called locusts, which play their musical instruments droningly on treos and shrubs in the summer sail—selected that twig as a suitable place in which to deposit her eggs, and carvd it on the pattern disclosed. She probably, was one of the large tree-dwelling cicadas, Melampsalta cingulata, which favours woody plants like the tea-tree rather than twigs of shrubs in undergrowth. It is this cicada that makes the loudest choruses in New Zealand, singing vigorously and continuously, and often Invisibly, as the bark on which it usually rests harmonises with its colour.

Dr. J. O. Myers, who has studied New Zealand's cicadas more closely than anybody else has studied them, watched a cingulata depositing her eggs in tissues of a twig 01. a midsummer day in the North Island A cicada usually takes her stand with her head pointing up the twig, out from the trunk. This one worked with her head pointing down the twig. For a long time, with her body arched, and evidently exerting great force, she drove her egg-laying instrument slantingly into tho twig. Her body pulsated rhythmically. With much effort, the instrument was withdrawn, all except the extreme point, but was driven in again, with slightly less effort than on the first occasion. She repeated this performance ten times, eacli thrust taking less time than tho previous one. The tip of the instrument never left the hole, and always it was driven in un to the hilt. At the end of the last thrust, the instrument was completely withdrawn. The next instant the cicada had gone. Twenty minutes elapsed between the first thrust and the departure. She left behind a row of egg-nests, marked by frayed wood-fibres that covered the pockets in which the eggs had been laid. The wound that excited Mr. Walker's curiosity is best described as having a herring-bone pattern. This seems to be caused by the hark between a series of pockets break ing and dying.

Different species of--cicadas select different plants as nests for their eggs. One species selects, perhaps not exclusively, the kuromiko, one of the handsome veronicas. The eggs are laid over an urea of about an inch in small circular openings, unlike the pattern made by cingulata, but, if the. twig is split, there is seen in the wood beneath the bark the typical herring-bone pattern. In other countries, cicadas prefer dead twigs. All New Zealand cicadas seem to prefer live twigs. When live twigs operated upon were broken off, the cicada's eggs in them shrivelled and died. The famous seven-teen-year locust—a cicada—of North America, almost always selects a live twig. It was once claimed that the eggs depended on the moisture of the tissues of the plants and that they would not hatch if the twig containing them died.

In any cas#, this instinct sometimes is aberrant A cingulata laid her eggs in a large apple, more than 100 of them, leaving a large wound. A small New Zealand cicada thrust her egg-laying instrument into a stem of ryegrass, withdraw it leisurely, climbed slowly up the stem, and tlew away without depositing any eggs. Apparently, she tested the suitability of the plant, or made a mistake. Members of the same species, kept in a cage, readily laid their eggs in stems of wheat ftrown for the purpose. A mistnke certainly was made by the cicada that alighted on the iron-rod of a bridge and tried to insert her egg-laying instrument into it. She actually produced seven eggs. Some stuck to the rod, others fell to the ground. Another cicada thrust her instrument completely through the stem of a plant, to find, to her surprise, that it was hollow. Holes containing many cicada eggs have been seen in the boards of the roof of a shed. A cicada that would not observe the rule to "down tools" during the dinner hour punctured the handles of some hoes so profusely that they had to be sandpapered before they were used.

Amongst cicadas In France, Fabre found that thoy always drive their instruments downward and lengthwise. Each puncture, he states, is a slanting cell, bored usually into the pith of a stem. The entrance is not closed, except by a bunch of fibres parted when the eggs are laid and coming together again when the instrument is withdrawn. Sometimes there may be seen gleaming through the threads of the covering a tiny glistening speck. It looks like a glaze of dried albumen, apparently a secretion that accompanies the eggs or facilitates the play of the instrument. The average number of eggs in ench cell counted by Fabre was ten. The number of cells of a complete laying was between thirty and forty. In that case, a single cicada produced between 300 and 400 eggs at a time.

In Fabre's garden, each cicada had a stalk to herself. She always came alone. There was no competition for the suitable places. There was no quarrelling. Peace prevailed. If a cicada appeared and found the site occupied, she discovered hor mistake, flew away, and looked elsowhere. They were so absorbed in their task? that Fabre watched them through a lens He saw an instrument with its double augers dig and disappear in the wood with a gentle movement, almost im perceptible When the eggs were laid, the instrument was withdrawn with deliberate slowness, in order that it sho ild not be warped The hole closed i I solf as the fibres came together again. The cicada climbed a little higher, in a s'might lino There was another punch with the instrument, a fresh cell was made, and another batch of eggs was laid.

The rulo seems to be for cicadas' eggs laid in summer to hatch in the following autumn, or oven late in the same summer. Egg nests collected on marram grass in New Zealand on December 31 j rod need Viiung in the middle and end of February. A batch of eggs laid in captivity in cocksfoot in New Zealand on January , hatched almost in a mass on 1 The eggs are white when laid Befoie hatching they usually become pink, lnis is the colour of the newly-born young, called nvmphs Hatching in mass is the rule A nymph comes out of its egg clothed in a thin glistening membrane. \o sooner is the open air reached than this garment is cast. Very soon after batching, n nymph falls to the ground It does not take nourishment from the tissues of the plant on which it was born Cicadas operations do not directly injure trees, although, by cutting the bark with their instruments they may weaken branches and cause tliein to fall off, or they may give accosa to tho spores of i fungi.