WAYS OF THE WILD.

Auckland Star, Volume LX, Issue 10, 12 January 1929, Page 1 (Supplement)

WAYS OF THE WILD.

A NATURALIST'S NOTEBOOK.

THE GIANT ICHNEUMON FLY.

(By A. T. PYCROFT.)'

Mr. A. T. Zeigler, of Tβ Pohu, Hawke'e Bay has sent me a specimen of one of the ichneumon flies. It has been identified by Mr. E. S. Gourlay, first assistant entomologist of the Cawthorn Institute as Bhyssa Fractinervis, the giant ichneumon, and is parasitic on the elephant weevil Rhyneodes Uasus. Several thousand species of ichneumon flies are known to science and there are some seventy varieties in New Zealand. The name ichneumon is derived from the Greek, meaning the tracker, and was first given by scientists to a carnivorous mammal of the genus Herpestis, on account of its habit of tracking the footsteps of crocodiles and hunting out their eggs. The name was later given to any Hymenopterous insects of which the female tracked down and deposits her eggs upon or in the bodies of other insects, such as spiders, caterpillars, plant lice, etc. The larva lives upon the internal tissues of the insect in which it is parasitic, and finally kills it. Hence, many of the ichneumons are beneficial to agriculture by destroying noxious insects. Enemies of Spiders.

Ichneumon flies are universal eueniies to spiders' eggs. An examination of almost any species of spiders' cocoons, will show a large proportion to contain ichneumon larvae. The ichneumons, which thus regard the spiders' egga as convenient food for their own larvae, are probably very numerous, nor are they themselves always free from parasites. Occasionally the larvae of minute Hymenopterous insects are found to be parasitic upon the eggs of an ichneumon which have been laid in a spider's cocoon. It sometimes happens that the development of the young spiders has so far advanced at the time of the ichneumon's intrusions that the latter'a object is frustrated and its offspring, instead of devouring, is devoured.

Mr. Stuart Lindsay records in "The New Zealand Journal of Science and Technology" his observations on a female of the giant ichneumon ovipositing in a dead beech tree, Nothofagus solandri, which was badly bored by elephant weevils. The insect, after flying round the tree several times, finally alighted on what it appeared to consider a suitable spot, after feeling round a good deal with its antennae, which were kept in rapid motion, the abdomen was arched high over the thorax, and the insect started to bore into the tree with its ovipositor. It was at this stage a very striking incident was noticed. At the base of the ovipositor, a large, semi-transparent bladder or sac was-protruded from the abdomen, and this kept pulsating at intervals. Mr. Lindsay's suggestion as to the function of this organ, if not an abnormal occurrence due to rupture of the abdominal wall, is that it might be for injecting some liquid through the ovipositor as an aid to the softening of the wood, and thus assist in penetrating to the burrow of the weevil larva.

Method of Laying Eggs. Sharp, in "The Cambridge Natural History," states that the Ophionidae, to which family of Hymenoptera the giant ichneumon fly belongs, leave larvae which are external parasites, attaching themselves to the body of the host larvae by a viscous secretion. This may suggest that the ichneumon fly simply lays its eggs in the burrow of the weevil larvae after penetrating to the burrow with the ovipositor, and that, on hatching, the young ichneumon larvae are active enough to reach the desired host. This seems probable, as some host larvae will certainly be far too deep in the timber to be directly accessible to the ichneumon's ovipositor, in spite of its great length, which, in the case of the specimen sent me, measures one inch, whereas the total length of the body is three-quar-ter of an inch. The male of this species is much smaller and lighter in build than the female and not go strikingly banded with yellow. Some insects of the genus Rhyssa and Thalessa have an ovipositor three or four inches in length, and, like our giant Rhyssa, are parasitic on speciee of a family which lives in solid wood. The ovipositor is not only of extreme length, but is also furnished with serrations on its apical part, or tip, so that it forms a very effective apparatus. It is brought into use bv being bent on itself over the back of the insect so as to bring the tip vertically down on to the wood, through w-hich it is then forced by a series of efforts. The sheaths do not enter the wood. The egg is laid anywhere in the burrow, the young larva seeks its prey, and lives on it as an external parasite. The young ichneumon flv may sometimes find itself buried in solid wood to a depth of about two inches. In that case it excavates the wood with it mandibles, and should it fail to gain the exterior after three days of work, it dies,

Most of the epecief of ichneumon live inside the larvae of Lepidoptera, and thus keep the myriads of caterpillars within bounds, the number of these destroyed by ichneumons bein" prodigious.

Methods of Obtaining Godwits. I am indebted to Mr. E. W. D. Matthews, Kaitaia, for the two following means adopted by the Northern Maoris to obtain godwits (kuaka). One method was to sharpen hundreds of sticks about 2ft long, leaving a knob at the other end to which was attached a noose of green flax, the noose being about Gin in diameter. The sticks were etuck in the sandbank at low water, parallel with the incoming tide. The birds approaching to settle down would alight and then run some little distance forward, and not seeing the noosea, would become ensnared. Another method was adopted at night. It was known that the kuaka settled in little hollows to sleep. The Maori name of such a place is puta. A dark night was chosen. The birds were surrounded by natives bearing small dry manuka torches. The birds would be set upon and dispatched with eticks, while bewildered by the torch lights. The tuaka's resting-places were above high water mark, just above the beach. The Barawa people state the kuaka told them how to come to New Zealand.