Part 20

During the spring months great quantities of little stick insects may be noticed on the parasitic ferns covering the tree stems in the forest; they are curious little animals, their antics when simulating inanimate twigs being often most amusing, and if the reader wishes to investigate a comparatively untouched branch of entomology he cannot do better than keep a number of these until mature, when he will doubtless contribute much to our scanty knowledge of this curious family.

{112}Family ACHETIDÆ.

Acheta fuliginosa (Plate XVIII., fig. 1).

This destructive insect is not indigenous to New Zealand, having been introduced from Australia into the Nelson district many years ago. Strange to say it has never been seen in Wellington, where specimens must be constantly landed amongst produce, &c., but appear to be unable to effect a settlement, owing, probably, to some peculiarity of the climate which renders the place unsuitable for them. The larvæ may be first observed about December, when they are often seen hopping about the vegetation. They are extremely obnoxious, devouring everything, and frequently entering houses, where they consume provisions, clothes, and even boots. During the summer of 1875 the farmers round Nelson were fairly eaten out by this insect, the cattle absolutely starving for the want of food, but since that time the pest seems to have gradually diminished, although it is still very injurious to many garden plants.

The illustration (Fig. 1) is taken from a female, the male wanting the long ovipositor. These insects appear in the imago state about March, and continue in great abundance until the end of summer, the cold weather which generally sets in about the beginning of May rapidly destroying them.

Family GRYLLIDÆ.

Deinacrida megacephala (Plate XVIII., fig. 2 , XVII., fig. 8 ).

This conspicuous species is especially interesting, as it may be regarded as the type of a very peculiar assemblage of apterous crickets, pre-eminently characteristic of New Zealand. It is very abundant round Wellington, and may be occasionally taken under logs, &c., but is best procured {113}from the hollow stems of various trees, where it is found inhabiting the deserted galleries of wood-boring species--frequently enlarging them to suit its own requirements.

The plant most usually selected by these insects is the mahoe (Melicytus ramiflorus), whose stems may be often seen pierced with large holes. Out of these the insects emerge at night to feed on the leaves. To extract a number of specimens, without injury, requires considerable care, and is best performed with a small axe, which should be first used to cut in about three-quarters through the trunk, just below one of the holes. Another notch is then cut about a foot lower down, and the intermediate wood split off in long pieces, until the tunnel is laid bare. On approaching an insect the first thing seen are two red threads, which are the antennæ, laid back as shown at Fig. 8. A deep notch is then cut into the trunk, some nine or ten inches below this point, and the piece bodily wrenched off. If the individual thus treated is a male he will cling firmly to the log, elevating his hind-legs in the air and biting viciously at anything within reach, but the females, in the majority of cases, endeavour to escape and hide themselves under the leaves, &c., on the ground. Both sexes when irritated emit a peculiar grating sound, which may be often heard at night in the forest, and is produced by the friction of the femur against a small file situated on each side of the second abdominal segment. They can also leap a short distance, but not so far as many of the smaller species (Libanasa macropathus, &c.). They are evidently strictly arboreal in their habits, as they exhibit great skill in walking along branches, and will climb up a thin stick with wonderful rapidity.

When in their burrows the posterior legs are extended behind the insect and push, while the anterior and intermediate ones are thrust forwards, the claws being firmly inserted, so as to enable the insect to pull itself along. {114}Travelling along the burrow in this manner, they frequently evade all efforts to extract them, until they are stopped by arriving at the end of the gallery.

The sexes of this species are readily distinguishable, the male (Plate XVIII., fig. 2) possessing an immense head furnished with a pair of enormously powerful mandibles. The female (Plate XVII., fig. 8) is a more attractive insect, her gracefully curved ovipositor and smaller head having a much more pleasing appearance than the terribly menacing jaws of her mate. Both sexes are able to give severe bites, but it is extremely doubtful whether they would prove anything worse than slight mechanical injuries, as the insect is not likely to be poisonous. I am, however, unable to speak from experience.

Family GRYLLIDÆ.

Xiphidium maoricum (Plate XVII., fig. 1).

This pretty insect may be found in great abundance round Nelson during the autumn, but is rarer in the Wellington Province. Its presence may be at once detected by the curious chirping heard in various directions shortly before sunset and lasting till eight or nine o'clock in the evening. This sound is produced with the wing-cases, which the male insects may be seen vigorously rubbing together. The females are quite mute, and they may be also distinguished by possessing a short curved ovipositor at the end of the body. The peculiarly leaf-like shape of the insect and its bright green colour render its discovery amongst the herbage a most difficult matter, even when its whereabouts is indicated by its cry--in fact, were it not for their music, there is little doubt that very few of these insects would ever be captured, as they are practically invisible, and are an instance of protective resemblance carried to great perfection.

When disturbed these crickets fly about twenty yards {115}and again settle in a bush or amongst herbage, carefully avoiding alighting on the ground where they would be readily visible. Their flight is somewhat feeble for such large insects. Great care must be taken, when capturing specimens for preservation, not to hold them by their powerful hind-legs, as they will not infrequently cast one off while endeavouring to escape.

I have not yet noticed the larva of this species, but should imagine it would closely resemble a wingless imago.

Family LOCUSTIDÆ.

Caloptenus marginalis (Plate XVII., fig. 4).

This is the little grasshopper which rises before our footsteps in swarms on a hot summer's day; it is one of the last insects to leave us in the autumn, being frequently found in warm situations on fine days in the middle of winter. Owing to its great abundance this species must inflict considerable damage on the grass, as it has taken up its quarters like the English grasshopper in the cultivated fields, where an unlimited supply of food is always at hand. Formerly, no doubt, it was much less common round Wellington than at present, owing to the few open spots then existing, none of these grasshoppers being found in the forest.

The perfect insect may be recognized by the rudimentary wings which are present on the thorax, thus causing it to closely resemble the larval form of many of the winged species, and for which it might readily be mistaken were its true character unknown.

Family LOCUSTIDÆ.

Oedipoda cinerascens (Plate XVII., fig. 3).

This large and conspicuous insect occurs abundantly in all open situations near Nelson, but is very rare in the {116}Wellington district, becoming, however, again common further north.

When disturbed it leaps into the air, spreads its wings, and flies away with great rapidity for thirty or forty yards, when it alights, and allows its pursuer to get within a few yards of his prize before again making off. This habit renders the capture of a good series of this insect a most arduous matter. The sexes may be readily distinguished by their size, the female being nearly twice as large as her mate.

This species is very variable in colour, some individuals being dark green whilst others are of a uniform drab.

The food of this insect consists of various domestic grasses, but I do not think it is at present sufficiently abundant to exercise any harmful influence on agriculture. By some entomologists, however, it is regarded as only a variety of the renowned migratory locust (Locusta migratoria), and as such its advent in large numbers might be viewed with serious apprehension.

It is also strange that although I have often seen large numbers of this species in the perfect state I have never observed the larva. I can only conjecture that the insect breeds in very secluded localities and then migrates in search of fresh food supplies.

Group EUPLEXOPTERA.