Dominion Museum Notes THE DESTRUCTIVE HUHU

Dominion, Volume 30, Issue 255, 24 July 1937, Page 2 (Supplement)

Dominion Museum Notes THE DESTRUCTIVE HUHU

Its Wood-Boring Grub Was Regarded as a Delicacy by the Maoris

Sometimes on summer evenings housewives are startled by a large and noisy intruder, an enormous insect which, attracted by the light, comes whirling in uninvited at the open window. In noisy flight, droning like a miniature aeroplane, it goes round the room, bumping blindly against walls and ceiling, until finally it settles clumsily on curtain or carpet. Then it is seen to be a big, brown beetle, perhaps two inches long, its shiny wing-cases veined with yellow, its body furry, and its head crowned with a pair of antennae nearly as long as the rest of its body. It is the “huhu,” king of New Zealand wood-destroying beetles. Its giant grub is still regarded as a delicacy by the Maori people.

The Huhu Beetle. These beetles vary enormously in size. Some of the largest and also some of the smallest beetles found throughout the world belong to this group. New Zealand’s largest beetle, the “huhu,” scientifically known as Prionoplus reticularis, is a longicorn which should b.e familiar to everyone. It is readily attracted by artificial light and frequently enters houses, where its presence is at once betrayed by the loud, droning noise of its flight.

Actually, it is the larva or grub of the beetle that does the greater part of the damage to timber. This grub is a long, creamy-coloured, fat, fleshy creature, known to the Maoris as huhu and regarded by them as an item of great dietetic delicacy. The eggs are laid in crevices and cracks in trees and under bark; the huhu, on hatching, bores throughout the sap-wood first, and later, as this is eaten away, will commence to attack the heart-wood. However, when ready to pupate, the larvae move to just under the surface of the wood, and, on emerging, the beetle cuts its own way out, leaving a large oval exit hole which is the only outward sign that a tree has been attacked.

The huhu attacks mainly dead trees, generally rimu, matai, kauri, white pine among natives, and English oak and insignis pine among exotics.

The Lemon Borer. A close relative of the huhu is a ’smaller, narrow - bodied longicorn, Aemona hirta, which has come to be commonly known as the “lemon-tree borer.” This native beetle is about one inch long, brownish in colour, and covered more dr less with golden hair. There are several orange-coloured spots on the head and one on the centre of the back. The grub is similar in appearance to the huhu, but smaller and narrower-bodied. It drills through the centre of the stems of trees and also cuts deep burrows, encircling a branch, and frequently causing it to snap off.

This beetle attacks a number of native trees in the living state, such as wineberry and manuka. It also attacks a number of imported trees, including poplar, lucernes, willow, citrus, almond, gooseberry, and apples.

Two-toothed Longicorn. Among borers attacking wooden buildings and furniture, the native species, \Ambedontus tristis, commonly called “the two-toothed longicorn,” is outstanding both from the nature of its attack and from the extent of the damage which can result. In its normal existence this beetle lives in dead trees in

Let us devote our attention for a moment to the cerambycidae or longieorn beetles. The members of this family are readily recognised by their relatively long antennae or feelers, which, in some species, are even longer than the body. Longicorns form a very large family of wood-boring beetles, distributed worlcl-wide, and represented in New Zealand by quite a number of native species. Most longicorns attack standing timber, their larvae drilling long, winding passages, preferably throughout its sap-wood, but as this becomes eaten away most forms will commence to attack the heart-wood also.

the forest, but of late years it has developed a decided taste for milled timber, the wood attacked being chiefly rimu, kauri, matai, macrocarpa, and Oregon pine. The beetles are on the wing during February and March, and are about half an inch in length, somewhat red-dish-brown in colour, with a clothing of more or less golden hair. On each side of the thorax, just behind the head, there is a relatively large spine. The female beetle lays h.er eggs in batches, which are placed in tiny holes made in the surface of the wood by means of her ovipositor. These holes may be clearly seen with the aid of a moderately strong magnifying glass. The very small larvae which hatch from these eggs burrow directly into the wood, their minute burrows being easily distinguished on a piece of plan-

ed timber with the aid of a strong lens. These larvae burrow with the grain; and their burrows may run for .many feet. In this way joists, studs, or floor-ing-boards, etc., may be under severe infestations reduced internally almost to powder while appearing on the surface perfectly sound. The burrows made by the larvae are packed with wood dust as they move along. When ready to pupate, the larvae turn toward the surface, cutting across the grain of the wood. The beetles emerge and cut their own way out from ,the wood,, leaving small, oval-shaped exit holes which measure about one-third to one-flfth of an inch in diameter across their widest part. Owing to the manner in which these larvae may travel many feet from the original infested area, it often is difficult to locate the limits of their damage, particularly as they may pass from one board to another where these are joined or in contact in a building.

There are other native longicorn beetles, and several introduced species which from time to time have been reported as doing damage of economic importance. Many of these, together with those above mentioned, are on view in the entomological section of the Dominion Museum, where, ns far as possible, displays illustrating the type of damage done by the various species are show.n as well.