Life History of Beetle

By B. A. O'Connor, Senior Entomologist in Fiji.

The damage done by this pest is all caused by the adult beetles, the grubs being quite harmless.

The beetle flies to the top of a palm, and crawls in among the bases of the fronds. It then bores in towards the centre, making a large hole through the butts of the younger fronds, and pushing out of the hole a mass of chewed fibres.

If it reaches the growing point of the palm, no new fronds are formed, and the tree dies. It has a typical appearance of having outer fronds but no inner ones.

Even if the beetle does not reach the growing point, rain-water may lodge in the burrow which it has made, and bacteria and fungi grow ing in the damp pocket may cause the growing point to decay.

Where the beetle has chewed through the young “spear” of de veloping leaves, it damages the fronds so that when they open out they either have the tip cut right off or have a triangular section of leaflets removed.

A heavy? fall in production is caused by the death of palms and the loss of foliage. Moreover, the mortality among young palms is very heavy, so that replanting be comes extremely costly. The pro ducer may reduce his losses con siderably by trapping beetles and by destroying breeding places, but this involves him in heavy ex penditure.

Breeding takes place in decaying vegetable material, such as the tops of standing dead palms of various kinds; in rotting stumps and logs of palms and other trees, includ cluding rubber trees; in coconut trunks used in bridges, buildings and other structures; in dead Pandanus; in rubbish dumps and compost heaps; in heaps of farm yard manure; in piles of rotting sawdust; in old, covered-in latrines; and in other similar situations. De caying sago trunks may also be a possible breeding place.

The beetles mate in these places, and here also the females lay their eggs, each female producing up to sixty or seventy eggs. The eggs hatch within a fortnight, and the grubs, which feed on the decaying vegetable matter, become fully grown in from 2h to 3 months after hatching. A cell is then con

structed, either in the food-material or more commonly underground, and the pupa, or resting, stage is formed. This stage lasts about three weeks, when the adult beetle is formed. The beetle remains in the cell for a further three weeks be fore emerging. The female pro bably lays eggs within a fortnight of emerging. The total length of a generation is thus about five months.

The beetle is nocturnal in habit, flying only at night. Some author ities state that it is strongly at

tracted to light, but there is evidJ ence that this attraction is only moderate. However, some of the beetles do fly to lights.

The adult beetles feed on manyl kinds of palms, including the coco-! nut palm, oil palm, nipa palm, sago palm and Areca or betel-nut palm, on Pandanus and, to a small ex tent, on sugar cane and sisaL hemp. Caged beetles have freely’ eaten pineapple, pawpaw, dale* (taro) and banana, though there! appears to be little attack on these plants under natural conditions. I