THE GRASS GRUB.

Dominion, Volume 4, Issue 1188, 25 July 1911, Page 8

THE GRASS GRUB.

TtIK INSECT AK'D ITS HABITS. The depredations cf the dreaded grass grub have been very severely felt, particularly .in South and Mid-Canterbury, during the past sea-;on. -Huge areas of pasture have b;eu rendered practically valueless owing to the ravages of the insect in question, aud. in addition to attacking grass the grab has in some cases almost" completely destroyed considerable , areas of autiiruu-sown grain crops. The. 'loss iu Canterbury aloi:e is said to havo already amounted to some thousands of ' pounds, and it is not ended yet. J)r. Ifilgendoi'f, biologist of Canterbury 'Agriculutural College, in an interesting interview with the Christchurch "Press," gives u brief outline of the life history of the grub. The grub, ho says, is tho larva of a beetle which is a native of Jsew Zealand, its scientific appellation being "odoutria Zcalanilica"; it is a cockchafer and belongs to the same species as the European cockchafer, though our insect is a smaller one. Tho beetles emerge generally ab.:ut the first week in November, and for the next six weeks or so are very, busy laying eggs which will provide for the next generation. A fortnight or so before Christmas all the . beetles have finished their egg-laying, and by'the time Christmas is passed most rf ■ tiieni are dead. Tin!' eggs thry have laid usually hatch out in December, but the grubs are. very small, and the. damage Ithey do is hardly noticeable until, about I'May, by which time thpy have grown a ;good deal and cat proportioualely more llrootl. If the season is a mild and genial one, tho grubs live about two inches be-' low the surface of tho soil, but if the season is wet.and the temperature low, ( the grubs burrow downwards to escape the rigours of the climate, and they con«!f(iisritly get below their food region. If the food supply is good, and the. grubs have been enabled to lay up a sufficient, store of nutriment in their bodies to uct as a reserve to take them through their resting stage, they will pupate, that is, turn into a chrysalis alxitit October, and.emerge as a beetle iu November, thus completing their lifo cycle. But if the food supply has been poor, and if they have had* to burrow deep to escape the cold and wet and so have got below that portion of the soil that contains their food supply, then they do not pit pa to iu October, but will hang on until a .second season has passed, and sometimes even until a third. Thus it will be seen that a severe winter, while not perhaps killing many' grubs, will prevent them turning into beetles, and as the beetles, by laying eggs, provide the increase, the fuel that few, if any, booties emerge after a.

severe season, is a great check to the pest Sor a time, as it. prevents the multiplication of the species. Tho fact that few beetles emerge after a cold, wet season does not mean that the grubs have been killed,