GEEYBACK CAXE BEETLE, LEPIDODERMA ALBOHIRTUM. 13 



That grnlis are most destructive on well-drained soils does not mean 

 that they do not exist in other soils, for quite the opposite is often the 

 •case. Even on the river-Hats, where the soils are normally well supplied 

 with Avater, and the cane seldom shows any injury from gruhs, I have 

 found them to be very numerous, by digging; in one case as many as 

 16 per stool. Naturally we might conclude that this apparent immunity 

 is solely due to the fact that the land has more abundant hunuis ; yet 

 I think a better explanation is that in the event of roots being eaten new 

 ones are more quickly produced in this moist soil to replace them, hence 

 the leaves show none of the withering effect. 



]\rost of these remarks have reference to plant cane, since on badly 

 infested land it is seldom possible to secure ratoon crops. Nevertheless, 

 in some instances the injury to the first crop is slight and the following 

 ratoons are wiped right out. In fact, it is iLsually considered that the 

 grubs are more destructive to ratoon cane than they are to the plant. 

 My experience is that in the latter case cultivation can be carried close 

 up to the plants, and is continued for a much longer period than with 

 ratoons. Therefore, in most instances, if the plant crop is severely 

 injured, there is little hope of securing a profitable ratoon crop the next 

 season. 



Fortunately, if the grubs are with us, it does not signify that they 

 will always be with us. In some districts they have disappeared as if 

 by magic — possibly by disease or other natural cause ; still there is no 

 •ciuestion that they leave the older areas as the timber is gradually 

 -cleared away and the country opened up ; ])ut they usually continue their 

 depredations in the newer fields, which border the feeding-trees, in which 

 ease the "firing line" appears to be only moved back. 



I have neglected to mention that some of the beetles feed for a brief 

 period upon the leaves of the sugar-cane, producing scars similar to 

 those made by cutworms or grasshoppers (Plate 3). They have often 

 been noticed taking their first meal on the cane before flying away to the 

 feeding-trees, but whether this is a customary performance has not yet 

 been demonstrated ; in any event I have never observed any serious 

 injury resulting from it. However, it has been recorded by W. T. Paget 

 (18) that when the natural feeding-trees of the chafers were destroyed 

 at Mackay they ate the cane-leaves; but the reference does not state 

 Avhether the injury was extensive enough to be serious or not. 



Finally, as Try on (19) has pointed out — 



"Failure in the crop, for which the grub-pest has been held respon- 

 -sible, has been partly due to the co-operation of the gumming disease. 

 It must not be inferred, however, that this has always been so, for such 

 an inference would l)e quite contrary to what is actually the case ; much 

 less is it true that the grub-pest manifests a preference for 'gummed 

 cane,' or, indeed, for such as is not in a condition of perfect health." 



HABITS AND LIFE HISTORY. 



The greyback beetles, although usually designated as cane-beetles, 

 are by no means addicted to this crop, for, as investigation has demon- 

 strated, they are apparently indigenous to the country. Hence they 

 naturally exist in the uncultivated grass land ; and from this, under some 

 circumstances, they eventually spread into the cultivated areas, especially 

 where these lie in proximity to suitable trees on which the beetles 

 may feed. 



