26 AUSTEALIAX SUGAK-CANE BEETLES AXD THEIR ALLIES. 



(2) Larvje kept in hare soil pass, for days at a time, large amounts 

 of excrement. This Avonld not he possihle unless food was 

 heing ohtained. 



(3) Larva? kept in hare soil mixed with paris green invariahly 

 die after ahout three days. 



(4) Starved gruhs have never heen found in nature, though 

 coming from bare soil or from some depth beneath the roots 

 of grasses. Larvas obtained from a piece of land maintained 

 for three months in a state of barrenness were as plump as 

 usual, their food canals full of organic matter mixed with 

 soil. 



(5) Grubs are healthy for several months in bare soil without 

 access to living vegetation. 



(6) In cultivated canefields, the larvii?. are often found in bare 

 parts some distance awa.y from living plants and apparently 

 unable to reach same for several days at least. 



(7) Larvae kept in pure sand or in empty glasses commence to 

 shrivel after several days and to die after a week. 



(8) Grubs are not habitually and constantly attendant upon 

 plants. 



(9) Examination of the food canals shows considerable variation 

 in the nature of the contents, which always is a mixture of 

 soil and organic matter of vegetable origin, the organic matter 

 sometimes predominating, often the soil doing so. 



(10) Forbes (1907) states that Stiles has sliown that a certain 

 intestinal parasite of swine passes an intermediate stage in 

 the intestines of white grubs (North American). These 

 parasites must be ingested with soil containing the excrement 

 of swine probably, or by direct ingestion of the excrement. 

 If the ingestion of the soil by these grulis was purely accidental 

 and of small amount, it is most likely that the parasites would 

 be unable to survive, yet they are abundant. It is most 

 likely, then, that they must be habitual soil-swallowers." 



In my experience the grul)s do not necessarily require living roots 

 for healthy development ; in fact, I have found them of maximum size 

 under piles of old, decayed eane-stubble, many of them living right in 

 the old stalks in holes which they have excavated while feeding. Organic 

 matter, however, is certainly necessary for their development. Hence, 

 if they cannot find this in the soil, they natui'ally attack the living roots 

 and even the rootstocks for their supply. 



My observations have been that the grubs are only excessively 

 destructive to sugar-cane when it is growing on land Avhich is deficient 

 in organic matter. Hence, as I have indicated above, the young grubs 

 work as near the surface as the supply of moisture will permit, for there 

 they find the greatest amount of organic matter, i.e. rubbish from the 

 crop, such as old leaves, &e., which are decaying on the surface of the 

 soil. 



Usually the young grubs find sufficient organic nourishment in this 

 way, and do not appear to damage the living roots. But as they increase 

 in size, particularly where grubs are numerous in fields, the available 

 supply of decomposing organic matter is soon used up ; hence the living 

 tissues of the plant are gnawed to such an extent that it suifers seriously. 



