28 AUSTKALIAN SUGAR-CANE BEETLES AND THEIR ALLIES. 



the grubs can exist in snper-satnrated soil, and even withstand immersion 

 for a considerable period — two or three days — they are evidently 

 uncomfortable nnder such conditions. Hence, as has been noted, they 

 move toward the surface when the soil becomes saturated, and I have 

 even found them coming right out of the ground when the surface became 

 flooded. Along the river-liats it is not imcommon to find the grubs 

 pupating very near the surface, in fact so close to the top that most 

 of the pupge may be turned out by ploughing. 



The pupal cell is oval in form, and measures al)out 1 by 2 inches 

 inside, the walls inside being smooth and compact. The black internal 

 lining of the cavity is evidently formed from the soil contents of the 

 alimentary canal, which the grub expels shortly before changing to the 

 pupa. I have frequently dug up grubs just after they had expelled 

 this waste matter when they were on the point of pupating. In this 

 condition they are semi-torpid, and the hinder part of the body, which 

 is normally plump -w^lien filled with soil, is much shrivelled, so that the 

 skin is considerably wrinkled. As is the case with m.ost beetles, the pupa 

 lies on its back in the cavity. 



Our field observations would indicate that there is no regularity 

 as to the time that pupation takes place, for it evidently may occur any 

 time during a period of fully six months. Our earliest record was on 

 16th iMay, 1918, at Greenhills; and the latest, 8th December, mentioned 

 by Girault and Dodd (6C). ^Moreover, available data would indicate 

 that the grubs pupate sooner in well-drained, porous soils than in those 

 containing more clay and moisture. For instance, during June, 1917, 

 I found that approximately one-third of the grubs had pupated by the 

 29th of that month, and, as mentioned above, fully formed beetles were 

 in the chambers by 4th July. And, on the other hand, it was the latter 

 part of August before the pupa? began to be found in numbers in the 

 heavier clay soils near the Mulgrave Eiver. 



As to the duration of the pupal stage, we have little direct evidence. 

 This is due to the fact that specimens removed from their chambers do 

 not develop in a normal manner. Even if they do not succumb to dryness, 

 as is frequently the case, the length of this period is considerably 

 increased. And on the other hand it is a difficult matter to keep them 

 under observation in their natural habitat. 1 think we may naturally 

 conclude, however, from the above observations, that this period does not 

 last much if at all over a month. 



In order to forcibly bring out the known facts in the relation of this 

 species to sugar-cane, we have made use of the valuable suggestions which 

 we obtained from a recent pul)lication by John J. Davis (107). Hence, 

 in Plate 7, we have a pictorial story of the life-history of the pest, month 

 by month, showing both its activities in the soil and air, as well as the 

 effects upon the growth of the cane-plants. Then too, in Plate 8, these 

 facts have been recorded diagrammatically to cover all of the data that 

 we have accumulated on this species. 



