7G AUSTRALIAN SUGAR-CANE BEETLES AND THEIR ALLIES. 



excessive moisture may prove their undoing. As an instance of the first 

 we have the following interesting observations by ]\Ir. Jarvis (80) : — 



"A noteworthy instance of direct control brought about by hot 

 weather occurred towards the end of this month. On the 19th instant, 

 we experienced a maximum dry temperature of 95° F., followed on 20th 

 instant by 98° F., the wet bulb on both days registering 86-5° F., while 

 the wdnd was from the warm quarter (N.W.). During the morning of 

 the latter day, cane-beetles {L. alhohiriuni) became strangely agitated, 

 and instead of remaining, as usual, on their food plants, were observed 

 to be taking short erratic flights, or congregating on the shady side o£ 

 tree-trunks, evidently in a vain attempt to discover a cool resting-place. 

 Later, in the afternoon, a party of blacks who were collecting at ]\Ieringa 

 told the manager of 'Carrah' plantation that large numbers of cane- 

 beetles were dying and dropping from the trees. 



"Finding their account to be correct, Mr. Greenaway communicated 

 wdtli this office, and the matter received personal investigation. Upon 

 reaching the locality in question, the ground was seen to be strewn with 

 dead greyback beetles, mostly under or in the vicinity of JMoreton Bay 

 ash trees (Eiicahjpttis tesselaris) . No less than 25 were collected from 

 beneath one gum-tree of medium size, and in a space containing two 

 square chains taken at random on forest land, Mr. Iladley picked up 98 

 specimens. Of these 27 w-ere males, 49 females, and 22 of undeterminate 

 sex owing to injury by ants. The above area was hastily examined, so 

 no doubt we overlooked several specimens hidden among herbage, &c. 

 The occurrence of such heav>- mortality acquires additional interest 

 from the fact of its having happened about seven days after the emer- 

 gence of these beetles, and, consequently, before they had had time to 

 ovi]^osit. I dissected several, and in all cases found the ovary only 

 partially developed. Two specimens contained 26 eggs each, most of 

 which were more than half groAvn." 



Following upon the excessive rains on 1917, our fields were flooded 

 and I found many apparently lifeless grul)s lying about in the water 

 on the surface of the soil. This at once appealed to me as a possible 

 important ineans of control. Aluch to my surprise, however, I found 

 that these apparently drowned grubs soon revived when taken out of 

 water. I then followed this up with brief experiments to see how long 

 it was possible for the grubs to resist submergence. Though these 

 experiments were not extensive enough to be conclusive, I found that 

 the grubs ceased all noticeable activities after being in the water for 

 about fifteen minutes, though I was rather discouraged to learn that it 

 took approximately four days to kill tbem by drowning. 



Recently, at my suggestion, Mr. Dodd made the following very 

 careful check on these experiments: — On 29th March, 1921^ fifty pots 

 were prepared with soil, and each supplied with a healthy stage III grub 

 of Lepidoderma alholiirtum \ after the grubs had entered the soil, at 

 2 p.m. the pots were filled with water so that it was an inch deep over the 

 surface. At 2.30 p.m., 80th March, the grubs Avere taken out of ten of 

 the pots and placed in moist soil ; they were all rigid and motionless, and 

 appeared to be full of water. At 3.30 p.m. seven were moving. The' 

 next morning these had l)urrowed into the soil and Avere perfectly normal,, 

 while the other three were dead and limp. 



At 1.30 p.m. 31st March, ten more were taken out of the water and 

 treated as before. At 2.10 p.m. three showed signs of life, and the others; 

 had lost their rigidity. At 3 p.m. eight Avere reviving, though none AA-ere 



