24 AUSTEALTAN SUGAE-CANE BEETLES AND THEIE ALLIES. 



shows an egg just laid; fig. 5, one week after; and fig. 6, when a fortnight 

 old, ready to hatch. A better notion perhaps of the fresh egg. in 

 natural size and colour, is show^n on Plate 1, fig. 2. 



The incubation period, as indicated above, is evidently considerably 

 affected by unfavourable conditions, such as extremes of temperature, 

 moisture, &c. We have seen, however, that the parent beetle seeks to 

 avoid such extremes by placing the eggs very deep in the soil. Yet it is 

 hardly possible to follow their development closely in these natural 

 conditions. 



Nevertheless, with experimicnts carried on in the open-air insectary, 

 under conditions as nearly normal as possible, we found the duration of 

 this stage to be fourteen to sixteeii days, which probably is not very 

 different from results in the field. At any rate I think we are not far 

 out of the way in estimating a fortniglit for the egg stage under field 

 conditions. 



The Grill) or Larva. — On 15th January. 1921, I was fortunate in 

 observing the hatching of the eggs. AVlien I tipped them out of the pot 

 most of the grubs had already escaped, but several were still in the act 

 of eating their way out. One had evidently just escaped, for its head 

 w^as white and soft, and it had already eaten half of its shell. oMoreover, 

 since there were no other eggshells in the soil, it would appear that 

 the grubs invariably make their first meal upon this waste material, 

 immediately after hatching, as is often the case with other insects. 



The grubs pass through three distinct larval stages, direct evidence 

 of which was obtained by Girault and Dodd {i!>&) by rearing. I under- 

 stand that the first author published minute technical descriptions of 

 these stages in "Societas Entomologica," Germany, 1913, but I have not 

 been able to refer to it. 



The newly hatched grubs at once begin to Avork their way upward, 

 and shortly they are found near the surface among the cane-roots, where 

 they remain during the whole of the growing period if the weather 

 remains favourable. Under dry conditions, however, they burrow deeper ; 

 but during an over-supply of moisture, on the other hand, they work 

 nearer the surface, in fact coming riglit out of the soil, where trash and 

 other vegetable matter is available for them to feed upon and hide under. 

 Particular attention was called to this latter habit by ^Ir. J. Clark (35) 

 at Hambledon, where it was made use of extensively for the collection 

 of the grubs during rainy weather. He mentions one grower, Mr. W. C. 

 Abbott, who collected about 100 gallons of grubs during the season from 

 two acres of Badila, by simply picking them from under the piles of 

 trash during the wet weather. 



To determine the duration of each of the stages through Avhich the 

 grubs pass, Girault and Dodd (66) reared them in soil planted to corn 

 at the laboratory, and successfully carried a few of them through all 

 of the stages. From their results it would appear that the first and 

 second stages recpiire about five to six weeks each, and the third stage 

 three to four months. 



Under the splendid growing conditions in the soil at Greenhills, 

 our field observations indicate that the grubs are much more rapid in 

 their development. The season of 1920-21, being a normal one, may be 

 used for purpose of illustration. On 31st December, 1920, we dug up 

 the first stage I grubs in the field, and they appeared to be a fortnight 



