870 Agricultural Gazette of X.SAV. [Dec. 2, 1920. 



reception of the egg aii'ordiug it a safe and easy means of entry into the 

 bulb. At first the channels are almost indiscernible, but they gradually 

 grow wider as the grub matures. On attaining maturity the grub usually 

 makes its way towards the surface of the bulb where the channel, which is 

 partially filled with sawdust-like particles of rejected banana tissue, ter- 

 minates in an oval chamber prepared by the grub. In this chamber the 

 grub undergoes its final moult and transforms to the pupal condition. Xo 

 true cocoon is formed as in the case of the sugar-cane beetle- (lihahdocnemis 

 ohscura), but the presence of a few strands of banana fibre on the inside of 

 the pupal chamber and the plugging of the outer end of it with a roll or 

 pad of banana fibres (Plate II, Fig. 10) indicates that the cocoon-making 

 habit has been largely lost. 



On emerging from the pupa the beetle, which is at first reddish-brown in 

 colour, does not immediately leave the pupal chamber, but remains until its 

 tissues have hardened up, its colour in the meanwhile gradually becoming- 

 darker and darker. The adult males and females are much alike, but can 

 be distinguished by the characters previously mentioned. 



With regard to the proportion of sexes, males predominate. Taking oue^ 

 hundred specimens haphazardly' in a plantation, I found fifty-nine were 

 males and forty-one females, and this percentage was supported later in 

 the laboratory in the examination of a large series of specimens. 



With regard to the periods occupied in the various stages of the beetle 

 development, Jepson has found that the egg period lasts five to seven days, 

 the larval period about twenty days, and the pupal period six to eight 

 days. These have been approximately confirmed by Moznette. My experi- 

 ments indicate, however, that the periods are more prolonged, more 

 particularly in the egg-stage, which I invariably found to be nine or ten 

 da.vs. The difference may be accounted for by the sub-tropical conditions 

 under which my observations were carried out, but further observations 

 are being made, pending which definite statements may be withheld. 



Seasonal History. 



Xornially the insects pass through the winter in the adult stage, but 

 some grubs are also found in the bulbs throughout the colder period. These 

 grubs are from eggs that were laid late in the autumn, and the grubs, 

 developing during the winter, are full grown in September, when they 

 pupate and emerge. The majority of the grubs, however, have changed to 

 beetles by the end of autumn and pass the winter as adults. 



In captivity no eggs were laid from May to September. Examination of 

 the ovaries throughout the winter revealed no egg development, but early 

 in September some well-developed eggs were found on dissection. The 

 beetles began to deposit eggs late in September. The conditions under 

 which the eggs were laid in captivity were as near as possible to those 

 experienced under natural conditions. It seems, therefore, that in the 

 Tweed Kiver district the first eggs after the winter are laid in September, 

 and that egg-laying is continued througliout the following months up to 

 April. 



