On the Potato Grub of Tasmania. 77 



of the potato, or other convenient indentation of its surface, 

 and protected hy a cocoon of very flimsy and inartificial 

 construction. 



What may be the usual period that the ova lie unhatched, 

 it would perhaps be assuming too much to assert on the 

 strength of only a couple of experiments. It is probable 

 that the time varies with the temperature^ with the position 

 of deposit, and perhaps also with other concurrent circum- 

 stances. All that can be confidently made known is this, 

 that in the experiments, which were conducted under the eye 

 of the writer of these notes, the time that elapsed between 

 the laying and the hatching of the eggs was ten days. 



The existence of the larvae, from their birth to their trans- 

 formation into pupse, is of about a fortnight or three weeks' 

 duration. Their voracity, however, is so great, and their 

 diligence in their vocation so untiring, that a couple of 

 individuals will thoroughly riddle and destroy a potato of 

 fair size during their brief but mischievous career. 



The pupa state, it is to be presumed, as in the case of 

 other Lepidopterous insects, extends over a period of some 

 months, and it were vain, therefore, on the part of the writer, 

 to expect that any further transformation will take place in 

 the specimens which he has preserved until the revolution 

 of the seasons shall have brought round the appointed time 

 of revival. The moth itself lives but a few days, and the 

 deposit of its ova is speedily followed by death. 



Under the supposition that the root of the potato is 

 unapproachable, and safe from the attacks of the insect, it 

 has been surmised by some that the moth deposits its eggs 

 on the stalk of the plant, whence the larvse continue to draw 

 their nourishment as long as it remains sufficiently succulent 



