78 On the Potato Gruh of Tasmania. 



for the purpose, and whence they descend into the root itself, 

 when desiccation ensues. This theory is opposed to the 

 writer's experience. He has invariably found that the moth 

 attacks the root. The uppermost potatoes, those that are 

 nearest the surface, are of course most easily reached, nor is 

 it by any means a difficult matter for the insect to penetrate 

 to the depth of three or four inches when the soil is open, 

 uncompressed, or lumpy. Not a single case of an infected 

 stalk has been yet detected ; but constant and numberless 

 have been the instances in which, when uncovering the 

 potatoes at the depths just indicated, moths have been 

 dislodged, and flown uninjured away. 



Before the writer correctly understood the nature and 

 routine of the insect's tactics, and while he yet believed that 

 its grub form was the only one in which the depredations were 

 to be guarded against, he caused a crop of infected potatoes 

 to be dug up, and exposed for some days to the efiPects of the 

 atmosphere, thinking that the heat of the sun would put a 

 stop to the further ravages of the larva : but this turned out 

 to be a woeful mistake. The potatoes while lying thus 

 exposed in rows were again attacked by the insects, and so 

 insidious were their proceedings, that the damage had been 

 greatly increased before their presence was discovered. And 

 it is not unworthy of remark, that the underside of the 

 potato, or the side in contact with the ground, was invariably 

 the part that was selected by the moth for the deposit of the 

 ova. This was doubtless owing to the greater security that 

 the unexposed side of the potato afforded against the weather, 

 as well as against birds and predatory insects, than the upper 

 surface would have done ; and it was afterwards noted, that 

 the moths, when unengaged in laying eggs, were almost 

 always to be found beneath the clods of earth with which the 



