20 
A NEW TOBACCO PEST. 
m bis continued observations went, the insect was causing in its 
caterpillar or grub condition tbe destruction of hundreds of tons 
of potatoes every year, and that during late years he had scarcely 
been able to get half-a-dozen pounds without finding a consider- 
able percentage more or less affected by it. But it is not neces- 
sary to go beyond the colony of Queensland for evidence of the 
immense loss which the potato grub occasions. In the early 
part of the present year the potatoes which arrived from the 
Southern markets were to a large extent worm-eaten or ahready 
rotten, as every housewife must needs have observed — and here 
also, the pest was in evidence. As already pointed out by me, 
this formidable pest is not only conveyed from place to place in 
the tuber itself, but is also transmitted whilst still adherent to 
the sacks or other receptacles which have contained affected 
potatoes. 
At first its attention here was confined to the contents of 
the storeroom, and even as late as 1889 no instance of itg 
attacking the growing crop in Queensland had come under my 
notice, though it was suspected to be enacting this role ; but it 
had been already ascertained that wherever it occurred here it 
soon visited such of the tubers as had been unearthed. How- 
ever, in December of the following year — 1890 — on visiting a 
cultivation in the district of Moggill, near Brisbane, a patch of 
still growing plants was found to be affected by the presence of 
the pest, and, in fact, was in rapid process of destruction. An 
important trait in the habit of the insect which has not been 
remarked by any previous writer was observed on the occasion of 
this visit. It being noticed that the larva of the moth was not 
confining its attention to the tubers but was also mining in the 
tissue of the leaves, on which it occasioned a brown spotted 
appearance. This interesting feature in the habits of Lita solan- 
ella was not, however, observed with surprise, since an example 
of the perfect insect had been previously reared by me in a 
potato leaf forwarded from Toowoomba. The chief interest, 
however, in this communication resides in what is to follow. 
Insects are better judges of botanical affinities between 
plants than are, in many instances, ourselves. The cabbage 
worm, Plutella cruciferarum, which we know too well, recognises 
