130 
and quince trees, causing the tender leaves and the young shoots 
and twigs to turn black, as though they had been burned by fire. 
On old trees it is not so common, though it frequently congregates 
on such as are in bearing, and causes the young fruit to wither 
and drop.” His remarks on a supposed connection between the 
punctures of this insect and the potato-rot, have been already 
quoted. 
It will be remembered, however, that Mr. Wier, who had a much 
more extended experience with this insect than the gentlemen just 
quoted, saw no evidence of any other injury to the plant than that 
naturally to be explained by the abstraction of sap from young and 
erowing structures, and I may add that there was nothing whatever, 
either in the appearance of the buttoned strawberries, or in the 
cell-contents of the injured parts, to indicate that they were suffer- 
ing from any other than a mechanical injury. It would require, in 
fact, the very strongest evidence to warrant a belief in so extraordi- 
nary a phenomenon. 
It is contrary to the order of nature that a habit of this. sort 
should be acquired, unless it were beneficial, directly or indirectly, 
to the species acquiring it. It is not only impossible to show that 
the plant bug would be benefited by any such supposed poison- 
ing of its own food, but it is at once evident that it would be 
seriously injured thereby, since this would amount to the prompt 
destruction of the very parts of the plant from which it was draw- 
ing its own food supply. 
Assuming, as we doubtless should do, the correctness of the obser- 
vations reported both by Harris and by Riley, we may easily explain 
them without violence to probability, by the supposition of the 
coincidence of the potato-rot in one case, and in the other, of one of 
the common blights of fruit trees, with the presence of these insects 
upon the foliage. Indeed, with respect to the pear-blight, at least, 
it is not at all impossible that the plant bug may convey the con- 
tagion from one tree to another, since it has now been fairly well 
proven that this disease is spread by means of a microscopic virus 
coutained in the sap of affected parts. 
NATURAL ENEMIES. 
There are few species of really destructive insects which seem so 
free from natural checks upon their increase, as this plant bug. In 
fact, with the exception of the injurious effect produced upon its 
rate of multiplication by extraordinary wet weather, (a trait which 
it shares with a great variety of other insects), no destructive nat- 
ural agent has yet been reported, and none worth serious considera- 
tion has come under my own observation. It is free, as far as we 
know, from the attentions of either plant or insect parasite; and, 
while it has no apparent protection against the depredations of birds, 
yet they do not seem to prey upon it to any important extent. 
In the food of three hundred and fifteen robins, cat-birds, and 
other thrushes, taken at all seasons of the year, and carefully 
i 
