232 HEMIPTERA. 
It was first observed by Dr. Plumb in the spring of 1833, 
on some imported pear-trees, which had been set the year 
before. These trees, in the autumn after they were planted, 
wore an unhealthy aspect, and had patches of a blackish 
rust upon their branches. During the second summer, these 
trees died ; and other trees, upon which the same rusty 
matter was found, proved to be infested with the same 
insects. 
Like the aphides, or plant-lice, these insects live by suc- 
tion. By means of their suckers, which come from the 
lower side of the head near the breast, they puncture the 
bark of the twigs and small branches, and imbibe the sap. 
They soon gorge themselves to such a degree, that the fluid 
issues constantly from their bodies in drops, is thrown over 
the surface of the twigs, and, mingled with their more solid 
castings, defiles the bark, and gives it the blackish color 
above noticed. Swarms of flies and ants upon the trees are 
a sure indication of the presence of these sap-suckers, being 
attracted by the sweetish fluid thrown out by them. 
Young trees suffer excessively by the attacks of these in- 
sects, nor do old trees escape without injury from them. In 
consequence apparently of their ravages alone, Dr. Plumb 
lost several hundred pear-trees from 1834 to 1838 inclusive ; 
his trees have continued to suffer, to some extent, from this 
cause, since that time ; and he informs me that the same 
destructive depredations have been observed in all the ad- 
jacent region. On the 23d of July, I saw these insects 
on the trees, some already provided with wings, and others 
advancing towards maturity. The young ones were of a 
dull orange-yellow color. They were short, and were ob- 
tuse behind, and had little wing-scales on the sides of their 
bodies. The perfect, or winged individuals, were about one 
tenth of an inch long from the forehead to the tips of flic 
closed wings. The front of the head was notched in the 
middle. The eyes were large and prominent. The head 
and thorax .were brownish orange, and the hind body green- 
