124 ANNUAL REPORT. 
color, and usually enveloped ina fine cottony matter of a bluish-white color. 
It has no honey tubes. 
The best mode of extermination is to uncover, as far as possible, the 
diseased roots and drench them with hot water. Mulching with unleached 
wood ashes isjalso good. 
The leaves of our plum trees are subject to the attacks of a darker-brown, 
smooth aphis,Jjwhich, when it appears in such numbers as it did last sum- 
mer, checks the growth of the tree, disfigures it and seriously impairs the 
quality of the fruit. I do not know that any artificial remedy has been tried 
upon it. Syringing with weak carbolic acid, whale-oil or soap-suds would: 
doubtless destroy the pest. 
Green Louse on House Plants. 
One of the plant-lice that gives most trouble, and probably attracts most. 
general attention, is the ‘‘ green louse” or ‘green fly,” so troublesome to 
window plants and hot-house plants, and often to roses planted out in the 
garden. 
The usual remedy is smoking with tobacco; but it has been discovered 
recently that dusting with the Persian Insect Powder, or syringing with a 
tea made from the leaves of the tomato plant, are complete remedies, and 
in some cases preferable to the use of tobacco. Dr. Hagen, of Harvard 
University, claims that drenching inf sted plants with water in which a 
little yeast has been dissolved will produce in the lice a fangoid disease that 
will soon exterminate them. These new remedies are simple, easily applieck 
and cannot possibly harm the plants experimented upon. 
Gall-Making Lice. 
One of the most interesting groups of the Aphididw is that containing the 
gall-making species. The punctures of one of these Colopha ulmicola cause 
peculiar excrescences on the leaves of young elm trees, which, from their 
form, have been called ‘‘ cockscomb elm-galls.” They are somewhat puffy,. 
and when opened, are found to be inhabited by large colonies of purple,. 
downy lice of all sizes. 
Two species (Pemphigus vagabundus and P. populi-monilis) infest the cot- 
tonwood, the former causing a large fruit-like gall on the twigs, and the 
latter a row of bead-like swellings on the leaves. Another species (P. rhois), 
produces a large fungus-like gall on the sumac; and_still another (P. populi- 
transversus, Riley,) forms a hard, roundish, nut-like gall on the leaf-stalk of 
the poplar. 
Natural Enemies. 
All plant-lice, in whatever situation they are found, have their natural 
enemies. Minute chalcis flies lay their eggs in their bodies, from which 
hatch maggots that feed upon their vitals and shelter under their distended 
skins. The fierce and active larve of the Lacewing fly destroy hundreds. 
in a minute, while the less active but no less greedy young of several 
small beetles, belonging to the family of Lady-birds, gulp down countless 
numbers. Many other predacious insects, as well as spiders and some 
small birds, seek them eargerly and make short work in dispatching them. 
