=Aphis cerasi=, (_Fabric._), or the Cherry Plant-louse, is very common, very numerous, and very black. They appear with the first expansion of the leaves, and continue or are renewed when destroyed, and remain until mid-summer, when they generally disappear. Their numbers are almost incredible, and they give a young cherry tree a wretched appearance. On the under surface of a small leaf, three-fourths of an inch long, Mr. Fitch counted one hundred and ninety lice, on one side only of the midrib. Their natural enemies come to the rescue to check their wonderful increase, and sometimes will utterly rout the _Aphides_ in a single week.[32] The remedies advised for the apple tree _Aphides_, are equally applicable to those of the cherry, and their natural enemies are the same and equally efficacious; but _Aphides_ have internal foes likewise, that may be named here. The Ichneumon-flies are parasitic, their larvæ feed upon the substance of the _Aphides_. The genus _Aphidius_ is particularly provided to furnish parasites to these insects, in which they deposit a single egg selecting a louse of the proper size to sustain their progeny: the egg hatches to a larva, which exhausts the _Aphis_ by the time it has attained its growth, when the poor creature fastens itself securely to the leaf, and dies, leaving its carcase a secure resting place for the pupa of the Ichneumon. These parasitic-insects, which feed internally upon the _Aphides_, are as effective in their destruction as the Aphis-lions, or any other class of their enemies.[33] =Aphis persicæ=, or the Peach Tree-louse, punctures the leaves of this plant, and Dr. Fitch[34] thinks, is the common though not the only cause of the curl in the peach tree leaves. Our intelligent orchardists have found these insects occasionally in the curled leaves of the peach, but do not agree with this distinguished entomologist, in considering them a cause of that malady. =Aphis vitis?=, or the Vine _Aphis_, is often quite troublesome on vigorous young shoots of the grape vine, both wild and cultivated, particularly the former. These insects soon cripple the growth of the shoot. The species is not known to be different from that of Europe. This insect is briefly mentioned by T. Glover, in Patent Office Rept. for 1854, p. 79. Dr. Fitch describes as a grape leaf-louse, the _Pemphigus vitifolia_, which inhabits the gall-like excrescences upon the foliage of some varieties, particularly those with thin leaves. =Aphis ribis=, (_Linn._), is the _Aphis_ of the currant. It causes the leaves to present a blistered appearance above; the lice are found on the under side; the wingless are pale yellow, the others have glossy wings, mostly black, with abdomen light green.[35]