Phorodon Humuli
This insect, known also as the Hop Aphis, is frequently most destructive to the Hop-plants, where these are cultivated on a large scale; but in gardens it does little harm, though occasionally hurtful to Hops grown for ornamental purposes. It belongs to the green group of Aphides, and the genus differs very little from the other Green Flies in appearance. Many efforts have been made to combat this pest in the Hop-gardens. One remedy is to wash the plants thoroughly, with the help of a garden engine, with a solution of 3lb. or 4lb. of soft soap in 200 gallons of water, adding a little infusion of coarse tobacco to the solution if thought fit; another is furnished by a newly-discovered emulsion of petroleum, which is said to be very effective. In gardens, it is only necessary to look occasionally to the young shoots, and to crush the Aphides before they become numerous. What is regarded by most entomologists as a variety of this insect (P. Humuli, var. Mahaleb) occurs in gardens on leaves of Plums, and also lives on Sloes. Among the most useful assistants in reducing the ravages of these, as well as of other Aphides, are the larvae of Ladybirds (Coccinella septempunctata, &c.), of Golden-eyed Flies (Chrysopa); and of Hawkflies (Syrphus).