The author has been for several years carrying on investigations with a view of ascertaining the full annual life-history of Phorodon humuli, and especially with a view of settling the hitherto mooted question as to its winter life. The importance of the inquiry, from both the economic and scientific sides, is self-evident. The hop crop, in all parts of Europe where it is grown, and especially in England, annually suffers more or less from the ravages of this, its worst insect enemy, and in some years is a total failure. The same is true in North America, at least east of the Rocky Mountains, and last year the injuries of this Phorodon in the hop growing regions of the State of New York were so great that many hop yards were abandoned and have since been plowed up; while but ten per cent. of an average crop was harvested. From the purely scientific side, entomologists, notwithstanding the great interest attaching to the subject, have been divided in opinion as to the identity of specific relationship of the Hop Phorodon and one that occurs on Prunus, while the full annual cycle of the insect's life has remained a mystery.

After full and satisfactory investigations Prof. Riley has satisfied himself that, contrary to the prevailing impressions among hop-growers and previous investigators, the Hop Plant-louse does not hibernate under ground on the roots of the hop, nor in, on or about anything in the hop yard; but that, upon the advent of the first severe frosts, the hop plants and the hop yards are entirely cleared of the species in any form. He finds that all statements to the contrary in this country are based on misapprehension or mistaken identity of species, and expresses the belief (though admitting the possibility of variation in this respect in milder climates) that the same will be found to hold true in England, where hibernation on the hop root has been accepted by high authority. The positive statements made about eggs being laid in autumn, whether on roots or upon the vines left in cutting or which are carted away, are based on conjecture, and have been blindly copied without credit by one writer from another - a practice too common among second-hand writers on economic entomology.

The conjectures of some of the best students of Aphidology that Phorodon humuli had a form (mahaleb, Tonsc.) living on Prunus and that there was a consequent migration from one plant to the other, have been positively proved to be correct by direct colonizing from Prunus to Humulus and by continuous rearing from the original stem-mother hatched from the winter egg.

The observations have been made on growing plants and in vivaria at Washington and checked by others made simultaneously at hop yards at Richfield Springs. An incident is recorded as illustrating the effect of meteorological extremes upon Aphides. The extreme heat and dryness of July 17th and 18th killed every one of the insects under observation at Washington, entirely clearing the plants. The economic bearing of such excep tional phenomena is discussed, as also of the biologic observations made. The more important conclusions of the author from his studies so far made are summed up as follows:

1. Phorodon humuli hibernates in the winter egg state, which is fastened to the twigs of different varieties and species of Prunus, both wild and cultivated. The egg is difficult to detect, because it is covered with particles which resemble the bark in color and appearance.

2. The annual life-cycle is begun upon Prunus by the stem-mother which hatches from this winter egg.

3. Three parthenogenetic generations are produced upon Prunus, the third becoming winged and instinctively abandoning the Plum and migrating to Humulus. The habit of moving from plant to plant after giving birth to an individual, and thus scattering the germs of infection, is well marked in this winged generation.

4. During the development of the three plum-feeding generations the hop is always free, and subsequently, until the return migration, the Plum becomes more or less fully free from infection by this species.

5. A number of parthenogenetic wingless generations are produced on the hop (seven or the tenth from the stem. mother on Plum having been traced up to August 5th), and finally there is a return migration of winged females to the Plum in autumn.

6. Exact observations are not yet complete as to the full number of generations produced upon the Hop before the winged return migrat appears, and another month's careful watching and experiment is needed to fill this hiatus in the annual cycle as also to ascertain the exact number of generations produced in autumn on the Plum. From knowledge extant and previous general observation, the fact will probably prove to be as follows:

7. The tenth or eleventh generation will produce winged females, about the middle of August, which will deposit their young upon the Plum, and these will become the only sexed individuals of the year, the male winged and the female wingless, the latter after coition, consigning a few impregnated or winter eggs to the twigs.

8. At the date of writing (August 5th) the first females on Hop are still alive and breeding, having existed two months. There is, consequently, an increasing admixture of generations from the first on Hop until frost overtakes the species in all conditions and sweeps from the face of the earth all individuals alike, perpetuating in the egg state those only which reached the sexual condition on the Plum.

9. Each parthenogenetic female is capable of producing, on an average, one hundred young (the stem-mother probably being more prolific) at the rate of one to six, or an average of three per day, under favorable conditions. Each generation begins to breed about the eighth day after birth, so that the issue from a single individual easily runs up, in the course of the summer, to trillions. The number of leaves (700 hills, each with two poles and two vines) to an acre will not much exceed a million, so that the issue from a single stem-mother may blight hundreds of acres.

10. While meteorological conditions may materially affect the increase and power for injury of the species, these are far more truly predetermined and influenced by its natural enemies, many of which have been studied and will be described.

11. The slight colorational differences, as also the structural differences, including the variation in the cornides on head and basal joints of antennae, whether on Plum or Hop, are peculiarities of brood, and have no specific importance whatever.

12. The exact knowledge gained simplified the protection of the hop plant from Phorodon attack. Preventive measures should consist in destroying the insect on Plum in early spring, where the cultivation of this fruit is desired, and the extermination of the wild trees in the woods wherever the hop interest is paramount. Also in avoiding the introduction of the pest into new hop countries in the egg state upon Plum cuttings or scions Direct treatment is simplified by the fact that the careful grower is independent of slovenly neighbors, infection from one hop yard to another not taking place. Experiments still under way have shown that there are many effective remedies, and that the ordinary kerosene emulsion diluted with twenty-five parts of water and sprayed with the cy clone nozzle, or a soap made by boiling one pound of pure potash in three pints of fish oil and three gallons of water, and this dissolved in eight gallons of water, and sprayed in the same way, are thoroughly effectual remedies, and leave the plant uninjured. The former costs seventy-five cents, the latter thirty cents per acre, plus the time of two men for three hours, plus appliances.

The object of further experimentation now being carried on is to simplify and reduce the cost of these last to a minimum.

(Abstract of a paper read before the Society for the Promotion of Agricultural Science).

[It is a well understood general law that animal life increases in proportion to the amount of food at its command. Insects fond of one plant will rarely leave that plant for another, but thrive and increase on the abundance. But there is room for suspecting that the tastes of living creatures have considerable elasticity, and we should not be surprised if an insect bred to a Plum would not experiment on and take to another kind when the Plum was abolished. But on this we would prefer the views of Prof. Riley or other experienced entomologists. - Ed. G. M].