gnats, are very active, and, though very small and seemingly feeble, are able to fly to a considerable distance in search of fields of young grain. Their principal migrations take place in August and September in the Middle States, where they undergo their final transformations earlier than in New England. There, too, they sometimes take wing in immense swarms, and, being probably aided by the wind, are not stopped in their course either by mountains or rivers. On their first appearance in Pennsylvania they were seen to pass the Delaware like a cloud. Being attracted by light, they have been known, during the wheat harvest, to enter houses in the evening in such numbers as seriously to annoy the inhabitants.*

The old discussion, concerning the place where the Hessian fly lays her eggs, has lately been revived, in consequence of a communication made by Miss Margaretta H. Morris, of Germantown, Pennsylvania, to "the American Philosophical Society," of Philadelphia. The following remarks upon it are extracted from a Report made to the same Society, and published in their "Proceedings " for November and December, 1840. "Miss Morris believes she has established that the ovum (egg) of this destructive insect is deposited in the seed of the wheat, and not in the stalk or culm. She has watched the progress of the animal since June, 1836, and has satisfied herself that she has frequently seen the larva within the seed. She has also detected the larva, at various stages of its progress, from the seed to between the body of the stalk and the sheath of the leaves. According to her observations, the recently hatched larva penetrates to the centre of the straw, where it may be found of a pale greenish white semitransparent appearance, in form somewhat resembling a silk worm. From one to six of these have been found at various heights from the seed to the third joint." Miss Morris's communication has not yet been published in full; but, from the foregoing report, we are led to infer, that the egg, being sowed with the grain, is hatched in the ground, and that the maggot afterwards mounts from the seed through the

British and Dobson's "Encyclopædia," and Colonel Morgan's letter in Carey's "American Museum," Vol. II., p. 298.

middle of the stem, and, having reached a proper height, escapes from the hollow of the straw to the outside, where it takes the pupa or flax-seed state. The fact that the Hessian fly does ordinarily lay her eggs on the young leaves of wheat, barley, and rye, both in the spring and in the autumn, is too well authenticated to admit of any doubt. If, therefore, the observations of Miss Morris are found to be equally correct, they will serve to show, still more than the foregoing history, how variable and extraordinary is the economy of this insect, and how great are the resources wherewith it is provided for the continuation of its kind.

Various means have been recommended for preventing or lessening the ravages of the Hessian fly; but they have hitherto failed, either because they have not been adapted to the end in view, or because they have not been universally adopted; and it appears doubtful, whether any of them will ever entirely exterminate the insect. It is stated in the before mentioned Report of "the Philosophical Society," that Miss Morris advises obtaining "fresh seed from localities in which the fly has not made its appearance," and that "by this means the crop of the following year will be uninjured; but in order to avoid the introduction of straggling insects of the kind from adjacent fields, it is requisite that a whole neighbourhood should persevere in this precaution for two or more years in succession." "This result," Miss Morris says, "was obtained, in part, in the course of trials made by Mr. Kirk, of Buck's County, Pennsylvania, with some seedwheat from the Mediterranean, in and since the year 1837. His first crop was free from the fly; but it was gradually introduced from adjacent fields, and, in the present year (1840), the mischief has been considerable." In other hands this course has proved of no use whatever. Not to mention other instances, the following appears to be conclusive on this point. About forty years ago, Mr. Garret Bergen, of Brooklyn, New York, procured two bushels of wheat from the Genesee country, then an uninfected district, which he sowed in a field adjoining a piece seeded with grain of his own gathering. Both pieces were severely damaged by the Hessian fly, which could not have happened, in the same season, if the eggs of the insect are laid only on the grain. A few years ago he soaked his seed-wheat in

strong pickle, and the crop was comparatively free from the fly. In 1839 he tried this experiment again, but not with similar success. In 1840 he sowed without previously soaking the grain, and his crop was uninjured. He says, moreover, that he has uniformly found the grain most affected in spots, usually near the edges of the field, where long grass and weeds grew, which afforded shelter and protection to the fly. This fact, he thinks, affords another proof, that the egg is not deposited in the grain. I regret that my limits will not permit me to extract the whole of Mr. Bergen's interesting remarks, which may be found in number eight, of the eighth volume of "The Cultivator," published in Albany in August, 1841. The best modes of preventing the ravages of the Hessian fly are thus stated by Mr. Herrick.* "The stouter varieties of wheat ought always to be chosen, and the land should be kept in good condition. If fall wheat is sown late, some of the eggs will be avoided, but risk of winter-killing the plants will be incurred. If cattle are permitted to graze the wheat fields during the fall, they will devour many of the eggs. A large number of the pupa may be destroyed by burning the wheat-stubble immediately after harvest, and then ploughing and harrowing the land. This method will undoubtedly do much good. As the Hessian fly also lays its eggs, to some extent, on rye and barley, these crops should be treated in a similar manner." It is found that luxuriant crops more often escape injury than those that are thin and light. Steeping the grain and rolling it in plaster or lime tends to promote a rapid and vigorous growth, and will therefore prove beneficial. Sowing the fields with wood ashes, in the proportion of two bushels to an acre, in the autumn, and again in the first and last weeks in April, and as late in the month of May as the sower can pass over the wheat without injury to it, has been found useful.† Favorable reports have been made upon the practice of allowing sheep to feed off the crop late in the autumn, and it has also been recommended to turn them into the fields again in the spring, in order to retard the growth of the plant till after the fly has disappeared.

"American Journal of Science," Vol. XLI., p. 158.

"Cultivator," Vol. V., p. 59.

"Cultivator," Vol. IV., p. 110, and Vol. V., p. 49.

Too

much cannot be said in favor of a judicious management of the soil, feeding off the crop by cattle in the autumn, and burning the stubble after harvest; a proper and general attention to which will materially lessen the evils arising from the depredations of this noxious insect.

*

Fortunately our efforts will be aided by a host of parasitical insects, which are found to prey upon the eggs, the larvæ, and the pupae of the Hessian fly. Mr. Herrick states, that, in this part of the country, a very large proportion, probably more than nine tenths, of every generation of this fly is thus destroyed. One of these parasites was made known by Mr. Say, in the first volume of the "Journal of the Academy of Natural Sciences of Philadelphia"; and the interesting discovery of three more kinds is due to the exertions of Mr. Herrick. They are all minute Hymenopterous insects, similar in their habits to the true Ichneumon-flies. The chief parasite of the pupa is the Eurytoma destructor (Ceraphron destructor, of Say), a shining black fourwinged fly, about one tenth of an inch in length. This has often been mistaken for the Hessian fly, from being seen in wheatfields, in vast numbers, and from its being found to come out of the dried larva skin of that fly. In the month of June, when the maggot of the Hessian fly has taken the form of a flax-seed, the Eurytoma pierces it, through the sheath of the leaf, and lays an egg in the minute hole thus made. From this egg is hatched a little maggot, which devours the pupa of the Hessian fly, and then changes to a chrysalis within the shell of the latter, through which it finally eats its way, after being transformed to a fly. This last change takes place both in the autumn and in the following spring. Some of the females of this or of a closely allied species of Eurytoma come forth from the shells of the Hessian fly, without wings, or with only very short and imperfect wings, in which form they somewhat resemble minute ants. Two more parasites, which Mr. Herrick has not yet described, also destroy the Hessian fly, while the latter is in the pupa or flax-seed state. Mr. Herrick says, that the egg-parasite of the Hessian fly is a species of Platygaster, that it is very abundant in the autumn,

"American Journal of Science," Vol. XLI., թ. 156.

when it lays its own eggs, four or five together, in a single egg of the Hessian fly. This, it appears, does not prevent the latter from hatching, but the maggot of the Hessian fly is unable to go through its transformation, and dies after taking the flax-seed form. Meanwhile its intestine foes are hatched, come to their growth, spin themselves little brownish cocoons within the skin of their victim, and, in due time, are changed to winged insects, and eat their way out. Such are some of the natural means, provided by a benevolent Providence, to check the ravages of the destructive Hessian fly. If we are humiliated by the reflection, that the Author of the universe should have made even small and feeble insects the instruments of His power, and that He should occasionally permit them to become the scourges of our race, ought we not to admire His wisdom in the formation of the still more humble agents that are appointed to arrest the work of destruction.

In the years 1829 and 1830 several communications were published in the eighth volume of Fessenden's "New England Farmer," respecting a disease of barley straw, produced by the punctures of insects. The first account of this disease, that has fallen under my notice, is contained in an extract from a letter, dated August 16th, 1829, from the Honorable John Merrill, of Newburyport, to Mr. Fessenden; wherein it is stated, that the barley, in the neighbourhood of Newburyport, yielded only a very small crop; on some farms not much more than the seed sown. Most of the stalks were found to have a number of small worms within them, near to the second joint, and had become hardened in the part attacked, from the interruption of the circulation of the sap. During several years previous to this date, the barley crops, in various parts of Essex and Middlesex counties, were more or less injured in the same way; and, in some places, the cultivation of this grain was given up in consequence thereof. It was supposed that the insects, producing this disease, were imported from Bremen, or some other port in the north of Europe, in some barley that was sown in the vicinity of Newbury, three or four years before 1829.† The worms or

*

Pages 43, 138, 217, 299, 330, and 402. Also Vol. IX., p. 2, and Vol. X., p. 11. t “New England Farmer,” Vol. VIII., p. 217.