It is somewhat remarkable that the true nature of this covering of the maggot should not have been ascertained by English naturalists. Mr. Kirby, as before stated, supposed it to be a thin membrane, formed by the insect for the protection of its body from the cold of winter. According to Professor Henslow's account, the larvæ "spin themselves up in a very thin and transparent web, which is often attached to a sound grain, or to the inside of one of the chaff-scales." Mr. Curtis observed on the backs of some of the shrivelled grains "a long narrow filmy sac, on opening which a bright orange granulated maggot came out alive; and when shut up in a tin box, many voluntarily left their cases and wandered about."† Having carefully watched the insect during the moulting period, I am convinced that what these gentlemen called a "membrane," "web," or "sac," is really the loosened outer skin of the maggot, which is subsequently thrown off in the ears of the wheat, or is cast upon the surface of the ground. After shedding its skin, the maggot recovers its activity, and writhes about as at first, but takes no food. It is shorter, somewhat flattened, and more obtuse than before, and is of a deeper yellow color, with an oblong greenish spot in the middle of the body. Within two or three days after moulting, the maggots either descend of their own accord, or are shaken out of the ears by the wind, and fall to the ground. They do not let themselves down by threads, for they are not able to spin. Nearly all of them disappear before the middle of August; and the very rarely found in the grain at the time of ha Gago stated, in one of her letters, that she served how and when the insects issue fr but that it was "apparent they go in comp haps they crawl out upon the heads du are washed down to the ground, where the Journal of the Royal Agricultural Society of T ot infallible, or every acre slacked lime 1 this should wet with dew ave sometimes gots after they selves to their the ground, redvised ploughing rvested, in order deeply that they formed to flies. I ng will prove to be Perhaps thoroughly may contribute to the dust, and refuse straw found to contain any ly burnt. It is stated injury by sowing early ..By the first, it is suphard before many of the by the latter, the plants the flies have disappeared. 1 where these insects have cultivation of fall-sown or p; and this, for some years st course. The proper time Il vary with the latitude and the forwardness of the season. made in this part of the counn after the 15th or 20th of May ges of these destructive insects. entirely banished the wheat-flies culture of Massachusetts, p. 67. transformations. Moreover, the pupa is entirely naked, not being enclosed either in a cocoon or in the puparium formed of this outer skin of the larva, and it has its limbs and wings free or unconfined. The pupa state lasts but a short time, a week or two at most, and probably, in many cases, only a few days. Under the most favorable circumstances, the pupa works its way to the surface, before liberating the included fly; and when the insect has taken wing, its empty pupa-skin will be seen sticking out of the ground. In other cases, the fly issues from its pupa-skin in the earth, and comes to the surface with flabby wings, which soon expand and dry on exposure to the air. This last change occurs mostly during the months of June and July, when great numbers of the flies have been seen, apparently coming from the ground, in fields where grain was raised the year before. Some persons have stated that the insects are transformed to flies in the ears of the grain, having probably mistaken the cast-skins of the maggots found therein for the shells of the chrysalis or pupa. Several cases of the efficacy of fumigation in preventing the depredations of these insects are recorded in our agricultural papers.* For this purpose brimstone has been used, in the proportion of one pound to every bushel of seed sown. Strips of woollen cloth, dipped in melted brimstone, and fastened to sticks in different parts of the field, and particularly on the windward side, are set on fire, for several evenings in succession, at the time when the grain is in blossom; the smoke and fumes thus penetrate the standing grain, and prove very offensive or destructive to the flies, which are laying their eggs. A thick smoke from heaps of burning weeds, sprinkled with brimstone, around the sides of the field, has also been recommended. Lime or ashes, strown over the grain when in blossom, has, in some cases, appeared to protect the crop; and the Rev. Henry Colman, the Commissioner for the Agricultural Survey of * Among others, see The Cultivator, Vol. V. p. 136. Massachusetts, says that this preventive, if not infallible, may be relied on with strong confidence.* For every acre of grain, from one peck to a bushel of newly slacked lime or of good wood-ashes will be required; and this should be scattered over the plants when they are wet with dew or rain. Two or three applications of it have sometimes been found necessary. Whether it be possible to destroy the maggots after they have left the grain, and have betaken themselves to their winter quarters, just below the surface of the ground, remains to be proved. Some persons have advised ploughing up the ground, soon after the grain is harvested, in order to kill the maggots, or to bury them so deeply that they could not make their escape when transformed to flies. I am inclined to think that deep ploughing will prove to be the best and most practicable remedy. Perhaps thoroughly liming the soil before it is ploughed may contribute to the destruction of the insects. The chaff, dust, and refuse straw should be carefully examined, and, if found to contain any of the maggots, should be immediately burnt. It is stated that our crops may be saved from injury by sowing early in the autumn or late in the spring. By the first, it is supposed that the grain will become hard before many of the flies make their appearance; and by the latter, the plants will not come into blossom until the flies have disappeared. In those parts of New England where these insects have done the greatest injury, the cultivation of fall-sown or winter grain has been given up; and this, for some years to come, will be found the safest course. The proper time for sowing in the spring will vary with the latitude and elevation of the place, and the forwardness of the season. From numerous observations made in this part of the country, it appears that grain sown after the 15th or 20th of May generally escapes the ravages of these destructive insects. Late sowing has almost entirely banished the wheat-flies *Third Report on the Agriculture of Massachusetts, p. 67. from those parts of Vermont where they first appeared; and there is good reason to expect that these depredators will be completely starved out and exterminated, when the means above recommended have been generally adopted and persevered in for several years in succession. * In the introductory chapter a short account has already been given of the habits of the various kinds of gnats and flies, belonging to the principal families of this order. Besides the species that are injurious to vegetation, which have been now described, there still remain some of our native flies that deserve a passing notice, on account of their size, or of peculiarities in their forms, structure, and habits, although few of them are to be included among the insects which are hurtful to plants. Among our long-legged gnats there is no one more singular in its appearance and graceful in its motions than the Ptychoptera clavipes of Fabricius, or club-footed Ptychoptera. A new genus, called Bittacomorpha, on account of the fancied resemblance of this insect to the Neuropterous genus Bittacus, has lately been made for its reception, by Mr. Westwood. This pretty gnat is of a black color, with a broad, white stripe on the face, a short, white line on the fore part of the thorax, and three broad, white rings on the legs. The sides of the thorax are silvery white, and the hind body is dusky brown, with a narrow white line on the edges of each of the rings. The head is small, and almost hidden under the thick and hunched thorax; the antennæ are manyjointed, slender, and tapering; the hind body is long, narrow, and somewhat flattened; the legs are very slender next to the body, and increase in thickness towards the end, and the first joint of the feet is swollen, oblong oval, and very downy. The length of the body is about half an inch, and the wings expand nearly three quarters of an inch. It appears in July, and takes wing by day. As it flies slowly *Pages 16 and 17. † Philosophical Magazine, Vol. VI. p. 281.. Lond. 1835. |