“In the neighbourhood of my native place (in the county of York),” says the writer, Mr. T. Clithero, “is a rookery belonging to W. Vavasour, Esq., of Weston, in Wharfdale, in which it is estimated that there are 10,000 rooks; that 1 lb. of food a week is a very moderate allowance for each bird, and that nine-tenths of their food consists of worms, insects, and their larvæ; for, although they do considerable damage to the fields for a few weeks in seed-time, and a few weeks in harvest, particularly in backward seasons, yet a very large proportion of their food, even at these seasons, consists of insects and worms, which (if we except a few acorns and walnuts in autumn) compose at all other times the whole of their subsistence. Here, then, if my data[197] be correct, there is the enormous quantity of 468,000 lb., or 209 tons, of worms, insects, and their larvæ, destroyed by the rooks of a single rookery in one year. To everyone who knows how very destructive to vegetation are the larvæ of the tribes of insects, as well as worms, fed upon by rooks, some slight idea may be formed of the devastation which rooks are the means of preventing.”
Let this, then, suffice for the rooks; but starlings, wagtails, larks, and other birds, are also helpmates to the farmer; and therefore the wanton destruction of these will certainly bring, nay, has already brought, a great amount of trouble upon the cultivator of the soil.
The destruction we speak of has been committed by clubs and societies established for the purpose; but, as their members are mostly filled up with all sorts of prejudices—few being naturalists, or even accurate observers—it becomes daily a matter of more pressing importance that middle-class education, if not National-school teaching, should recognise the value of the natural sciences.
2. The Gout-fly (Chlorops glabra) and the Saw-fly (Sirex pygmæus) both lay their eggs below the first node or knot of the young plant, which, as soon as they hatch, form maggots that eat out the substance of the stems and the nodes, which thus become weakened and ultimately break off, or, if left standing, the ears of corn as they appear will be dried, whitened, and infertile.
In these, as in most cases of insect attacks, we have an occasional blight of such extent as to destroy whole crops, against which we are almost powerless, as we know so little of the economy of the creatures by whom the mischief is caused; still, there can be little doubt but that their periodical appearance, to the extent to cause them to be recognised as blights, is due to the thinning of their enemies; and we have always observed that a paucity of the Hirundines—the swallow tribe of birds, their greatest enemies—is coupled with a great increase of the smaller insects which it is the vocation of swallows, bats, and others of the hawking insectivorous creatures, to take on the wing.
3. The Wheat-midge (Cecidomyia tritici), also called the Hessian-fly, is sometimes very destructive to the wheat crop. In 1860 we observed the effects of this creature to a greater extent than we have before known, in not a few instances rendering the crop scarcely worth reaping. Upon this creature we sent the following notice to the Agricultural Gazette for August 30, 1862:—
The wheat-midge (Cecidomyia tritici) has been so destructive for the last two or three years, that every fact connected with its history ought to be of great interest. Curtis tells us that “in Scotland one-third of the crop was lost, and the farmers suffered severely in 1828 and the three following years;” whilst “in Suffolk the yield[19] of wheat was one-third less in some districts in 1841 than was expected.”
The presence or absence of this insect is so important as affecting the yield, that we now never fail to look for it in every crop upon which we would offer a judgment in this respect.
It is easily detected in the larva state on opening some of the chaff-scales—pales—of affected crops, as in the interior of these will be found some minute larvæ (maggots) of a bright yellow or orange colour. In the earlier period of the blossom these larvæ will be found about the[199] stamens and pistils; later, upon the grain, which is always shrivelled and lost where the attack has been made.
The colour of the maggots is so much like that of the red-rust as often to be mistaken for it; the difference, however, between the bunches of minute granular fungi and living worms will be made apparent to the most careless observer by the assistance of a common pocket lens. We find two terms in use for these yellow appearances—namely, red-rust and red-gum; and as we have so often found them employed indiscriminately, we would restrict the former to the fungus,[20] thus—Uredo rubigo, red-rust; and Cecidomyia tritici, red-gum. Our observations on the latter this year have chiefly been made in the counties of Sussex and Gloucester, in both of which we have seen this insidious enemy at work to an alarming extent. In the former county, with a very limited extent of red-rust; in the latter, the later and more delicate wheats have both red-rust and red-gum in the same crop: and the interest of the subject will be the more forcibly apprehended when we say that in some crops, which, from a first glance at the straw and ears, we should have put down as somewhere about thirty bushels per acre, we have, after a more minute inspection of the ears, estimated at less than twenty bushels; and, indeed, in one field which we have examined during the last week (August, 1862), affected by the Cladosporium, Uredo, and Cecidomyia, there will scarcely be a yield in good grains of the amount of the seed sown.
[19] We believe this creature to be one of the most common causes of deficient yield, so that a knowledge of its history is all-important in estimating the value of a crop, which, as a rule, we should always put lower in the seasons when this blight abounds.
The fly which lays the eggs from which these yellow larvæ are derived is of about the size of a gnat, and usually takes the wing in the evening, in which case, if its enemies the bats are not numerous, smother fires lighted towards sundown on the wind side of the fields are not only destructive to large numbers, but act as an offensive notice to quit to others. Curtis says:—