Part 23 (1/2)
1. The _Slug_ may be described as a houseless snail. There are several species, but the milky slug (_Limax agrestis_) and the black slug (_L.
ater_) are those most common to our corn crops, and are more especially mischievous to wheat; for, as this crop usually succeeds clover or ”seeds,” in which they breed most rapidly, so, the older the clover lea, the more eggs will be ready to hatch in the wheat crop, and this all the more readily as the wheat is nearly always put in with a single ploughing, and with as little cultivation as possible.
The best remedy will be found in encouraging insectivorous birds-the lark, rook, starling, peewit, and others, eating them either in the egg or young state with great avidity; a good a.s.sistance to whose labours may be supplied in a few broods of ducks from the farmyard, which it will pay well to have tended by a good boy-where such can be found-as these birds are most efficient as destroyers of slugs and caterpillars.
Store pigs turned into old leas, where they can do no mischief, will get no bad living where snails and insects abound.
_Wire-worms._-The several species of beetle which produce the wire-worm belong to the genus _Elater_. They are of a long oval shape: about half the length belongs to the head and thorax, and the other to the abdomen.
Every schoolboy knows that when he holds the insect on its back it elevates the abdominal portion, and again lets it fall so as to make a beating sound; and hence its generic name, and also its common name of click-and-hammer beetle. If he remove his finger when in this position, the creature immediately skips up and turns on its feet, from which action it has got the name of ”skipjack.”
Curtis has estimated nearly seventy species of click-beetles as producing wire-worms in this country; but the three following are those generally met with-_Elater lineatus_, _E. obscurus_, and _E.
ruficaudis_. These all attack corn and almost every other kind of vegetable.
The larvae of these are very much alike, being hard, leathery, wiry caterpillars, which vary in length to about three-quarters of an inch, according to age. These are mostly smooth, and have six feet on their thoracic segments, and a false foot or _proleg_ in the middle of the underpart of the terminal section of the abdomen-characters by which wire-worms may be distinguished from all others. Their length varies with age; as they live for some years in the larva state, so the different sizes mark so many broods, which in some fields are annually provided for. It should here be observed that the wire-worm does not breed; these larvae can only be hatched from the eggs of the female click-beetle: hence, then, destroying the worms prevents the development of their parent.
Now, as we have seen whole fields of wheat destroyed by wire-worms, it becomes important to examine the nature of this attack, with a view to point out a remedy. If, then, we go into a corn field in early spring, and see the young wheat blades looking yellow and sickly, we shall seldom be long in finding the wire-worm, on carefully taking up some of the affected plants. Its position will be at the base of the plant, sometimes eating its way into its centre, and so eating out its very heart; or perhaps it may nibble away the outer coat of the young stem, and so prevent any nutriment pa.s.sing into the blade. One worm will be enough to kill a single blade; but, alas! it frequently happens that he either visits all the blades, or is a.s.sisted by many individuals to each plant. This abundance we have observed more particularly on the breaking up of old pastures, old seeds, or saintfoin _lea_, in which not only have we many broods of wire-worms, but the eggs of a fresh lot, which hatch in time to eat the spring wheats. Again, this large increase we have ever observed in districts where rooks are few or much molested.
The rook is a constant visitor to the clover field; but when the plant is young he is driven off, because the farmer ”cannot think what else he can come for but the clover buds;” and when he sees some of these strewing the ground where the birds have been, he is confirmed in his opinion: but, if he carefully looked at the buds themselves, he would find them of a sickly hue, however recent the attack, and, if he looked deeper he might find the real enemy.
Fortified, then, with repeated observations of this kind, if asked how best to keep under wire-worms, we say most unhesitatingly, encourage the rook: he is one of the farmer's best labourers; and though, like John, and d.i.c.k, and Hodge, he will sometimes run into mischief, it is surely better to inst.i.tute a judicious police than to condemn and execute without very strong evidence.
Yarrell, in his beautiful ”British Birds,” has the following remarks upon this highly-important subject:-
The attempts occasionally made by man to interfere with the balance of powers as arranged and sustained by Nature, are seldom successful. An extensive experiment appears to have been made in some of the agricultural districts on the Continent, the result of which has been the opinion that farmers do wrong in destroying rooks, jays, sparrows, and, indeed, birds in general on their farms, particularly where there are orchards. In our own country, particularly on some very large farms in Devons.h.i.+re, the proprietors determined, a few summers ago, to try the result of offering a great reward for heads of rooks; but the issue proved destructive to the farms, for nearly the whole of the crops failed for three successive years, and they have since been forced to import rooks and other birds to stock their farms with. A similar experiment was made a few years ago in a northern county, particularly in reference to rooks, but with no better success; the farmers were obliged to reinstate the rooks to save their crops.
But as, perhaps, the most interesting account of the value of rooks will be found in an extract from the _Magazine of Natural History_, vol. vi.
p. 142, we cannot do better than transcribe it:-
”In the neighbourhood of my native place (in the county of York),”
says the writer, Mr. T. c.l.i.thero, ”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 larvae; 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 be correct, there is the enormous quant.i.ty of 468,000 lb., or 209 tons, of worms, insects, and their larvae, destroyed by the rooks of a single rookery in one year. To everyone who knows how very destructive to vegetation are the larvae 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-cla.s.s 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 pygmaeus_) 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.”
[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 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.