Imágenes de páginas
PDF
EPUB

covers, and Riley mentions another beetle of the same genus, (calosoma calidum), having copper-colored spots on the wing-covers, figured upon a succeeding page, as having been seen by him preying upon this insect. Many of the larvæ are also devoured by birds.

CUT-WORMS.-In his first annual report of the Noxious and Beneficial Insects of Missouri, Riley described twelve species of cutworms. Hence the cut-worm " is only one of the twelve species, the peculiar habits of which can only be given by knowing the particular species referred to. Each of these twelve species is a caterpillar, the larva of a moth, which feeds during the night, remaining just beneath the surface of the ground during the day. They are called cut-worms from their habit of cutting off the stem or other portion of the plant on which they feed. Riley says of these caterpillars, "all of them are smooth, naked, and greasylooking worms of some shade of green, gray, brown or black, with a polished, scaly head, and a shield of the same color upon the top of the first and last segments; while most of them have several minute shiny spots on the other segments, each spot giving rise to a minute, stiff hair. They have the habit of curling up in a ball when disturbed. They produce moths of sombre colors, which are known as Owlet or Rustic noths. These moths fly for the most part by night, though some few of them may be seen flying, especially in cloudy weather. They frequently, even in large cities, rush into a room, attracted by the the light of gas or candle, into which they heedlessly plunge, and singe themselves. They rest with the wings closed more or less flatly upon the body, the upper ones entirely covering the lower ones, and these upper wings always have two, more or less distinctly marked spots, the one round, the other kidney-shaped.”'

"The natural history of most of these cut-worms may be thus briefly given. The parent moth attaches her eggs to some substance near the ground, or deposits them on plants, mostly during the latter part of summer, though occasionally in the spring of the year. Those which are deposited during late summer, hatch early in the fall, and the young worms, crawling into the ground, feed upon the tender roots and shoots of herbaceous plants. At this time of the year, the worms being small and their food plent

And

iful, the damage they do is seldom noticed. On the approach of winter they are usually about two-thirds grown, when they descend deeper into the ground, and curling themselves up, remain in a torpid state until the following spring. When spring returns. they are quite ravenous, and their cutting propensities having fully developed, ascend to the surface and attack the first green succulent vegetation that comes in their way. When once full-grown they descend deeper into the earth, and form for themselves oval chambers, in which they change to chrysalids. In this state they remain from two to four weeks, and finally come forth as moths, during the months of June, July, and August."

The accompanying cut (Fig. 4), represents the moth of one of our most common cut-worms, the Agrotis sub-gothica, of Haworth. Riley calls it, “The Western Striped Cut-worm.” The markings may be plainly seen upon the moth with expanded wings, while the other figure shows the moth while at rest. The dark spots are Fig. 4.

brown, the lighter portions, grayish flesh color. The moth of this species does not appear until August or September. The worm when full-grown is about one and one-fourth inches in length.

"Color, dirty white or ashgray, with three broad dark lines, and two light narrow ones along the sides, and a light one, edged on each side with a dark one, along the middle of the back.”—(Riley.)

There are several natural enemies to the cut-worms, among which are the ichneumon-flies, the parent flies of which deposit their eggs within the body of the worms, where they hatch and eventually canse their death. Riley says the spined soldier-bug, a cut of which is given on a succeeding page, also destroys then, as does the larva of the fiery ground-beetle. The ground-beetles, as a class, prey largely upon these worms. Poultry, as is well known, are of great assistance about a garden in destroying these, as well as other injurious insects.

THE ROUND-HEADED APPLE-TREE BORER. (Saperda bivittata, Say). This insect is unfortunately so well known to most orchardists as to scarcely need a description. The accompanying cut (Fig.

[graphic]
[ocr errors]

5) represents, Fig. 1, the perfect beetle, Fig. 5, the pupa, and also Fig. 5.

the larva at different stages of
growth, and the tree trunk, as
injured by the larva. The fol-
lowing description is from Ri-
ley's first Missouri Report.-
" The average length of the
larvæ when full-grown is about
one inch, and the width of the

first segment is not quite Fig. 6

inch. Its color is light yellow with a tawny yellow spot of

more horney consistency on Fig. 3

the first segment, which under
a lens is found to be formed of
a mass of light brown spots.

The head is chestnut-brown,
Fig. 4
Fig1

polished and horny, and the
the jaws are deep black. The

pupa is of rather lighter color Fig . 5

than the larva, and has transFig. 2

verse rows of minute teeth on the back, and a few at the extremity of the body; and the perfect beetle has two longitudinal white stripes between three of a light cinnamon color. The two-striped saperda makes its appearance in the beetle state during the months of May and June, and is seldoin seen by any but the entomologist who makes a point of hunting for it, from the fact that it remains quietly hidden by day, and flies and moves only by night. The female deposits her eggs during the month of June, mostly at the foot of the tree, and the young worms hatch and commence boring into the bark within a fortnight afterwards. These young worms differ in no essential from the fullgrown specimens, except in their minute size; and they invariably live, for the first year of their lives, on the sap-wood and inner bark, excavating shallow, flat cavities which are found full of their sawdust-like castings. The hole by which the newly-hatched worm penetrated is so very minute that it frequently fills up, though not till a few grains of castings have fallen from it, but the presence of the worms may be detected, especially in young trees, from the

[graphic]
[ocr errors]

*

bark, under which they lie, becoming darkened, and sufficiently dry and dead, to form cracks. Through these cracks, some of the casting of the worm generally protrude, and fall to the ground in a little heap, and this occurs more especially in the spring of the year, when with the rising sap and frequent rains, such castings become swollen, and augment in bulk. It is currently supposed that this borer penetrates into the hardwood of the tree, after the first year of its existence, whereas the flat-headed species is supposed to remain for the most part immediately under the bark; but I find that on these points no rule can be given, for the flat-headed species also frequently penetrates into the solid heart-wood, while the species under consideration, is frequently found in a full-grown state under the inner bark, or in the sap-wood. The usual course of its life, however, runs as follows: As winter approaches, the young worm descends as near the ground as its burrow will allow, and doubtless remains inactive until the following spring. On approach of the second winter, it is about one-half grown, and still living on the sap-wood, and it is at this time that these borers do most damage, for when there are four or five in a single tree, they almost completely riddle it. In the course of the next summer, when it has become about three-fourths grown, it generally commences to cut a cylindrical passage upwards into the solid wood, and before having finished its larval growth, invariably extends this passage right to the bark, sometimes cutting right through a tree to the opposite side from which it commenced, sometimes turning back at different angles. It then stuffs the upper end of the passage with sawdust, like powder, and the lower with curly fibres of wood, after which it rests from its labors. It thus finishes its gnawing work during the commencement of the third winter, but remains motionless in the larval state until the following spring, when it casts off its skin once more, and becomes a pupa. After resting three weeks in the pupa state, it becomes a beetle with all its members and parts soft and weak. These gradually harden and in a fortnight more it cuts its way through its sawdust-like castings, and issues from the tree through a perfectly smooth and round hole. Thus it is in the tree a few days less than three years.

REMEDIES.-From this brief sketch of our Round-headed Borer, it becomes apparent that plugging the hole to keep him in, is on a

ers.

par with locking the stable door to keep the horse in after he is stolen; even supposing there was any philosophy in the plugging system, which there is not. The round, smooth holes are an infallible indication that the borer has left; while the plugging up of any other holes or cracks, where castings are seen, will not affect the intruder. This insect probably has some natural enemies belonging to its own great class, and some of our wood-peckers doubtless seek it out from its retreat and devour it; but its enemies are certainly not sufficiently under control, and to grow healthy apple-trees we have to fight it artificially. Here again prevention will be found better than cure, and a stitch in time will not only save nine, but fully ninety-nine.

Experiments have amply proved that alkaline washes are repulsive to this insect, and the female beetle will not lay her eggs upon trees protected by such washes. Keep the base of every tree in the orchard free from weeds and trash, and apply soap to them during the month of May, and they will not likely be troubled with bor

For this purpose soft-soap or common bar-soap can be used. The last is perhaps the most convenient, and the newer and softer it is the better. This borer confines himself almost entirely to the butt of the tree, though very rarely it is found in the crotch. It is therefore only necessary, in soaping, to rub over the lower part of the trunk and the crotch, but it is a very good plan to lay a chunk of the soap in the principal crotch, so that it may be washed down by the rains. In case these precautions have been unheeded, and the borer is already at work, many of them may be killed by cutting through the bark at the upper end of their burrows, and gradually pouring hot water into the cuts so that it will soak through the castings, and penetrate to the insect. But even where the soap preventive is used in the month of May, it is advisable to examine the trees in the fall, at which time the young worms that hatched through the summer may be generally detected and easily cut out without injury to the tree. Particular attention should also be paid to any tree that has been injured or sun-scalded, as such trees are most liable to be attacked."

D. B. Wier, of Lacon, Illinois, treats his orchard as follows: “I will suppose that I have a young orchard, of any number of trees, say a thousand. The second season after planting, about the last of July, or during the first half of August, with a common hoe, I

« AnteriorContinuar »