Imágenes de páginas
PDF
EPUB

is this work regarded by the successful tobacco planter, that he will neglect every other duty on the farm and pay three or four times the ordinary prices for farm hands in order to fight this pest, for the profits of tobacco culture will be, other things being equal, proportioned to the ability to destroy this inveterate and insatiable enemy.

The fruitful mother of the devouring and destructive tobacco worm is a lepidopterous insect of the hawk moth or Sphingida family, also called the Sphinx moth. It derives the name Sphinx from the attitude which the caterpillar assumes in raising the fore part of the body, and remaining in this state of immobility for hoars together. In this the lively imagination of Linnaeus perceived a resemblance to the sphinx of the Egyptians. There are two species of these moths—the tobacco worm of the North—Phlegethontius celeus, shown in Fig. 68, and the tobacco worm of the South—Phlegethontius Carolina, Fig. 69. Both species may occur in the Middle South, and for the purpose of the practical planter may be considered as one, though entomologists have had a dispute over their proper names, the one above adopted having by far the weight of evidence and authority in its favor.

The worm enters immediately upon its work of destruction, making a small hole in the leaf, and gradually enlarging this, confining itself to the under surface of the leaf if the weather is clear. About the seventh day it passes through another change, doffing its old skin and putting on the habiliments of maturity. While this change is going on, the caterpillar loses its appetite, but in a lay or two it recovers and becomes endowed with greater vigor, activity and voraciousness, passing readily from leaf to leaf, or from plant to plant, growing in size and its capacity for eating, until it will consume half a large leaf within twenty-four hours. As it approaches its full growth, it takes refuge, during the heat of noontide, among the ruffles of the plants, or screens itself from the ardent rays of the sun by Irene-

[graphic][merged small]

trateng thp soft earth under the plant. At this stage of its growth (Fig. 68, better shown in the engraving from a photograph, Fig. 70) it is a hideous looking creature, between two and three inches long, and as large as the little finger. It has a dark, green color, with a sharp, pointed spikelet upon its tail resembling the sting of a bee. This is often called a "horn," hence the name horn worm. Oblique, whitish, dotted stripes point downward and backward, and ornament its sides. It has twelve segments or rings; six true legs, coming out from the second, third and fourth rings, and four double, fleshy suction protuberances from the seventh, eighth, ninth and tenth segments, with a prop leg on the twelfth. The fifth, sixth and eleventh segments have no legs. When touched, the worm manifests its irritability by throwing its head from side to side, ejecting from its mouth a stream of masticated tobacco, and chafing its mandibles, emitting a sound like the chattering of teeth. Though threatening in appearance, it is perfectly harmless, and can be handled with impunity.

This moth rarely makes its appearance in the day until about sunset, when it may be seen with its long tongue probing the deep corollas of the petunia, evening primrose, and of the jiinson or Jamestown, weed, at which time it is easily caught. This moth (Fig. 68) measures across the wings from four to five inches, has a gray color, variegated with wavy black lines across the wings, and fine orange colored spots on each side of the abdomen. The tongue is five or six inches long, and when not in use is coiled up spirally, like a watch spring. Its first appearance is about the middle of May. From this time, the number increases until the last of August. From their large size, the manner of their flight and method of feeding, they are often mistaken for humming birds and are called "Humming bird moths" and "Horn flowers."

The eggs, about the size of a mustard seed, and of a pea-green color, are deposited both upon the upper and under surface of the tobacco leaf, being kept in place by a viscid fluid resembling glue. The moth, in depositing the eggs, flies rapidly from plant to plant, giving each leaf upon which it deposits an egg, an audible tap. This is done usually at twilight, and after, in clear weather. The eggs gradually change their color to a milky white, and even before the tiny worm breaks from the shell, its spiral form is distinctly visible through the transparent encasement. When first hatched, it is of a delicate cream color, with a white, thornlike appendage. When it has attained its full growth, which occupies the period of about twenty days, it descends into the ground, when its body contracts and shortens, the skin meanwhile changing from a dark green to a brown color and increasing in hardness; within a week or two it will assume the chrysalis state, with a long tongue case bent over circularly from the head and touching the breast, making a complete loop (Fig. 68), hence they are sometimes called "Jug handle grubs."

Entomologists usually concur in the belief that in this condition it remains in the ground, below the freezes, through the winter. Many practical, observant farmers, however, are of the opinion that this is true only as applied to those that appear later in the season, just before, or after, the appearance of frost. It is believed that those coming to maturity in June and July throw off the chrysalis state in August and September, and appear as moths. In this way only can the large number of worms that appear in these months be accounted for.

There is another moth, the Sphinx quinque-maculata, that resembles the latter so much that an ordinary observer will scarcely distinguish the difference. This is another species of the same family, and the larvae of the moth prefer the tomato vine, especially in the Southern States, but they are very destructive to the tobacco plant in higher latitudes.

[graphic]

Fig. 72. Development Of YOUNG Broom Bape. Three-fourths natural size.

ii, A plant which is just beginning: to put out the stalk bud and the fibrous roots; 6, a later stage when the closely placed fibrous roots form conspicuous prom* inences which conceal most of the surface; c, two parasites at a still later stage, the right one turned so as to show the bud, now of considerable size; d, a still later stage, with a short stem and bracts; e, a well-grown young parasite as it pushes through the ground at the surface. its long, fibrous roots not yet attached to those of the host plant; /, a young plant which was grown ii i packed soil, with several lateral buds which would have produced branches.

« AnteriorContinuar »