364 MONTHLY JOURNAL OF AGRICULTURE. 



the year 1846 in Prince George's County was destroyed by the Horn or Tobacco 

 Wor?n. They are produced by the horn or unicorn fly, as they are very appro- 

 priately called. This fly lays its eggs after sunset, chiefly on the under side of 

 the leaf of the larger plants of tobacco, nearer the top than the bottom of the 

 plant. They proceed very rapidly, darting from plant to plant, and usually lay 

 but one egg on a leaf. They hatch in from four to eight days, and begin to eat 

 as soon as hatched. At this period they may be easily found and destroyed, by 

 a very small hole eaten through the plant. In a few days they rove about the 

 leaf. When about one-fourth grown they crawl from one leaf to another, and 

 when about two-thirds grown they descend the stalk, and in the heat of the 

 day sometimes retire into the cool earth, under the lower leaves of the larger 

 plants. They as frequently ascend another plant as the one from which they 

 have descended. They, like the silk-worm, shed two or three times before they 

 get their growth, and at each time cease to eat for several hours. They require 

 from two to three weeks to arrive at maturity, soon after which they descend 

 the plant and bury themselves in the field at various depths, from 4 inches to two 

 feet deep. I am not aware that the tobacco worm surrounds himself with any 

 kind of covering, as the silk-worm does. He remains in the earth, in the chrysa- 

 lis state (having changed his color to a bright yellow) from autumn, exhibiting 

 the impression of the wings and proboscis only, until the more genial season of 

 the ensuing year enables him to fully change his character, when he appears 

 above the ground, a busy, active insect, sipping honey from blossom to blossom. 

 I have no idea how long they live after they have obeyed the great law of Na- 

 ture in propagating their race. There are usually two gluts* of worms ; the 

 first glut appears about the last of June or first of July. The worms that mature 

 and escape into the earth from this glut are supposed to produce a portion of the 

 second glut. The second glut appears the last of August or first of September. 

 This glut is much the most numerous and destructive, coming as they do when 

 the tobacco is generally large and a portion of it ripe, and requiring all the force 

 on the plantation to house it. The worms feed principally upon the ripe leaves, 

 though they do eat the green top leaves, and even the suckers, which put out after 

 the tobacco has been topped. Turkeys are very generally used as auxiliaries to de- 

 stroy the worms ; they, when not raised, are bought expressly for that purpose. 

 When the tobacco is not too large, the worms from a fourth to half grown, and the 

 turkeys large, they destroy them in immense numbers. When the tobacco is large 

 and the worms nearly grown, the turkeys are not worth the trouble of keeping 

 them in the tobacco-field. The great increase of the horn worm is ascribed in part 

 to the fact that very few planters now fire their tobacco. Millions of the worms 

 are carried to the house on the tobacco, and escape into the earth in and near the 

 tobacco-house, and add incalculably to the number that had been left in the field. 

 It is supposed that mild winters are favorable to the production of the tobacco 

 fly, as well as to all the insect tribe. Upon this subject I confess I am some- 

 what skeptical. It is certain that a scarcity of the various insects is not uni- 

 formly the result of very hard winters. Of the fly that attacks the young plant 

 in the bed there are, I believe, two kinds, or at least two sizes, and they of dif- 

 ferent forms and color. The larger kind I believe to be identical with the turnip 

 %. The smaller kind is extremely small, so small as not to be easily seen, ex- 

 cept when in motion. Cold, dry, windy weather is most favorable to the rav- 

 ages of the tobacco fly. 



Many remedies have been tried, but none, I believe, with entire success. 

 Pine brush spread over the bed immediately after it is sown, is a practice, in 

 this and the adjoining counties, very generally adopted as a protection against 

 the ravages of the fly. Whether the plant covered up and excluded from the 

 sun is not palatable to the fly, is of course an unsettled question. The brush 

 is taken off the bed as soon as the plants are large enough to be considered 

 out of danger from the fly, and ought to be done in mild, moist weather. — 

 Slaked ashes sown lightly' over the bed when the dew is on, and freshly slaked 

 lime sown in the same manner, have been recommended by some persons as 

 remedies. Stable manure is used for the same purpose, which has at least this 

 advantage. It is certainly a good top-dressing for the young plants, and protects 



* The word glut, as here used, means the appearance of an immense number of worms at the same 

 time. 



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