The natural ratio of increase of this insect being very great, nature has provided means to curtail it. Being a somewhat conspicuous object, the larvæ sometimes serve as a dainty meal for some of the larger insectivorous birds, but is much oftener attacked and destroyed by parasites of several distinct species, all of which, in the larvæ state, live within the body of the caterpillar, and rioting on its substance finally occasion its death. One of these is shown in Fig. 4, a fat, legless grub or maggot, which is the progeny of a handsome four-winged fly, of a yellowish brown color, known as the long-tailed ophion fly, (Ophion Macrurum,) Fig. 5. The female fly deposits her eggs on the skin of her victim, fastening them firmly there; these, when hatched, eat their way through the exterior, and at once begin to feed upon the fatty parts within.
A two winged fly, known as a Tachina fly, very similar if not identical with the species known as the red-tailed Tachina fly, Exorista Militaris, figure 6, is often found infesting the Cecropia Caterpillar. The larvæ of this fly are of a translucent yellow color, and when mature, eat their way out of their victim and change to the chrysalis state under the ground. There are also two smaller species of parasites, known as Chalcis flies, which are destructive to this insect; one of these, (Chalcis Maria,) is shown in Fig. 7, much enlarged, the cross lines at the side showing the natural size.
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MILDEW ON THE BLACK CURRANT.
BY REV. W. STEWART DARLING, TORONTO.
I should be glad if in the next number of the HORTICULTURIST the editor would say whether he has seen or heard of a sort of blight or mildew which here has fallen on the black currants, and which, if it spreads, will put an end to the culture of that fruit. I have some beautiful black Naples bushes from which I have never had any perfect fruit; although a man who knows something about it said the other day, I ought to have half a bushel of currants from each tree. Soon after the foliage is fully developed, I observe here and there that the leaves begin to assume an upright tendency around the edges; underneath I find an almost invisible film, which however is so slight that I can assure myself of its presence only by passing my fingers over the under side of the leaves, after which there is a perceptible “stickiness,” which contact with healthy leaves does not produce. This continues to increase till the film becomes white, and passes over on to the upper side of the leaf in the form of mildew. This subsequently becomes brown, and the leaf, or part of it, will crumble as if scorched with fire. The power of the leaf is evidently destroyed before this stage; the fruit is arrested in its growth, and even that which is tolerably matured is dry and almost useless. I can detect no trace of insect life, nor could a well-known entomologist, who looked at them last summer, suggest the cause. I treated them with whale-oil soap in strong solution, and though I fancied that it retarded the growth of the evil it had no ultimately good effect. I have cut them back rather closely and propose to try salt on one row and sulphur on another. The land is light and warm, but well enriched; but land equally poor, not far off, had good fruit on it, while mine yielded nothing.
Not only in my own interest, but in that of others, I should be glad if some of our skilled fruit growers could give their attention to this matter.
[NOTE.—Not having noticed this mildew, the editor requests any members who have been troubled with it to give their method of treatment.]
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