A few insects will now be noticed more in detail.
Selandria cerasi, or Blennocampa cerasi, is the common Slug of the cherry and pear trees, and quite a troublesome hymenopterous insect. In some parts of the United States these little creatures are so numerous as to strip the substance from the foliage of pears and cherries.
Our Slug resembles the Selandria œthiops of Europe, but is declared to be different. The larvæ are at first white, but the slimy substance that oozes from their bodies covers them with an olive coating. They have twenty very short legs; when fully grown, the largest are about nineteen-twentieths of an inch long. The head is concealed under the fore part of the body, which is largest before, and tapers behind. They attain their growth in twenty days, casting their skins five times, eating them until the last time, after which they remain free from viscidity, and are of a clear yellow color. They leave the tree and enter the ground to the depth of one or three inches, to form their chrysalids. In three days they come up as flies, in July and August, to lay eggs for a second brood, the pupæ of which remain in the ground during the winter.
Another insect of this genus is very destructive to our rose bushes; it is called Selandria rosæ.
Selandria vitis, is a species that appears upon our grape vines, and is quite troublesome in some vineyards in July. They feed in companies of a dozen or more.
Remedies.—Shaking them off the leaves has been recommended, but does not promise to be effectual. When few, they should be sought for and crushed, to prevent their increase. Though troublesome, this may be effectually done, and their ravages leave traces that will direct us to the leaves which contain them.
When more numerous, the foliage may be syringed with common soapsuds, or with the whale oil soap, two pounds to fifteen gallons of water.
Air-slaked lime has been dusted upon them with good effect; ashes, and even dry dust from the road, will destroy them, by adhering to the slimy surface. These applications are best made when the foliage is wet after a shower, or with the dew. The great difficulty consists in their habit of going under the leaves, and thus being protected.
Mr. Parkman, the noted rose fancier, has found a mixture of soap and petroleum of great service, as it kills the slugs without injuring the buds and foliage. To a gallon of soft soap he adds two-thirds of a pint of petroleum, mixes them thoroughly, and dissolves in half a barrel of water; to be applied with a syringe.
Diptera.—Dr. Fitch describes as a new species Malobrus mali. He found them in a fruit that had been perforated by the Codling-moth. The larvæ are transparent; the flies resemble the Hessian-fly, that destroys the wheat plant.[44]