$9 
Description and life history.—The larve, or slugs, as they are im- 
properly called, are white at first, but soon become covered with an 
olive slime, which gives them something of the appearance of the 
naked snail to which the. name slug properly belongs. ‘They are 
further easily distinguished from any other larve feeding upon the 
leaf by the fact that they are much thicker in front than behind, 
tapering gradually posteriorly. They have twenty very short legs, 
the first three pairs jointed, the remainder fleshy prominences, com- 
monly known as projiegs. The head is of a dark chestnut color, 
small, and usually concealed under the fore part of the body. They 
live mostly on the upper side of the leaves of the trees, eating away 
all the parenchyma, leaving only the veins and epidermis of the 
under side. The slugs shed their skins five times, and after the last 
moult they lose their slimy covering and olive color, and are then 
yellow and free from mucus. From the 1st of July to the middle 
of August, having gained their growth, they leave the trecs and bur- 
row to the depth of one to four inches, forming an oval cavity in 
the earth, where the change to pupa occurs. From these cells they 
escape in the form of saw-flies from the middle of July to the last 
of August. The winged insect is about one-fifth of an inch in length, 
and is of a glossy black color, excepting the first two pairs of legs, 
which are a dirty yellow or clay color, with blackish thighs, and the 
hind legs, which are dull black with clay colored knees. The wings 
are transparent, iridescent, with brownish veins, and with a smoky 
cloud or band across the middle of the third pair. These saw-flies 
may be found on the leaves of the trees in early morning, or in the 
cool of the evening, at which time they are sluggish, and not easily 
disturbed. Their eggs are laid singly within little semi-circular in- 
cisious through the skin of the leaf. From these a second brood of 
the slugs soon hatch, which get their growth and go into the 
ground again in September and October, remaining there until the 
following spring, when most of them are changed to flies and leave 
their winter quarters. Some of them, however, commonly remain 
unchanged in the ground until the following year, so as to continue 
the species if any complete destruction should overtake the remainder 
of the brood. These spring flies lay their eggs as already described, 
usually in June, the minute worms appearing in about a fortmght 
afterwards. 
Remedies.—Various substances have been suggested for the destruc- 
tion of thistpest, but unfortunately some of those most generally 
recommended have really little effect. Among these remedies of 
doubtful efficiency I may mention fine sand, and dust and ashes. 
Some experiments made with these substances by Mr. Wim. Saunders, 
of Ontario, Canada, are worth quoting entire: 
‘“As soon as the slugs were observed at work in the spring, they 
were treated to a plentiful supply of dry sand, thrown up into the 
higher branches with a shovel, and shaken over the lower ones with 
a sieve, which stuck thickly to their slimy skins, completely cover- 
ing them up. Thinking we must have mastered them by so free a 
use of this long trusted remedy, we took no further heed of them for 
some days, when, to our surprise, they were found as numerous as 
ever. The next step was to test this sand remedy accurately to see 
what virtue there was in it. Several small branches of pear trees 
