Planting the onions in a new place as remote as possible from where
they were grown the previous year has been found useful, as the flies
are not supposed to migrate very far.
Pulverized gas lime scattered along between the rows has been useful
in keeping the flies away.
Watering with liquid from pig pens collected in a tank provided for
the purpose, was found by Miss Ormerod to be a better preventive than
the gas lime.
When the onions have been attacked and show it by wilting and changing
color, they should either be taken up with a trowel and burned, or
else a little diluted carbolic acid, or kerosene oil, should be
dropped on the infested plants to run down them and destroy the
maggots in the roots and in the soil around them.
Instead of sowing onion seed in rows, they should be grown in hills,
so that the maggots, which are footless, cannot make their way from
one hill to another.
THE CABBAGE BUTTERFLY.
_Pieris rapae_ (Linn.)
In the New England States there are three broods of this insect in a
year, according to Mr. Scudder, the butterflies being on the wing in
May, July, and September; but as the time of the emergence varies, we
see them on the wing continuously through the season.
[Illustration: FIG. 12.]
The expanded wings, Fig. 12, male, measure about two inches, are white
above, with the base dusky.
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