Either one or two generations occur each year, depending on locality.

At times, a third generation occurs, with larvae in late August.

Two generations may occur each year at least in part of its range.

Two generations per year may occur as far north as southern England.

In temperate zones only one generation per year will occur.

In some locations, three or more generations may occur each growing season.

In southern Europe, a partial second generation may occur.

One generation per year occurs in the north, and two or more in the south (Wagner 2005).

There are two generations per year, although a partial third generation may occur.

In the 1890s the founding generation of teachers left, and a second generation occurred.