This is variation of fly stitch which goes under the name of Closed Fly stitch. It is simple work for is consists of a number of fly stitches stacked together.
As you work each individual fly stitch you pack the y shapes close together and sew a small tying-down stitch.
This variation of fly stitch also creates a ridge line down the center of the stitch.
This stitch can also be used as a filling for long, narrow shapes by graduating the widths of the stitches, or it can be worked solidly, row on row, for filling a larger shape.
This stitch is often employed to work leaf like shapes and foliage in floral sprays.
It is ideal to tuck in and around flowers in Silk Ribbon Embroidery or in Brazilian Embroidery.
There are a number of varieties and developments of Fly stitch. These are listed under Closed fly stitch, Plaited fly stitch, Reversed fly stitch, Threaded fly stitch, Threaded reversed fly stitch, Whipped fly stitch, and Whipped reversed fly stitch.