butterfly stitch

(multiple of 10 sts plus 9)
Note On rows 10 and 20, work butterfly stitch loosely.
Rows 1, 3, 5, 7 and 9 (RS) K2, *wyif sl 5, k5; rep from *, end wyif sl 5, k2.
Rows 2, 4, 6 and 8 Purl.
Row 10 P4, *insert LH needle down through the 5 loose strands below next st, p these 5 strands tog with next st on needle, p9; rep from *, end last rep p4.
Rows 11, 13, 15, 17 and 19 K7, *wyif sl 5, k5; rep from *, end wyif sl 5, k7.
Rows 12, 14, 16 and 18 Purl.
Row 20 P9, *insert LH needle down through the 5 loose strands below next st, p these 5 strands tog with next st on needle, p9; rep from * to end.
Rep rows 1-20.