This is a fun genus in the subfamily Saltusaphidinae — a group that feeds mostly on sedges and rushes. F.W. Quednau recently finished a major revision of the group, and I had the pleasure of sharing specimens and correspondence with him throughout much of the project. Quednau was publishing on aphids before I was born.
Allaphis cyperi (Walker)
This is a very widely distributed species that feeds on Carex leaves (sedges), especially in wet places near streams, seeps, etc. Like many aphids that feed on grasses and sedges, this species is long and narrow in shape. Of the Saltusaphidinae I find in my field work, this is the most common. I have material from Oregon, Utah, Washington, and New Mexico.