Semi-desert. Openings, woodlands, shrublands. Spring and summer.
Canyons of the Ancients National Monument, May 25, 2010.

Erigeron aphanactis has no rays on any of its flower and thus is unusual for an Erigeron. In the Four Corners region there are just two such Erigerons (E. compositus is the other) and there are perhaps another dozen in North America.

If you try to key these ray-less Erigerons, you may wind up with no answer to your search, because not all keys include such Erigerons. Fortunately A Utah Flora, Flora Neomexicana III, and Flora of the Four Corners Region do, but unfortunately Colorado Flora and Flora of Colorado do not. In the former there are notes about ray-less taxa but no actual entries in the key, and in the latter the key has conflicting entries:

1a. Ray flowers very numerous....... 2
1b. Ray flowers few to numerous.... 3
Although 1a. & 1b. do not mention ray-less Erigerons, somehow 3a. states ""Ray flowers absent...." and you can then proceed to 4a. Erigeron aphanactis  --  but there is never an indication that E. compositus can be ray-less. Flora of the Four Corners Region indicates that Erigeron compositus can "often" not have rays, and Weber agrees, indicating in a descriptive note that this form of E. compositus is "common", but unfortunately his key does not include rayless Erigerons!

Flora of the Four Corners Region gives us a clear picture of the Erigeron species lacking rays. The treatment was nicely done by Asteraceae expert Guy Nesom.
1. Heads disciform (ray/pistillate florets present, but corollas tubular or laminae [rays] absent or shorter than the involucres).....2
1' Heads radiate  ...................3

Entry 2 includes both Erigeron aphanactis and Erigeron compositus.

Notice that Nesom teaches us something about our terminology: These Erigerons are not really "ray flower-less". They are "ray-less". They do have ray flowers (often referred to as "ray florets" in technical floras), but the florets either lack a "lamina" (a ray) or the lamina is so minute that it does not even show above the tip of the phyllaries (the tip of the involucre).

Also note that the ray florets are infertile; they contain just pistils.

Erigeron aphanactis var. aphanactis (Rayless Fleabane, Rayless Daisy)
Asteraceae (Sunflower Family)  

Semi-desert. Openings, woodlands, shrublands. Spring and summer.
Canyons of the Ancients National Monument, May 25, 2010.

This species was first named Erigeron concinnus variety aphanactis by Asa Gray in 1865 from a specimen collected in Nevada by C. L. Anderson.  Edward Greene renamed the species Erigeron aphanactis in 1897.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Erigeron aphanactis