Mimulus aurantiacus was swapped into Diplacus aurantiacus without the infraspecific taxa being handled first. This created a false name, "Diplacus aurantiacus var. pubescens."

From Tulig & Nesom 2012, "Taxonomic overview of Diplacus sect. Diplacus (Phrymaceae)":

Although first described as a separate species, Diplacus calycinus has more recently been treated at subspecific or varietal rank within D. longiflorus (Grant 1924; Pennell 1951; Munz 1973). Thompson (2005) went even further in including D. calycinus simply as a synonym within his concept of Mimulus aurantiacus var. pubescens (= D. longiflorus), but results from the Tulig PCA and DFA indicate that D. calycinus is distinct from D. longiflorus, especially in corolla length, corolla tube length, and style length. Corolla color is cream to pale yellow in D. calycinus and salmon in D. longiflorus.

Diplacus calycinus and D. longiflorus are essentially allopatric to parapatric. Particularly in Fresno, Tulare, and Kern cos., where D. calycinus occurs completely separated from D. longiflorus (see Thompson's Fig. 63), it appears to be clearly distinct especially in abaxial leaf vestiture –– the hairs are unbranched, broad, and vitreous, compared to the branched, thinner, and dull hairs of D. longiflorus. The type of D. calycinus is a Sierran plant from Tulare County.

Overlap between the two taxa occurs only in southern California, especially in the region (in San Bernadino Co.) connecting the San Gabriel and San Bernardino mountains. In that area, flower color of individuals of D. calycinus ranges from light to dark orange, and corolla length is shorter.

and

9. Corollas cream to light yellow, tube-throat 48–55 mm; styles 38–46 mm....Diplacus calycinus
9. Corollas salmon, tube-throat 40–48 mm; styles 28–37 mm ..................Diplacus longiflorus