Holotype United States: California [?Mus. Regensberg]. Based upon information supplied by J.W. Weidemeyer and upon a figure shown to Grote & Robinson by S. Calverley. This figure is probably that eventually published by Weidemeyer, Calverley & Edwards (1903: plate 13, figure 5 (STI 20511). The holotype is the specimen illustrated in this figure. Euproserpinus phaeton was redescribed by Grote & Robinson (1868: 181-182) (STI 18155), from material received from Boisduval. The type was stated by Comstock (1938: 34) (STI 17324) to be in the NHMUK. There is a specimen labelled "type" in the NHMUK, but this is almost certainly one of the subsequent specimens upon which Grote & Robinson based their redescription and therefore not the holotype.