Colonies on agar Chapek rather fast-growing, on the 14th day up to 4 cm in diameter, radially wrinkled, granular, with white mycelium, abundantly spore-bearing in olive-green tones. Exudate is absent. The reverse is light yellow to bodily. On CYA, colonies reach a diameter of 4.5-5 cm in 14 days, velvety to woolly, radially folded, with olive-green sporulation, sometimes with a mild wine-red exudate. The cream-to-wine-red reverse; a wine-red, soluble pigment is released on Wednesday. On malt extract agar (MEA), colonies were about 5 cm in diameter on day 14, velvety or slightly grainy, abundantly spread in wormwood-green tones. Exudate is absent. Cream-red to wine-red, a rich wine-red pigment is released on Wednesday.
Conidiophores are strictly single-tier, short, 20-40 microns long, smooth-walled, swollen at the apex. Violets in a bundle of 10-15, 6-8 (12) microns in length. Conidia are ellipsoidal, smooth-walled or almost smooth-walled, 2–2.5 × 1.5–2 μm, collecting in loose columns.
The name refers to the red pigment secreted by the fungus when cultivated on agar with malt extract: cochineal and kermes are red dyes made from dried insects.
Penicillium chermesinum Biourge , La Cellule 33: 284 (1923).
The strain IMI 191730 = CBS 231.81 = NRRL 2048 = FRR 2048 = IFO 31745 was selected as a neotype corresponding to the description of Philibert Bjurge. This strain belongs to the Charlesia section; modern descriptions of the species are based on this strain and its close ones. Strain NRRL 735, obtained from Bürges by Charles Tom under the name Penicillium chermesinum , does not correspond to the description of the author of the species, is currently assigned to Penicillium cvjetkovicii from the section Cinnamopurpurea [1] .