Hydraecia obliqua (Harvey)

Crabo, Lars G., Davis, Melanie, Hammond, Paul, Tomas Mustelin, & Jon Shepard,, 2013, Five new species and three new subspecies of Erebidae and Noctuidae (Insecta, Lepidoptera) from Northwestern North America, with notes on Chytolita Grote (Erebidae) and Hydraecia Guenee (Noctuidae), ZooKeys 264, pp. 85-123 : 105-106

Hydraecia obliqua (Harvey) Figs 21-23

Gortyna obliqua Harvey 1876: 53. Type locality: [USA], California, [Mendocino]. NOTE: Gortyna obliqua was described from a single specimen. Poole (1989) states that the holotype is in the BMNH. This appears to be incorrect because all Harvey type material, including that in the BMNH, was examined by Barnes and Benjamin (1924) who concluded that a specimen in the AMNH labeled "Mendocino, California/4410/No. 10703 Collection Hy. Edwards/ Apamea obliqua . Harv." is the type.

Gortyna ximena Barnes and Benjamin 1924: 160. Type locality: [USA], California, Truckee. syn. n.

Gortyna columbia Barnes and Benjamin 1924: 161. Type locality: [Canada], B[ritish] C[olumbia], Saanich District. syn. n.

Remarks.

More than a decade ago, prior to the availability of mitochondrial DNA, the senior author conducted a study of the genus Hydraecia Guenée focusing on the western North American species related to Hydraecia obliqua (Harvey), herein referred to as the Hydraecia obliqua species-group for convenience. These moths occur over a large area spanning the Pacific Coast to the Great Plains west to east and British Columbia, Alberta, and Saskatchewan to southern California, northeastern Arizona, and northern New Mexico north to south. This study included examination of all primary types, assembling over 600 specimens from most large institutional and many private North American collections, and examination of over 60 genitalia preparations. The conclusion was that Hydraecia intermedia (Barnes & Benjamin), known only from the holotype from Fort Calgary, is distinct but that all other populations in the species-group exhibit nearly continuous clinal variation in maculation and genitalia to form a circle of races (rasenkranz) from California, across Montana, and ending in the montane forests of the Southwest. This work was accepted for publication but was withdrawn because of the author’s concern that somewhat distinctive populations on the Pacific Coast and in the Southwest might be different species from the widespread intervening population but that the genitalia structure lacked differences sufficient for resolving the species.

Since then, barcodes have demonstrated a consistent 2% difference between populations from near the Pacific Coast (northern California, Washington, and British Columbia (n=6)) and those from farther inland (Colorado, Washington, Wyoming, Alberta, and British Columbia (n=7)) that along with slight differences in maculation suggest that they are best treated as distinct species. The western species is Hydraecia obliqua and the eastern one is Hydraecia medialis Smith.

Hydraecia obliqua occurs east to the Sierra Nevada in California and the crest of the Cascade Range in Oregon and Washington. It occurs continuously on the coast north to southwestern British Columbia, with a disjunct northern population at Terrace, British Columbia. Its forewing is warm orange brown, varying considerably in darkness from dark brown on the California Coast (Fig. 21), lighter orange brown in the Pacific Northwest (Figs 22-23), and pale yellow brown in the Sierra Nevada. The hindwing is pale with a yellow tint, usually with dark veins and a gray suffusion in the submarginal area. The forewing pattern is similar to that of Hydraecia medialis , especially where they approach each other in the PNW, with slight differences that are described under Hydraecia medialis .

An area of possible intergradation between Hydraecia obliqua and Hydraecia medialis in Oregon is discussed under Hydraecia medialis .