Amphipoea interoceanica (Smith, 1899)
Strawberry Cutworm Moth
Backus Woods, St Williams
July 30, 2009, J. Troubridge.
Specimen courtesy of CNC
Photograph copyright: Merrill A. Peterson
Amphipoea interoceanica is a small (FW length 12-13 mm) burnt orange moth with a net-like pattern of veins and lines and white or bright orange-filled reniform spot that has been recorded from Vancouver Island but might not be a permanent resident of the Pacific Northwest. The forewing is stout with a weakly falcate apex, It is nearly uniform dull burnt orange with darker veins, slightly darker and grayer in the anterior subterminal area and in all of the terminal area except at the apex. The transverse lines are similar to the veins in color. The basal, antemedial, and postmedial lines are double with wide separation of the inner and outer components and filling of the ground color. The orbicular spot is also similar in color to the lines and veins. The reniform spot is large, with the lateral two-thirds filled with white or warm orange color.
This species is closely similar to Amphipoea americana, a more common and widespread moth in the Pacific Northwest. Amphipoea interoceanica is smaller and tends to have white rather than orange filling of the reniform spot, the opposite preponderance of A. americana. In individuals with white spots the filling does not include the medial edge of the spot in A. interoceanica but fills most of it in A. americana. The orange-spotted form of A. interoceanica also resembles Amphipoea pacifica; however, A. pacifica has an orange instead of a gray hindwing. These species are unlikely to occur together since the range of A. pacifica is limited to Oregon in our region.
Genitalia differences between A. interoceanica and A. americana can be examined without dissection by removing the scales from the tip of the abdomen with a fine brush. The tip of the valve of A. interoceanica lacks a long digitus, a structure that protrudes ventral to the distal valve in A. americana. In females, the 7th sternite of A. interoceanica have a deep notch that A. americana lacks (species page on the E. H. Strickland Museum website (University of Alberta)).
The habitat of this moth in the Pacific Northwest is unknown.
This species has been confirmed as occurring only at Duncan on southern Vancouver Island (Canadian Nation Collection). It might be more widespread in the Pacific Northwest since distinguishing it from A. americana with certainty requires examination of the genitalia. The single occurrence of this moth in the Pacific Northwest could potentially be through accidental introduction from eastern North America such as from transfer of infested strawberry plants.
This moth occurs from Arizona and Alberta to the Atlantic outside of the Pacific Northwest. The latitudinal range in the East is from Nova Scotia to North Carolina
The larvae bore in strawberries (Fragaria spp. (Rosaceae)) as well as grasses and sedges.
Adults are nocturnal and come to light. The flight period outside of the Pacific Northwest is late summer.
This species is an occasional pest of cultivated strawberries.