Identification
Field Guide Descriptions: Online Resources: MPG , BugGuide , iNaturalist , Google , BAMONA , GBIF , BOLD Technical Description, Adults: Forbes (1948); Schweitzer et al. (2011)Technical Description, Immature Stages: Forbes (1948); Wagner (2005); Schweitzer et al. (2011)
Adult Markings: A moderately large Prominent. The ground color of the forewings is ashy gray with a bluish cast when fresh (Forbes, 1948). The basal, antemedian, and postmedian lines are black, double, and filled with a slight yellowish shade. More conspicuous is a whitish shade that extends from the apex to the cell and a series of black dashes bordering it on the outward side, forming the upper part of the subterminal line. A separate pale spot is also located in cell M3. Males in general are very similar in size, color, and forewing pattern to the much more common Heterocampa obliqua . Forbes mentions that the pale spot in M3 has more of a bar shape in H. varia and a more of a circular shape in H. obliqua , but that difference is not apparent in our specimens. There may also be a difference in the adterminal line, which Forbes states is not arcuate in H. obliqua but appears to be fairly strongly arcuate in specimens we have examined. More reliable differences given by Forbes are seen in the hindwings: they are nearly pure white in H. varia , with only a dark anal spot and dark bars in the fringe, whereas in H. obliqua , there is usually a dark shade in the fold and a well-defined terminal line (Forbes, 1948). The basal area of the forewing and thorax may also be paler gray in H. varia than in H. obliqua , and H. varia lacks the greenish tint found in some specimens of H. obliqua . In most cases, these external differences are only slight and inspection of the 8th sternite offers the surest way of distinguishing the males of the two species (see Structural Features below). Females are usually more separable (Schweitzer et al., 2011): in H. varia , they have a coloration similar to the males whereas in H. obliqua , females usually have a strong brown shade located between the discal spot and pale apical shade. Forbes, however, points out that there are at least some forms of female H. obliqua that are similar to males and, by extension, similar to H. varia . Where this is true, the much darker hindwings found in female H. obliqua may distinguish them from H. varia , whose hindwings usually are fuscous only in the subterminal area and paler whitish towards the base.
Wingspan: 45-50 mm, males; 50-57 mm females (Forbes, 1948)
Adult Structural Features: Antennae of males are pectinate basally and simple at the apex; antennae of females are simple over their entire length. Males of varia differ from those of obliqua in both the genitalia and in the configuration of the 8th sternite, which can be easily seen by brushing away the scales on the underside of the tip of the abdomen: in obliqua, there is a conspicuous curved, indented line that connects the two sternal pits; in varia, no such indentation exists and the posterior edge of the sternite has two lateral lobes that are much better developed than in obliqua. The internal genitalic features also easily distinguish males of the two species, with pronounced differences in both the socii and aedeagus (see Forbes, 1948, for a description and illustrations).
Adult ID Requirements: Identifiable from photos showing hindwings, abdomen, or other specialized views [e.g., frons, palps, antennae, undersides].
Immatures and Development: Larvae are similar to those of Heterocampa obliqua. Early instars have thoracic "antlers" that are shed as they mature. Later instars have a smooth, pale green body with a pale dorsal stripe. Wagner (2005) describes varia as having the dorsal stripe much less constricted between two white saddles than in obliqua, with the constriction being about half as wide as the posterior saddle. A white triangle at the anterior of the body also extends forward across the top of the head in varia, reaching the antennae (a larva of varia is illustrated in Schweitzer et al., 2011).
Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants.
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