Catocala insolabilis is easily distinguished from other dark underwings occurring in the province (C. obscura Strecker, C. judith Strecker, C. retecta Grote, and C. residua Grote) by its ventral side which is predominantly black with some white near the basal area (Ishizuka 2011). The postmedial band on forewings is largely absent, and very narrow and obscure on hindwings (Sargent 1976). Catocala insolabilis can also be easily distinguished from Catocala maestosa Hulst, which could be expected to occur in the province in the upcoming years due to its similar geographic distribution and ecological niche; C. insolabilis lacks a white fringe on the hindwings, and the underwings exhibit bands that may appear faint or absent, with a notable gray basal area (Sargent 1976). In contrast, C. maestosa hindwings are a deep black color a with heavy dusting of contrasting light gray hairs at base (Sargent 1976).

The four specimens of C. insolabilis sampled in Quebec were significantly damaged, suggesting that they were long-distance dispersers that did not emerge at the collection sites. Given the regular surveys at the sites by amateur entomologists, the collecting of fresh specimens over the years of sampling would have been very probable if the species was established. It is possible that C. insolabilis has not yet established in the province due to its low abundance and fragmented habitats. As of now, its distribution is known to range from southern Ontario, Canada, to Florida, United States, occurring in most of the Eastern United States. The occurrence of the species in Quebec is surprising, considering that it only has occurrences in southernmost Ontario and none in the adjacent State of Vermont (Hess & Hanks 1979; Hanks 1995; GBIF 2023). The species is considered rare in the northern part of its distribution and uncommon in the south because it is largely associated with its hosts, hickories (Carya spp.), as are several other rare underwing species (Handfield 2011). However, C. insolabilis has been reported as locally common in Florida, where it preferably feeds on pignut hickory (Carya glabra (Mill.) Sweet) (Wagner et al. 2011). Carya glabra is not present in Quebec and there does not seem to be other reports of specific hickory species that C. insolabilis would prefer (Robinson et al. 2023). Nevertheless, the three sites where the species was sampled in Quebec were forests where several mature bitternut hickories (Carya cordiformis (Wangenh.) K.Koch) and shagbark hickories (Carya ovata (Mill.) K.Koch) are present. These findings highlight the importance of the rare and fragmented habitats harboring mature hickory trees in the south of the province of Quebec and emphasize the relevance of citizen science for monitoring biodiversity.