Papilio solstitius DeRoller, Wang, Dupuis & Schmidt, 2025, sp. nov.

Papilio solstitius sp. nov. Figs 3 a, 4, 5, 6 a, 7 a, 8 a, 9 c-d, 10 a, 11 Type locality. Canada, Ontario, Ottawa-Carleton District, Long Swamp, Old Almonte Rd., 45.249°N, 76.079°W. Type material. Holotype (Fig. 4 a) • male. Ontario, Ottawa-Carleton Dist., Old Almonte Rd. at Long Swamp, 45.249°N, 76.079°W, 3. Jul. 2020, B. C. Schmidt, CNC voucher # CNCLEP 00342771 [CNC]. Allotype (Fig. 4 b) • female. Ontario, Frontenac Co., Vanalstine Lake, 44.858°N, 76.847°W, 5. Jul. 2021, B. C. Schmidt, observed ovipositing on Prunus serotina [CNC]. Paratypes • 53 in CNC, 9 in XWC, 8 in CJDC; complete data and specimen deposition are given in Suppl. material 1. Etymology. The epithet solstitius is derived from solstitium, the Latin term for solstice. The species’ unique midsummer flight period commences near the summer solstice. Differential diagnosis. Papilio solstitius is closely related to P. glaucus, P. canadensis and P. appalachiensis, but differs from all in a suite of characters (Table 1). The most significant differences are apparent in developmental biology and phenology. Papilio solstitius is unique in its long post-diapause emergence delay, with adult eclosion beginning in late June to early July, compared to May for all other species (Fig. 2). Unlike the facultatively multivoltine P. glaucus, P. solstitius is obligately univoltine (like P. canadensis and P. appalachiensis). In the northern part of its range, P. solstitius overlaps with P. canadensis, and in the south with P. glaucus; it is not known to overlap with P. appalachiensis (Fig. 1). Identification difficulties are therefore largely limited to confusion with either P. canadensis or P. glaucus. In combination with location and date, the comparative morphological characters summarized in Table 1 and discussed in the “ Comparative Morphology ” section below will serve to identify most specimens. * based on images and information in Pavulaan (2024 a). Description of adult. Head (Fig. 3) and thorax: setation of frons of moderate length, intermediate between P. canadensis and P. glaucus; dorsum of head and thorax with limited sublateral yellow scaling; ventral thorax vestiture pale lemon yellow, legs black. Forewing (Figs 4, 5, 6): Male forewing length 50.7 mm (46.7–55.0 mm; n = 17), female 53.4 mm (47.7–57.0 mm; n = 8); dorsal ground color of male mustard yellow (Ridgway 1912), of female light orange yellow (Ridgway 1912), like that of P. glaucus but slightly richer in tone than P. canadensis; female mimetic dark phase absent; all pattern elements flat black; antemedial band an elongate wedge variable in thickness and edge, on average attenuating more strongly between Cu and anal margin than in P. canadensis; medial band an irregular rectangular bar across discal cell, variably extending as far as vein Cu 2 or slightly beyond (in P. canadensis the medial band is more extensive, more frequently extending past Cu 2 and sometimes to 2 A); subapical black bar well-defined in cell R 3 - R 4, diminishing across R 5 - M 1, more strongly so than in P. canadensis; costa and subapical bar with diffuse yellow streaking, generally more so than in P. canadensis; females with wider, more diffuse transverse black bands than males; marginal band solid black with 6–8 yellow rounded-ovoid submarginal spots in interspaces; pattern elements repeated on ventral forewing, but ground color paler yellow, and black elements of distal half of wing with a flush of yellow scales; submarginal band variable but comprised of essentially D-shaped yellow spots usually separated by black lines along veins; yellow spots wider and more confluent than in P. glaucus, but more discrete and irregular than the essentially continuous, even-bordered band of P. canadensis. Hindwing: (Figs 4, 5, 7): Like P. glaucus, the scalloping of the hindwing outer margin is more pronounced than in P. canadensis, as a result of the disc margins oriented closer to the perpendicular of the long axis of the hindwing; the tail and Cu 2 angle are slightly more lunate / lobate than in P. canadensis; ground color identical to that of forewing; inner margin bordered in black across 35–50 % of cell 2 A-Cu 2; narrow, straight medial line attenuating towards juncture with anal band near Cu 2; end of discal cell veins black-scaled; black marginal band extending along distal quarter of wing, with diffuse yellow dusting from vein M 2 to anal angle; yellow submarginal lunules in the four cell spaces between Rs and Cu 1; lunules of cell ScR 1 - Rs and Cu 2 - Cu 1 (i. e., the uppermost and lowermost lunules) reduced or absent, orange or orange and yellow when present; anal angle with orange crescent capped proximally with blue, black bordered crescent; males with diffuse blue crescent in cell Cu 1 - Cu 2, often faint, rarely traces of blue crescent in adjacent cell Cu 1 - M 3; females with more extensive blue scaling, often with diffuse crescents extending to costal edge of submarginal band; ventral hindwing paler than dorsum, and with dusting of yellow scales across marginal band, and with more prevalent orange scaling in submarginal lunules and basad of marginal band in cells M 3 -2 A; yellow setae along anal band shorter and sparser than in P. canadensis. Abdomen: dorsum black, pale yellow laterally and ventrally with black sublateral line; vestiture of mixed yellow and black fine, setae; scales of male clasper entirely yellow (Fig. 8); clasper of male valve with two dorsal tines (Fig. 9). Description of larva. First instar (Fig. 10) with well-developed white medial saddle, comprised of predominantly white dorsal pigmentation of segments A 3 - A 4; three additional, variably developed white bands, one each comprised of T 1 and T 3, and a posterior band formed by A 8; Anterior and posterior bands rarely absent (entirely brown pigmentation); mature larva (Fig. 11) indistinguishable from that of P. glaucus and P. canadensis. Comparative morphology of the Papilio glaucus - complex Adult morphology of all eastern North American species in the glaucus - complex can be deceivingly similar, and any single morphological character should not be relied upon for identification. Most similar to P. solstitius are P. glaucus, P. canadensis and potentially P. bjorkae, another new species in the glaucus - complex proposed in 2024 (Pavulaan 2024). Given its recency, the taxonomic status of P. bjorkae has not yet been scrutinized by the scientific community, but it is necessary to do so here. For the reasons detailed below the recognition and diagnosis of P. bjorkae is currently problematic, although based on the spring flight period and comparison of the figures in the original description (Pavulaan 2024), it is certain the name does not apply to MST. The justification for treating P. bjorkae as a distinct species hinges on recognition of three distinct, partially sympatric, spring-flying taxa, recognized by adult phenotypes (P. glaucus, P. “ near canadensis, ” P. bjorkae) which correlate with slightly different flight periods (Pavulaan 2024). No diagnostic differences in immature stages, biology, larval hosts, or molecular markers of P. bjorkae have been documented to date (Pavulaan 2024), nor is there evidence in previous research that might hint at the existence of such (e. g., Ording et al. 2010; Kunte et al. 2011). Using seasonal adult abundance peaks combined across the glaucus - complex, flight phenologies for taxa present within the range of P. bjorkae are attributed to spring (P. glaucus, P. canadensis, and P. bjorkae), summer (midsummer swallowtail), and late summer (second-generation P. glaucus) (Pavulaan 2024: figs 3–5). During spring (May through June), P. bjorkae flies in “ late spring, ” versus “ early spring ” for P. glaucus and P. canadensis. However, only a single spring abundance peak is evident and attributed to P. bjorkae, whereas neither P. glaucus nor P. canadensis peaks are distinguishable due to the relative scarcity of observations for these species (Pavulaan 2024: 7, figs 3, 4). No additional data are provided to define late- versus early spring, leaving it unclear to what extent the phenology of P. bjorkae differs. Life history data that could corroborate such a difference are currently lacking. The differential diagnosis of P. bjorkae is based largely on differences in wing pattern and shape, especially of the female (Table 1). Males are described as intermediate between P. glaucus and P. canadensis; comparative differences are given compared to P. appalachiensis and P. canadensis, but not P. glaucus (Pavulaan 2024: 16). Without an indication of sample size and a full description of male and female morphology, it is currently difficult to gauge intra- versus interspecific variation. Lastly, P. bjorkae is stated to be larger than spring P. glaucus and P. canadensis, but conflicting information on p. 9 states that P. glaucus is the largest species in the study region. No size measurements specific to male or female are given for P. bjorkae (including the holotype), nor is it possible to infer size of specimens from figures since scale bars are not given; size as a diagnostic trait for P. bjorkae therefore remains undefined. The adult phenotype of P. bjorkae is very similar to that of P. canadensis and P. glaucus, so attributing phenotypic variation to three different putative taxa requires careful assessment. A potential additional source of phenotypic variation which remains unstudied stems from seasonal polymorphism in P. glaucus. Contrary to the assumption that P. glaucus is obligately bivoltine at the northern range edge (Pavulaan 2024), Ryan et al. (2016) demonstrate that it can be uni- or bivoltine depending on thermal constraints. In other words, temperature and day length experienced during the larval stage of P. glaucus dictate whether or not pupae develop directly into second generation adults, or enter winter diapause to emerge the following spring (Ryan et al. 2016). Since adult phenotype of P. glaucus is in

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