Cheimas Staudinger

Pyrcz, Tomasz W., Lorenc-Brudecka, Jadwiga, Boyer, Pierre & Zubek, Anna, 2018, Subspecies-level systematics and affinities of Cheimas Thieme - an endemic genus of the subparamo of the Venezuelan Cordillera de Mérida (Lepidoptera: Nymphalidae, Satyrinae), Zootaxa 4422 (2), pp. 219-243 : 221-222

Cheimas Staudinger

Type species: Oxeoschistus opalinus Staudinger, 1897: 145 –146, by original designation.

Generic diagnosis. Adults of this genus can be identified immediately by the rounded or oval greenish blue patch on the hindwing dorsum. Such a colour pattern is nearly exclusive to Cheimas among neotropical Satyrinae , and the only species with a somewhat similar bluish patch is Mygona irmina (Doubleday) which however has a completely different wing shape with scalloped hindwing margin, which is smooth in Cheimas , and a forewing distal margin produced below the apex, smooth in Cheimas . Several species of Lasiophila C. Felder & R. Felder , and one of Steromapedaliodes Forster have bright, oval hindwing patches but these are invariably snowy white, and additionally Lasiophila have hindwing tail-like extensions along vein CuA1, absent in Cheimas .

Redescription. Head: Antennae composed of 32 flagellomeres (based on 10 specimens representing all the subspecies), orange brown, naked, except some sparse scales on basal segments, club composed of 9 flagellomeres, slightly flattened, dorsally blackish–brown; eyes chocolate brown, densely hairy covered with black setae; labial palpi 2.5 the length of head, covered with thick hairy scales, dorsally sandy yellow, ventrally black, brown and chestnut. Thorax: black, covered with golden brown hair on the sides, in the middle mostly naked except for some tiny dark blue scales. Legs brown, covered with rather sparse sandy yellow scales and hair. Wings: Shape: FW triangular with a subacute apex and a slightly concave outer margin; FW rounded with delicately undulated margins; Venation ( Fig. 12): FW vein R2 arising separately from R3+R4+R5; cross vein r–M1 short but present; cross vein m1–m2 well incurved basally; vestigial discal–cell veinlet present. HW humeral vein present; cross vein m1–m2 four times longer than rs–m1 and incurving basally at a sharp angle; A1 and A2 separate along their entire length; Colour patterns: Dorsal FW and HW ground colour brown or chestnut; a bluish or greenish HW median patch, rounded or oval; Ventral FW mostly reddish brown with faint postdiscal and submarginal lines; HW ground colour highly variable, between dusty yellow and reddish brown with a pattern of irregular median, postdiscal and submarginal lines, and in some populations a sandy yellow discal spot. Abdomen: Male genitalia: Simple, characterized by a long and stout uncus, long subunci, longer than half the length of uncus, narrow and uplifted, elongated and rather slender valvae with a blunt apex and slightly irregular dorsal surface occasionally produced in the form of a short process, a rather deep saccus and aedeagus straight or slightly arched, about the length of valvae, smooth. Female genitalia: Papillae anales large; apophysis posterior short but present; a spatiose membraneous pocket enclosing antrum; paddle–like antevaginal and postvaginal lamellae; ductus bursae of intermediate length and width as compared to other genera of Pronophilina , straight, with an internal sclerotized slat; corpus bursae oval or rounded without signa (see: Pyrcz et al., 2011; 2017).

Subspecies discrimination. We identified five geographically well–defined and morphologically discrete subspecies of Cheimas opalinus , described below, differing from each other mostly by their dorsal colour patterns, in particular the shade of the brown ground colour, and colour and shape of the hindwing upperside greenish-blue patch. The entire FWD and most of the HWD of C. opalinus is uniform brown, however the shades of brown varying between chestnut and blackish–brown are valuable taxonomic characters. The HWD median patch is the only conspicuous feature varying between steely blue and shining green. The shade can be very useful in helping to distinguish between the subspecies, but considerable caution is needed. The scales that make up the patch have a tendency to fall away, particularly in ageing individuals. It leads to the alteration in the colour of the patch, and with time blue shades tend to prevail over light green. Eventually, some individuals may even lose completely their blue scales, more frequently in the females. Therefore, the descriptions of the subspecies is based on freshly emerged specimens exclusively, although the characters diagnostic for each subspecies are evident even in older, worn specimens in most cases.

Ventral colour patterns are fairly variable among subspecies, especially on the HW. For example, the individual form spoliatus is characterized by the lack of any white pattern on the HWV. HWV pattern can be light and dull in some specimens, heavily suffused with blackish scales and contrasting in others. HW postmedian and submarginal lines can take different shapes as well. FWV ground colour, varying between orange brown and dark brick red is somewhat more stable and specific to given populations, and can be used, with some restriction as a taxonomic character.

The various subspecies of Cheimas opalinus also differ in size and, to some extent in wing shape, which can be appreciated based on long series of examined individuals from different populations. These are valuable taxonomic characters that have been taken into consideration in defining the subspecies. Sexual dimorphism in the subspecies of C. opalinus is little marked and limited to the slightly larger size of the female, lighter dorsal ground colour, paler and less patterned HWV, and more undulated HW margin.

Male and female genitalia also provide some taxonomic information, even if the differences between the subspecies are slight and mostly quantitative affecting the proportions of sclerites and, to some extent, their shape, rather than the presence or absence of morphological structures. Male genitalia differ between the subspecies mostly in the shape of valvae and the size of the subapical dorsal process, and those of female genitalia in the width and length of ductus bursae and shape of processi at the entrance of the antrum. Subspecific differences between female genitalia are more pronounced than between male genitalia.