Thereus tiasa (Hewitson)

Faynel, Christophe, Huertas, Blanca, Crom, Jean-François Le, O’Brien, Richard & Fåhraeus, Christer, 2025, Diagnostic male secondary sexual structures and wing patterns in the Thereus genena species group (Lepidoptera: Lycaenidae: Theclinae) with the description of nine new species from Colombia, Peru, Brazil and French Guiana, Zootaxa 5728 (2), pp. 201-246 : 218-220

publication ID	https://doi.org/10.11646/zootaxa.5728.2.1
publication LSID	lsid:zoobank.org:pub:2E6171E0-E7A7-430E-BCC0-2C583209A94F
persistent identifier	https://treatment.plazi.org/id/F8303331-AF03-EA33-ABEF-FF0C9A49EAD5
treatment provided by	Plazi
scientific name	Thereus tiasa (Hewitson)
status

Treatment

Figures 18, 19, 20 View FIGURES 18–22 , 39 View FIGURES 34–49 , 55 View FIGURES 50–59 , 71 View FIGURES 66–77 , 89 View FIGURES 88–89

Thecla tiasa : Hewitson: 1869: (4): 122

= Thecla buris : Druce: 1907: (3): 590

Type material. The original description of Thecla tiasa by Hewitson is based on at least one female present in his own collection and coming from “Amazon”. However, Kirby (1879) did not list this specimen in his catalogue of Hewitson’s collection. Druce (1907) confirmed that the female was “stated by Hewitson to be in his own collection but is now not there”. This could mean that the specimen examined by Hewitson for his description was either moved or it was not part of his own collection, which he mistakenly claimed.

Three elements in the original description of Thecla tiasa can help finding specimens of the type series: the diagnostic characters of both sides of the specimen (text and drawing) and its wingspan. Unfortunately, the dorsal side is not useful because the characters cited by Hewitson ‘rufous-brown with scarlet anal lobe and submarginal line of white’, could apply to several female species of the genena group. The description of the underside provides more interesting diagnostic elements which are underlined: “UNDERSIDE rufous. Both wings crossed beyond the middle by a band of brown bordered outwardly with white, with an unusual bend at the middle of the posterior wing, and ending above the anal angle in a semicircle: both with a very indistinct submarginal band of brown: the lobe and a triangular black spot between the tails broadly bordered above with scarlet: a submarginal white line, the margin black”. Hewitson mentioned the two VHW red-orange spots but does not say if there are red scales between them (in CuA 2 -2A) but the original drawing shows that the two spots are linked by red scales. Lastly, the dimensions mentioned an “expanse” (wingspan) of “1 4/ 10 inch ” or 35.56 mm.

NHMUK015200801 NHMUK015201058 NHMUK015201062 NHMUK015201063

specimen 1 specimen 2 specimen 3 specimen 4

We found four potential syntypes in NHMUK ( Figs 11 View FIGURES 2–17 , 19, 20, 21 View FIGURES 18–22 ) and we have the whole genome extracted for each of them. Table 2 summarizes the comparisons made.

The first specimen bears a type label and was stored in the NHMUK type collection under the name T. tiasa ( NHMUK 015200801, Fig. 21 View FIGURES 18–22 , called specimen 1 in the text for clarity), which means that somebody in the past has identified it as a syntype of T. tiasa . The circular label “ Para ” attached to specimen 1 is an old BMNH label which usually meant specimens coming from Belém or Pará and collected by either Bates or Wallace (Lamas, pers. comm.). Although there are occasions where Hewitson would include Pará under the umbrella term “Amazons”, this would only be when he had specimens from multiple regions of the Amazon forest. When he had only one specimen labelled from a specific place in the Amazons, Hewitson wrote in the text the exact place mentioned on the labels like for Thecla genena : “In the Collection of H. W. Bates, from the Amazon ( Pará)” and for Thecla endera : “In the Collection of the British Museum, from the Amazon (Ega)” and both of them have labels from respectively Pará and Ega. Moreover, specimen 1 wing patterns don’t fit well with the original description and drawings: the VHW postmedia n line is straight (no bend at the middle), there are very few red-orange scales in CuA 2 -2A and the wingspan is much smaller ( Table 2). Although it was labelled as type, specimen 1 is probably not the one used for the description of T. tiasa .

An alternative female specimen which corresponds to the original description has been found in the general collection ( NHMUK 015201058, Fig. 11 View FIGURES 2–17 , called specimen 2 in the text). It is from the Godman & Salvin’s collection, has a handwritten label reading “Tiasa ” [sic], and a locality label “Amazons”. Its wing pattern has the characteristic of the original description of T. tiasa (VHW postmedian line bent at the middle, red-orange scales in CuA 2 -2A) except a smaller wingspan ( Table 2). In conclusion, this specimen represents a possible syntype of Thecla tiasa with less ambiguity than the previous one. The whole genome analysis shows it represents the female of T. genena as we previously wrote. T. genena and T. tiasa were described in the same publication, in this order.

A third female was found in the NHMUK main collections ( NHMUK 015201062, Fig. 20 View FIGURES 18–22 , called specimen 3 in the text) with “tiasa ” written on the reverse of one label. Another label indicates it comes from “Ega, U. Amazons” contrary to Hewitson’s description. Although VHW has red-orange scales in CuA 2 -2A, there are some discrepancies like the wingspan much smaller and the VHW postmedian line almost straight. Like specimen 1, it is unlikely that specimen 3 was the one used by Hewitson for the description of T. tiasa . The full genome analysis shows it represents the same taxa as the male holotype of T. buris , a species described later. Robbins (2004) considered T. buris as a synonym of T. tiasa .

We found a last female specimen ( NHMUK 015201063, Fig. 19 View FIGURES 18–22 , called specimen 4 in the text) among the T. genena material in the NHMUK general collection. It matches well the original description and drawings: a VHW postmedian line bent at the middle, red-orange scales in CuA 2 -2A and it is the largest of the four specimens, with approximately the same wingspan as in the original description ( Table 2). Moreover, it is labelled with both “tiasa ” and “Amazon”. The two elements that don’t correspond are a VHW postmedian line above the anal angle which is more V than U-shaped, and it comes from the Godman & Salvin’s collection, originally collected by Bates. The full genome analysis shows it represents also the same taxa as the male holotype of T. buris .

Neotype designation. It is necessary to define the nominal taxon Thecla tiasa objectively. No unambiguous specimen in NHMUK seems to belong to the original type series, thus we have to designate a neotype (Art. 75.1.). Historical specimens are potential candidates (Recommendation 75A). Specimens 1 and 3 have too many elements that don’t match with T. tiasa original description to be chosen. Specimen 2 is a good candidate, but it will mean that Thecla tiasa will become a junior synonym of T. genena contrary to what has been established in the literature before (D’Abrera 1995, Robbins 2004). For stability, it is better not to choose this specimen. Specimen 4 is an appropriate candidate for being designated as neotype of Thecla tiasa for the reasons stated before and it is in taxonomic accord with the prevailing usage of both Thecla tiasa and Thecla buris names ( Robbins 2004). Consequently, we will designate the female stored in NHMUK ( Fig. 19 View FIGURES 18–22 ) as neotype of Thecla tiasa .

NEOTYPE ♀ ( Fig. 19 View FIGURES 18–22 ) designated here: “ ♀ ” (brown rectangular label, printed); “ ♀ //Amaz.” and “tiasa .” written on the back of the label (two brown rectangular labels stuck together in a cross formation, handwritten); “Amazons. // H.W. Bates.” (brown rectangular label, printed); “Godman-Salvin // Coll. 1911.-93.” (brown rectangular label, printed); “Gen. prep. K. Florczyk // NHMUK015201063” (green rectangular label, black printed); “ Thecla tiasa // Hewitson, 1869 // NEOTYPE // Faynel, 2025 ” (white rectangular label, printed); “NHMUK015201063” (white rectangular label, printed, with a flash code).

Other type material examined. SYNTYPE ♂ Thecla buris ( Fig. 18 View FIGURES 18–22 ): “ Syn- // type” (blue rimmed white circle label, printed); “Type” (orange rimmed white circle label, printed); “Ega, // U. Amazons. // H.W. Bates.” (brown rectangular label, printed); “ ♂ ” (brown rectangular label, printed); “ ♂ Ega”, “genena .” (two brown rectangular labels stuck together in a cross formation, handwritten); “ T. buris ♂ // TYPE H.H. Druce” (brown rectangular label, handwritten); “Godman-Salvin // Coll. 1911.-93.” (brown rectangular label, printed); “B.M. TYPE // No.Rh.727” (brown rectangular label, printed and handwritten); “ Thecla buris // H.H. Druce, 1907 // SYNTYPE ” (white rectangular label, printed); “NHMUK015200785” (white rectangular label, printed, with a flash code); “Gen. prep. K. Florczyk // NHMUK010402976” (green rectangular label, black printed).

SYNTYPE ♀ Thecla buris : “ SYN- // TYPE” (blue rimmed white circle label, printed); “Type” (orange rimmed white circle label, printed); “ ♀ ” (brown rectangular label, printed); “Tapajos, // Amazons. // H.W. Bates. ” (brown rectangular label, printed); “ ♀ Tapajos”, “ genena ” (two brown rectangular labels stuck together in a cross formation, handwritten); “ ♀ ” (brown rectangular label, handwritten), “ T. buris ♀ // TYPE H.H. Druce ” (brown rectangular label, handwritten); “Godman-Salvin // Coll. 1911.-93.” (brown rectangular label, printed); “ Thecla buris // H.H. Druce, 1907 // SYNTYPE ” (white rectangular label, printed); “NHMUK015200778” (white rectangular label, printed, with a flash code). Not belonging to the same species (see remarks below) .

Other material examined ( 3♂, 1♀). Peru. Loreto . 1♂, Tamshiyacu, 100m, xi.2013, CF-LYC-710* ( RCCF) .

Brazil. Amazonas. 1♂, Ega [=Tefé], Rothschild Bequest B.M. 1939-1., NHMUK015201101*, gen. prep. K. Florczyk ( NHMUK) . 1♀, Ega [=Tefé], Upper Amazons. H. W. Bates, Godman-Salvin Coll., gen. prep. K. Florczyk 010402976, NHMUK015201062* ( NHMUK, illustrated on Fig. 20 View FIGURES 18–22 ) . No Locality. 1♂, 20/2, Brazil Ex Coll. Smith. 1844-5, NHMUK015201045, gen. prep. K. Florczyk ( NHMUK) .

Diagnosis and description. Thereus tiasa can be distinguished from all the other species of the genena group by a unique triangular dark brown scent patch in the male discal cell ( Fig. 39 View FIGURES 34–49 ). It is surrounded by bluish-grey scales and adjacent to the scent pad. The closest species in the ML tree is T. genena which has 2.75% mean genetic divergence. We have not found reliable wing characters to distinguish the females of T. tiasa from those of T. genena . Male genitalia ( Fig. 55 View FIGURES 50–59 ). Four males dissected, including the syntype of Thecla buris . Dorsal brush organs longer and processes supporting them closer to saccus compared to previous species. Penis straight. Eighth tergite subrectangular with convex anterior border and posterior one almost straight. Female genitalia ( Fig. 71 View FIGURES 66–77 ). Two females dissected, including the neotype. Ostium bursae angled 130° with ductus bursae. No sclerotized element observed on the membrane in between the papillae anales. Eighth tergite subrectangular with convex anterior border and concave posterior one.

Sympatry. Thereus tiasa is sympatric with T. genena .

Known distribution ( Fig. 89 View FIGURES 88–89 ). Peru (LOR). Brazil (AM).

Remarks. According to ventral wing pattern, the female syntype of Thecla buris represents another taxon. Both syntypes of Thecla buris have one of their labels written ‘ genena ’ at the reverse. This shows the confusion that existed in this group about the identity of very similar species. The character used in the original description for the VHW postmedian line “unusual bend at the middle of the posterior wing” is variable with two females checked by DNA as T. tiasa ( Figs 19, 20 View FIGURES 18–22 ) that have different VHW postmedian line curvature.