Rasahus myrmecinus ( Erichson, 1848 ) Swanson, 2018

Swanson, Daniel R., 2018, Three new species of Rasahus, with clarifications on the identities of three other Neotropical corsairs (Heteroptera: Reduviidae: Peiratinae), Zootaxa 4471 (3), pp. 446-472 : 459-467

Rasahus myrmecinus ( Erichson, 1848) stat. rev. et comb. nov.

( Figs. 8 , 9 , 10A , 11A–B )

Pirates myrmecinus Erichson, 1848: 613 .

Rasahus scutellaris (nec Fabricius, 1787): Champion, 1899: 215, 218.

Coloration: Blackish, except apical spine of scutellum, apical half of clavus, adjacent part of corium from base to apex of clavus (with small interruption at midway), three spots on hemelytral membrane (ovoidal spot near base, narrow arcuate spot near apex of corium, and ovoidal spot at apex), anterior two-thirds of connexiva (dorsally and ventrally, with adjacent part of ventrite), base of trochanter and metafemur whitish. Tarsi and fossula spongiosa brownish. Head and pleura laterally with metallic blue-black tint.

Structure: Anteocular region covered on all surfaces with short silvery pile, laterally with few long setae. Interocular region with width 1.5 times width of eye in male, 1.3 times width of eye in female, with silvery pile dorsally. Postocular region with short longitudinal sulcus reaching cephalad from transverse sulcus. Neck appearing glabrous.

Antennae: as per description under Rasahus .

Eyes in lateral view surpassing dorsal margin and nearly reaching ventral margin.

Ocelli large, slightly raised on inconspicuous tubercle, separated from each other by twice width of one ocellus in male and 1.5 times width in female, separated from eye by slightly more than width of one ocellus in both but slightly more distant in male.

Rostrum: as per description under Rasahus .

Pronotum: Anterior pronotal lobe with sulci present and hirsute, integument of sulci with inconspicuous granules, short and long setae in sulci, deep foveolar sulcus on midline in front of transverse suture. Posterior pronotal lobe with long wrinkles emanating from transverse suture, lots of setae along lateral and posterior regions.

Scutellum with minute granules, with long and short pile on disc, apex prolonged in dorsally-setose spine.

Pleura: Propleuron smooth. Metapleuron slightly transversely wrinkled, glabrous, metapleural sulcus wide between carinae.

Sterna: Metasternum evenly convex, slightly pustulate.

Hemelytra slightly but distinctly exceeding abdominal apex in male, not but nearly reaching apex in female, veins of corium bearing semi-erect setae.

Forelegs: Profemur with ventral setae arranged in two rows. Protibial fossula spongiosa present, about halflength of tibia.

Middle legs: Mesoibia generally more pilose and with fewer distinct dorsal setae, mesotibial fossula spongiosa relatively shorter, slightly less than one-third length of tibia, more densely setose ventrally. All else as forelegs.

Hind legs: Metatibia densely setose apicolaterally although less so in female. All else as middle legs.

Abdomen connexiva with long thin seta at posterolateral angle, sutures poorly indicated, third ventrite also carinate medially in male. Apex of seventh ventrite strongly pilose.

Male genitalia: Eighth ventrite extended caudad as median triangular spine. Pygophore sparsely pilose, posterior margin concave between median process and base of parameres, median apical process tall, strongly sinuate (left margin strongly curved, right margin weakly so), broad and bent sinistral in basal half, curving dextral in apical half, apex broadly triangular with acute point. Parameres large, asymmetrical, both spade-shaped and with apices acutely rounded, densely pilose on outer surface, left paramere slightly larger, basal lobe more shallow, with attenuated, mesally-bent, somewhat flattened apex, right paramere slightly broader, deeply lobate with greatest width skewed to basal-third, with non-attenuated tectiform apex. Aedeagus not examined.

Female genitalia: Of general peiratine form. Visible portion of eighth tergite short, posterior margin convex. Ninth tergite trapezoidal. Tenth tergite trapezoidal, apices subrounded. Lobes of valvifer 1 (= part of eighth segment) hemispherical. Valvulae 1 somewhat elongate, convex apicolaterally, apex roundly acute. All segments with integument smooth (except few rugulae ventrally on valvifer 1), lacking spines or tubercles, with abundant short pale appressed pubescence and sparse scattered long semi-erect setae. Tenth tergite with long golden setae of moderate length, more densely so along lateral and apical margins.

Measurements (in mm): total length (apex of head to apex of hemelytra): male: 11.2, female: 11.7; head length: 1.6; head width (across eyes): male: 1.5, female: 1.6; anteocular length: male: 0.6, female: 0.7; postocular length: 0.3; neck length: 0.7; scape length: male: 0.9, female: 1.0; pedicel length: male: 2.4, female: 2.3; basiflagellum length: [male: 2.4, female: 2.1; distiflagellum length: male: 2.4, female: 2.1; antennal segment ratio: 1.0: 2.5: 2.3: 2.3; eye length: 0.4; eye width: 0.3; rostral segment 1 length: 0.6; rostral segment 2 length: 0.9; rostral segment 3 length: 0.5; rostral segment ratio: 1.0: 1.5: 0.8; prothorax length: male: 2.5, female: 2.6; prothorax width (across humeri): male: 2.8, female: 3.0; anterior pronotal lobe length: 1.6; posterior pronotal lobe length: male: 0.9, female: 1.0; scutellum length: male: 1.4, female: 1.5; scutellum width (at base): male: 1.3, female: 1.5; hemelytra length: male: 7.5, female: 8.0; procoxa length: 1.4; protrochanter length: 0.7; profemur length: 2.6; protibia length: male: 2.2, female: 2.4; protibial fossula spongiosa length: male: 1.1, female: 1.0; protarsi length: male: 1.2, female: 1.3; protarsal segment ratio: 1.0: 1.8: 2.5; mesocoxa length: 0.7; mesotrochanter length: 0.7; mesofemur length: male: 2.4, female: 2.8; mesotibia length: male: 2.3, female: 2.7; mesotibial fossula spongiosa length: male: 0.7, female: 0.8; mesotarsi length: male: 1.2, female: 1.4; mesotarsal segment ratio: male: 1.0: 2.0: 2.0, female: 1.0: 2.1: 2.3; metacoxa length: male: 0.7, female: 0.8; metatrochanter length: male: 0.6, female: 0.7; metafemur length: male: 3.9, female: 4.0; metatibia length: male: 4.2, female: 4.4; metatarsi length: 1.8; metatarsal segment ratio: male: 1.0: 2.6: 3.0, female: 1.0: 2.3: 2.3; abdomen length: male: 5.6, female: 6.2; abdomen (widest) width: male: 3.1, female: 3.8; pygophore length: 1.5; pygophore width (across widest point): 0.9.

Material examined: BELIZE: Toledo District, Midway Village, collected under bark, 16° 07.3"N, 88° 57' 37.3"W, 16–17 July 2005, P. W. Kovarik, det. D. R. Swanson 2017 [1 male, 1 female] ( UMMZ) .

Distribution: Belize, Panama, Guyana.

Remarks: The specimens on which this redescription is based were initially identified as Rasahus scutellaris , then placed in an undescribed genus owing to conspicuous differences in the length of the protibial fossula spongiosa, the length and segmental ratio of the protarsi, and the metapleural sulcus. These morphologies match those found in Pirates myrmecinus , as observed in images of the holotype (despite the missing abdomen, the sex of the holotype of Pirates myrmecinus appears to be male, based on the thickness of the protibia compared with the Belizean male and female) ( Fig. 9 ). These discrepancies with the generic diagnosis or, in the very least the protibial fossula spongiosa, seem to have gone unnoticed by Coscarόn (1983a), as she purportedly examined Erichson’s holotype.

The length of the protibial fossula spongiosa is the most conspicuous morphological difference between Pirates myrmecinus and species of Rasahus . In both the male and the female from Belize, the fossula spongiosa covers at most half of the length of the protibia ( Fig. 10A ). The protibial fossula spongiosa also appears to be a similar length in Erichson’s holotype ( Fig. 8D ). This contrasts other species of Rasahus , which have the protibial fossula spongiosa occupying three-fourths of the tibial length ( Fig. 10B ). The state of this character is heavily relied upon for segregating peiratine genera (e.g., Stål 1872, 1874; Villiers 1948; Gil-Santana & Costa 2003). However, some genera well-delimited by other morphologies (i.e., Sirthenea Spinola, 1837 ; Tydides Stål, 1866 ) are known to possess limited degrees of intrageneric variation in the length of the protibial fossula spongiosa ( Willemse 1985, Lent 1955, Lent & Jurberg 1967). Among the known species of Rasahus , this is the only known case of such variation.

The protarsi differ markedly as well. In the Belizean specimens, the protarsi are long, being 1.2–1.3 mm, with a relatively longer apical tarsomere (segmental ratio: 1.0: 1.8: 2.5) ( Fig. 9C, F ); again, this is present in the Erichson’s holotype ( Fig. 8D ). This contrasts the ratio in some similar-sized Rasahus , such as R. abolitus sp. nov. ( Fig. 10B ) and R. nesiotes sp. nov., in which the penultimate and ultimate tarsomere are subequal (segmental ratio: 1.0: 1.6: 1.6) and the protarsi are shorter, being only 0.6 mm (other appendages remain similar in size). However, the segmentation ratio of the protarsi differs interspecifically in ways previously unappreciated; for example, R. deliquus sp. nov., despite being much larger, shares a similar ratio with the Belizean specimens. Additionaly, the metatarsal ratios also vary, with the second tarsomere being the longest in R. abolitus sp. nov. and R. nesiotes sp. nov., whereas the second and third tarsomere are subequal in R. deliquus sp. nov., and R. setosus , as well as the Belizean specimens. Tarsal differences have been used to delimit genera in Peiratinae (i.e., Fusius Stål, 1862 : Villiers 1948); yet, further study is needed to assess the utility of this variation in Rasahus and related genera.

Lastly, the form of the metapleural sulcus has been an important character for generic diagnoses, albeit exclusively for New World taxa. Most genera, including Rasahus , possess a curved marginally-positioned metapleural sulcus. However, in the Belizean specimens, the sulcus appears wider and the anterior end starts higher on the metapleuron ( Fig. 11A, B ) than in examined species of Rasahus ( Fig. 11C–G ) and other genera ( Fig. 11H, I ). Despite being out of focus, this appears to be the form of the sulcus in Erichson’s holotype too ( Fig. 8E ). However, this structure has largely been characterized bimodally (straight/medially-positioned vs. curved/laterallypositioned), and it remains questionable to what extent this character varies in other peiratine genera.

The color pattern of the Belizean specimens strongly mirrors that of R. abolitus sp. nov. However, it is true that a similar color pattern, viz. postscutellar spot + median corial discal spot + apical corial marginal spot + apical membranal spot, is found in multiple species of Rasahus (e.g., R. brasiliensis , R. castaneus ; R. sulcicollis ), and small variations thereof are found in other genera of New World Peiratinae (e.g., Phorastes , Tydides ). Vestiges of the postscutellar spot and spot of the hemelytral cubital cell are visible in Erichson’s damaged holotype ( Fig. 8B ). Additionally, the metallic atrocyaneous tint of the head and pleura in the Belizean specimens is absent in the similarly-patterned R. abolitus sp. nov., although metallic tints are known in other species of Rasahus , i.e., R. maculipennis , as well as other New World genera (i.e., Phorastes Kirkaldy, 1900 ). In Erichson’s holotype, the metallic tint is not conspicuous, given the low level of lighting, but it is plausible that it is present. The Belizean male and female match in color pattern, although this leaves the level of intraspecific variation completely unknown.

The generic placement of Pirates myrmecinus thus becomes clear. Rasahus is the only described genus to which P. myrmecinus might belong, based on keys in Gil-Santana & Costa (2003), Cai & Taylor (2006), and Gil- Santana et al. (2015). As the tarsal ratios vary intragenerically and the metapleural sulcus differs only in minor degree, only the length of the protibial fossula spongiosa is found to differ markedly from other species of Rasahus . As a few other genera in the New World show intrageneric variation in this character, I have refrained from erecting a monotypic genus for a species that shows such strong similarity to as speciose and potentially morphologically variable a genus as Rasahus .

Regarding its specific identity, Pirates myrmecinus Erichson, 1848 , remains distinct. It clearly differs from Rasahus scutellaris stat. rev. in size, length of the anteocular region, and hemelytral color pattern; therefore, it is resurrected from synonymy (stat. rev.) and transferred, becoming Rasahus myrmecinus ( Erichson, 1848) comb. nov. Rasahus myrmecinus stat. rev. et comb. nov. is easily diagnosed among its congeners by the small size (10– 13 mm), the color pattern (atrocyaneous tint of the head and pronotum and postscutellar spot + median cubital spot + apical corial marginal spot + apical membranal spot), and the protibial fossula spongiosa occupying only half of the length of the protibia in both sexes. The external genitalia of the male are distinctive in the strongly-bent, moderately-broad median process of the pygophore ( Fig. 5G–I ); it is somewhat similar in the median process to R. setosus (but differs in many other characters) and very similar in both process and parameres to R. scutellaris auct. figured by Coscarόn (1983a). Additionally, the generic diagnosis of Rasahus has been modified to include species with the protibial fossula spongiosa occupying half or more the length of the protibia.

A final note: the erection of R. abolitus sp. nov. and the revised status of R. myrmecinus stat. rev. et comb. nov. almost completely confound records of Rasahus scutellaris auct. (nec Fabricius). Only those specimens collected and examined by Champion (1899) from Bugaba District, Panama seem to belong unambiguously to R. myrmecinus stat. rev. et comb. nov., as he mentioned the the aeneous coloration, short protibial fossula spongiosa, long apical metatarsomere, and small size. It seems likely that some records of other authors might apply to the former and some to the latter, given the strong similarity in habitus and the probable overlap in geographic distribution. Furthermore, it is unclear whether Coscarόn’s (1983a) description of R. scutellaris corresponds to R. abolitus sp. nov. or R. myrmecinus stat. rev. et comb. nov., as both are small (10–13 mm), similarly-patterned species known from Central America and/or northern South America, although it seems more likely that the description corresponds to the latter, given the obsolete condition of the pronotal sulci and granules in R. abolitus sp. nov., as well as a few genitalic details. Regardless, a careful inventory and re-evaluation of previous records will be needed to disentangle the distributions of these species. Currently, R. abolitus sp. nov. is known only from the type locality in French Guiana and R. myrmecinus stat. rev. et comb. nov. is known from Guyana (type locality), Panama ( Champion 1899), and Belize (present study).

Key to species of Rasahus and Froeschnerisca . The following key will facilitate separation of the species included in Rasahus and Froeschnerisca . This key is more reliant on color pattern, as differences in the macular pattern of the hemelytra are more conspicuous than those of the genitalia. As a result, this updated key was loosely informed by the iteration provided by Coscarόn’s (1983a), although her habitus plates will still greatly aide in identification.

The species of Rasahus fall into two distinctive groups. This is strongly suggested by two corresponding sets of characters: Group 1, the sulcicollis group, has the pale macula of the hemelytral apex absent or not contained by medial cell and males with expanded to deeply lobate parameres, whereas Group 2, the hamatus group, has the round pale macula well-contained in medial cell of the hemelytral membrane and males with slender, clavate parameres. Monophyly of these groups was supported by Morrone & Coscarόn’s (1998) cladistic analysis (although F. vittata was not included). This division occurs at couplet 5 in the key below, although all species in couplets 1–4 belong to the sulcicollis group. Of the new species erected herein, R. deliquus sp. nov. and R. abolitus sp. nov. undoubtedly belong to the sulcicollis group. Although only the female is known, it seems very likely that R. nesiotes sp. nov. belongs to the hamatus group.

It should be noted that the coloration of the connexiva requires additional study regarding its diagnostic use. In some species, notably R. biguttatus and R. hamatus , this color pattern is sexually dimorphic, with males having predominantly yellow connexiva and females having distinctly bicolorous (yellow-black) connexiva (Swanson, pers. obs.). In cases where connexival color is used in the key, consulting other characters in the current and subsequent couplets should relieve difficulty in segregating pairs or clusters of species.

The monotypic genus Froeschnerisca Coscarόn, 1996 strongly resembles species in Rasahus , with the single species being originally erected within that genus by Coscarόn (1983a). Diagnostic characters of Froeschnerisca include a “very accuminated” scutellum (vs. not accuminated in Rasahus ), a subrectangular pygophore (vs. quadrangular to rounded in Rasahus ), a complex basal plate of the male genitalia (vs. simple in Rasahus ), and female tenth tergites with a projection (vs. without a projection in Rasahus ) (Coscarόn 1990, 1995). This generic diagnosis might easily be based on characters that are either autapomorphic (basal plate, tenth tergite) and/or variable (scutellum, shape of pygophore) within the context of Rasahus , and like the general case of R. myrmecinus stat. rev. et comb. nov., the taxon easily fits within the diagnosis of Rasahus , despite slight morphological variability. Thus, the genus should probably be subsumed into Rasahus . As I lack any examined material of this species or the means to test this in a phylogenetic context, I have refrained from doing so at this time. However, the single species is included in the key to Rasahus to facilitate identification of this clearly closely-related taxon.

Figures

FIGURE 5. Male external genitalia: (A–C) Rasahus deliquus sp. nov.: (A) median process of pygophore; (B) left paramere; (C) right paramere; (D–F) R. abolitus sp. nov.: (D) median process of pygophore; (E) left paramere; (F) right paramere; (G–I) R. myrmecinus stat. rev. et comb. nov.: (G) median process of pygophore; (H) left paramere; (I) right paramere.

FIGURE 8. Holotype of Pirates myrmecinus housed in ZMHB: (A) lateral habitus, left side; (B) dorsal habitus; (C) ventral habitus; (D) head, pronotum, and forelegs, left lateral view; (E) thoracic pleura, right lateral view; (F) labels. Photographed by Jürgen Deckert (ZMHB); used with permission.

FIGURE 9. Belizean specimens of Rasahus myrmecinus stat. rev. et comb. nov.: (A–C) adult male: (A) dorsal habitus; (B) caudal view of terminalia; (C) lateral habitus; (D–F) adult female: (D) dorsal habitus; (E) caudal view of terminalia; (F) lateral habitus.

FIGURE 10. Protibial fossula spongiosa, lateral view: (A) Belizean male of Rasahus myrmecinus stat. rev. et comb. nov.; and (B) R. abolitus sp. nov. (holotype).

FIGURE 11. Metapleural sulcus, lateral view: (A) Belizean specimen of Rasahus myrmecinus stat. rev. et comb. nov., adult male; (B) idem., adult female; (C) R. abolitus sp. nov. (holotype); (D) R. albomaculatus; (E) R. biguttatus; (F) R. setosus; (G) R. sulcicollis; (H) Melanolestes picipes; and (I) Sirthenea stria carinata. Solid lines separate genera, dashed lines separate species.