Zelus nugax Stal , 1862

Zhang, Guanyang, Hart, Elwood R & Weirauch, Christiane, 2016, A taxonomic monograph of the assassin bug genus Zelus Fabricius (Hemiptera: Reduviidae): 71 species based on 10,000 specimens, Biodiversity Data Journal 4, pp. 8150-8150 : 8150

Zelus nugax Stal, 1862

Zelus nugax Stål, 1862, p. 450-451, orig. descr. (subgenus Diplodus ); Stål, 1872, p. 91, cat. (subgenus Diplodus ); Lethierry and Severin, 1896, p. 152, cat.; Champion, 1898, p. 257, 2, note and list; Kuhlgatz, 1902,, p. 266, note; Fracker, 1913, p. 239, 240, key and list (subgenus Diplodus ); Fracker and Bruner, 1924, p. 171, list; Haviland, 1931, p. 137, 152, list and note; Leonard and Mills, 1931, p. 309-323, note; Wygodzinsky, 1947, p. 431, note; Wygodzinsky, 1949a, p. 49, checklist; Guagliumi, 1953, p. 16, note; Wygodzinsky, 1957, p. 268, junior syn. of Zelus obscuridorsis ; Sucre, et. al., 1966, p. 31, note; Hart, 1986, p. 540, redescription, note, fig., key and lectotype desig.; Maldonado, 1990, p. 330, cat.

Diplodus nugax : Walker, 1873, p. 124, cat; Uhler, 1886, p. 24, checklist; Hart, 1986, p. 540, lectotype desig.

Zelus rufigeniculatus Haviland, 1931, p. 137, 148, 153-154, list, fig. and orig. descr. (subgenus Diplodus ); Wygodzinsky, 1949a, p. 50, checklist; Hart, 1986, p. 540, junior syn. of Z. nugax .

Materials

Type status: Lectotype. Occurrence: catalogNumber: UCR_ENT 00041008 ; occurrenceRemarks: Lectotype of Zelusnugax Stål, 1862, designated by Hart (1986). Verbatim label info: Mexico / Salle / nugax Stal / Lectotype Zelusnugax Stal / designated by E.R.Hart / Typus / NHRS-GULI 000000336; recordedBy: Salle; sex: Adult Female; otherCatalogNumbers: NHRS-GULI 000000336; Taxon: scientificName: Zelusnugax; family: Reduviidae; genus: Zelus; scientificNameAuthorship: Stål, 1862; Location: country: MEXICO; locality: unknown ; Identification: identifiedBy: G. Zhang; dateIdentified: 2012; Event: eventDate: No date provided; Record Level: institutionCode: NHRS Type status: Other material. Occurrence: occurrenceRemarks: Lectotype of Zelusrufigeniculatus Haviland, 1931, designated by Hart (1986). Bears following labels: Type / Berbice Brit. Guiana-October 1922-e. coll. M. D. Haviland-d.d. Collegium Newnhamense / Pres. By Mrs. Brindley-B.M. 1928-172 / Zelusrufigeniculatus Haviland; recordedBy: Haviland, M.D.; sex: Adult Female; Taxon: scientificName: Zelusnugax; family: Reduviidae; genus: Zelus; scientificNameAuthorship: Stål, 1862; Location: country: Guyana; locality: Berbice ; Event: eventDate: 1922-10; Record Level: institutionCode: BMNH Type status: Other material. Occurrence: occurrenceRemarks: Paralectotype of Zelusrufigeniculatus Haviland, 1931, designated by Hart (1986). Bears following labels: Type / Berbice Brit. Guiana-October 1922-e. coll. M. D. Haviland-d.d. Collegium Newnhamense / Pres. By Mrs. Brindley-B.M. 1928-172 / Zelusrufigeniculatus Haviland; recordedBy: Haviland, M.D.; sex: Adult Female; Taxon: scientificName: Zelusnugax; family: Reduviidae; genus: Zelus; scientificNameAuthorship: Stål, 1862; Location: country: Guyana; locality: Berbice ; Event: eventDate: 1922-10; Record Level: institutionCode: BMNH

Description

Figs 147, 148, 149

Male: (Fig. 147a, b) Small, total length 9.54-10.78 mm (mean 10.23 mm, Suppl. material 2); slender. COLORATION: Dorsal surface brown, sometimes disc of posterior pronotal lobe and scutellum yellowish-brown. Lateral and ventral surfaces generally yellowish-brown. Femora with at least apices and often entire enlarged apical area dark reddish-brown,tibiae with variable dark reddish-brown bands. VESTITURE: Sparsely setose. Head with moderate to long erect setae and recumbent setae. Anterior pronotal lobe with short, recumbent setae dorsally confined to setal tracts, laterally with longer, recumbent to erect setae; posterior pronotal lobe with recumbent setae. Abdomen with short, recumbent and short to moderately long, erect setae. STRUCTURE: Head: Elongated, L/W = 2.48. Postocular lobe long; in dorsal view anteriorly gradually narrowing, posterior portion constant, slightly narrower. Eye smallish; lateral margin only slightly wider than postocular lobe; dorsal and ventral margins removed from surfaces of head. Labium: I: II: III = 1: 2.0: 0.4. Basiflagellomere diameter larger than that of pedicel. Thorax: Anterolateral angle with inconspicuous subtuberculate projection; medial longitudinal sulcus shallow near collar, deepening posteriorly. Posterior pronotal lobe with rugulose surface; disc distinctly elevated above humeral angle; humeral angle armed, with dentate projection. Scutellum long; apex slightly pointed dorsally. Legs: Very slender, femoral diameters subequal. Hemelytron: Slightly surpassing apex of abdomen, not more than length of abdominal segment seven; quadrate cell small; Cu and M of cubital cell subparallel, slightly converging. GENITALIA: (Fig. 148) Pygophore: Ovoid; not expanded laterally in dorsal view. Medial process cylindrical; very slender; long, only slightly shorter than paramere; laterally compressed; semi-erect; nearly straight; apex in posterior view acute, without modification. Paramere: Cylindrical; moderately long, achieving apex of medial process; directed posteriad; nearly straight; apical part not enlarged, apex somewhat truncate. Phallus: Dorsal phallothecal sclerite shield-shaped; apical portion of phallothecal sclerite distinctly tapered, slightly convex, laterally rounded, not forming angle; posterior margin of foramen deeply concave. Struts attached to dorsal phallothecal sclerite; massively fused. Basal plate arm moderately robust; widely separate; diverging; in lateral view very slightly curved; bridge moderately long; extension of basal plate not distinctly visible.

Female: (Fig. 147c, d) Similar to male, except for the following. Larger than male, total length 12.25-14.14 mm (mean 12.99 mm, Suppl. material 2).

Diagnosis

The slender, cylindrical paramere and the laterally compressed medial process can separate males of this species from most other species of the genus. Difficult to distinguish from Z. pedestris , but the paramere apex is generally more truncate, the dorsal phallothecal sclerite usually without lateral indentation, and the basal plate arms are separate in most specimens (see taxon discussion).

Distribution

Mexico, Central America and South America (Fig. 149). Countries with records: Argentina, Belize, Brazil, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Peru, Suriname, Trinidad and Tobago, USA, and Venezuela.

Taxon discussion

This is by far the most widespread species of the Zelus nugax species group, and one of the most widespread members of the genus. In Ecuador, Mexico and Central America, Z. nugax is apparently among the most common species of reduviids, occurring in second growth foliage and tall grasses throughout its range. Other than a variation in color from yellowish-brown to dark brown in any given area and a more noticeably produced scutellar apex in South America, there are little readily apparent external variations in the species. In the internal male genitalia, however, we find some noticeable geographic variations. In South America the basal plate arms are apparently always separate, while there seems to be tendency toward fusion of these arms as one progresses northward to Mexico.

The following discussion on some of the diagnostic characters may be useful for separating species when confusions arise, but as we have not clearly defined the boundaries between Z. nugax and Z. pedestris , reliable identification may not be achieved at all times. We will discuss this in the next paragraph. The straight bladelike medial process of Z. nugax distinguishes it from Z. impar and Z. illotus , both of which have similar appearances to Z. nugax , but both have recurved medial processes. The less rounded pygophore and more blunted paramere separate this species externally from most male specimens of Z. pedestris . Although it is difficult to separate the females of Z. nugax from Z. illotus and Z. pedestris , there appears to be some differences among these species. The normal lack of erect setae on the dorsal surface of the posterior pronotal lobe of Z. illotus and lower posterior margin of the anterior pronotal lobe of Z. pedestris usually serve as diagnostic characters for someone with large series and a familiarization with all three species.

It remains unresolved if Z. nugax and Z. pedestris are distinct species. They are currently delimited based on several characters of the male genitalia, which, however, do not appear to be fixed. With regards to four characters (paramere apex shape, fusion of basal plate arms, lateral indentation on dorsal phallothecal sclerite, and basal plate arm extension) used in delimitation, the following combinations have been observed: (1) paramere apex acute, basal plate arms fused, phallothecal indentation present and basal plate arm extension present and expanded laterally (observations based on specimens from Santa Catarina, Brazil); (2) paramere apex truncate, slightly enlarged, somewhat diamond-shaped, basal plate arms fused, indentation absent and extension present, laterally expanded (La Molina, Peru); and (3) paramere apex truncate, slightly enlarged, basal plate arms separate, phallothecal indentation absent and extension absent or inconspicuous (El Valle, Panama). Following the phylogenetic species concept sensu Wheeler and Platnick ( Wheeler and Platnick 2000), we would call each population a different species. We restrained from doing this as we have not thoroughly examined the ranges of variations.

Both the types of Z. nugax and Z. pedestris are females, further complicating the application of the names as we have not been able to distinguish females of the two species. The type of Z. nugax is from Mexico and that of Z. pedestris from South America (country not recorded). Zelus nugax and Z. pedestris overlap broadly in northern South America, but Z. nugax appears to be absent South of Peru and in most of Brazil and Z. pedestris not recorded from North and Central Americas. This geographic pattern currently serves as an additional means to apply the names.