Zelus Fabricius, 1803

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 Fabricius, 1803

Zelus Fabricius, 1803, p. 281, orig. descr.; Latreille, 1804, p. 260, list; Latreille, 1807, p. 129, list; Latreille, 1810, p. 433, type desig.; Lepeletier and Serville, 1825, p.815, list and descr.; Laporte, 1832, p. 9, type desig.; Burmeister, 1835, p. 225, descr.; Brulle, 1836, p. 316-317, descr.; Blanchard, 1840, p. 100, descr. and note; Blanchard, 1845, p. 433, 438, list and note; Herrich-Schaeffer, 1848, p. 88, descr. and note; Kolenati, 1857, p. 458-459, descr.; Stål, 1861, p. 148, descr.; Stål, 1862, p. 449-454, key and subgeneric descr. (with subgenus Zelus ); Carpenter and Westwood, 1863, p. 565, note; Mayr, 1866, p. 138, list; Stål, 1866, p. 296, list; Stål, 1868, p. 107, restriction of definition; Stål, 1872, p. 69, 88, key and cat. (with subgenus Zelus ); Walker, 1873, VII., p. 49, key, VIII., p. 131-136, cat.; Berg, 1879, p. 150, list (with subgenus Zelus ); Uhler, 1886, p. 24, checklist; Provancher,1887, p. 179, note; Lethierry and Severin, 1896, p. 151, cat.; Champion, 1898, p. 251, cat. and note; Kirkaldy, 1900a, p. 263, type verification; Kirkaldy, 1900b, p. 242, syn.; Kirkaldy, 1902, p. 149, note; Fracker, 1913, p. 223, 238-240, key and note (with subgenus Zelus ); Van Duzee, 1916, p. 30, checklist (with subgenus Zelus ); Van Duzee, 1917, p. 258-259, cat. (with subgenus Zelus ); Blatchley, 1926, p. 567-568, key, descr. and note (with subgenus Zelus ); Readio, 1927, p. 167, 168-169, key, descr. and note; Zimmerman, 1948, p. 137, note; Wygodzinsky, 1949a, p. 48, checklist; Fracker and Usinger, 1949, p. 277, key to nymphs; Alayo, 1967, p. 5, 35, list, key and note; Hart, 1986, key to North American species; Hart, 1987, key to Caribbean species; Maldonado, 1990, p. 325-332, cat.

Reduvius Fabricius, 1775 (type by subsequent desig., Cimex personatus Linnaeus, 1758), Lepeletier and Serville, 1825 (in part), p. 272, descr.; Perty, 1834 (in part), p. 173, list of species.

Arilus Hahn, 1831 (type by subsequent designation, Cimex carinatus Forster, 1771); Burmeister, 1835 (in part), p. 227-228, descr.; Herrich-Schaeffer, 1848 (in part), p. 33-35, descr.

Euagoras Burmeister, 1835 (type by subsequent designation, E. stollii Burmeister, 1835) (in part), p. 226, descr.; Amyot and Serville, 1843 (in part), p. 368, descr. (as Evagoras ); Herrich-Schaeffer, 1848 (in part), p. 43-44, descr.; Stål, 1855 (in part), p. 189, list (as Eccagoras ); Stål, 1861, p. 148, (in part) junior syn. of Zelus Fabr.; Mayr, 1866, p. 139, list; Walker, 1873, p. 49, 117, key and cat.; Provancher, 1887, p. 182, descr. (as Evagoras ); Kirkaldy, 1900b, p. 242, junior syn. of Zelus Fabr.; Kirkaldy, 1903, p. 215-216, note.

Diplodus Amyot and Serville, 1843, p. 370, descr.; Burmeister, 1853, p. 91, list (included in Euagoras Burm.); Stål, 1860, p. 74, list; Stål, 1862, p. 450, descr. (as subgenus of Zelus ); Stål, 1866, p. 296, key; Stål, 1872, p. 90, list (as subgenus of Zelus ); Walker, 1873, VII., p. 49, VIII., p. 123, key and cat. (as Diploda ); Berg, 1879, p. 151, list (as subgenus of Zelus ); Uhler, 1886, p. 24, checklist; Provancher, 1887, p. 179, key and descr.; Kirkaldy, 1903, p. 232, note; Fracker, 1913, p. 239, 240, key and list (as subgenus of Zelus ).

Darbanus Amyot and Serville, 1843 (type by monotypy, D. nigrolineatus ); Provancher, 1872, p. 106, species descr.; Uhler, 1886, p. 24, checklist; Provancher, 1887, p. 179, 181, key and note; Van Duzee, 1912, p. 324; Fracker, 1913, p. 241, note.

Pindus Stål, 1862, p. 454, orig. descr. (as subgenus of Zelus ); Stål, 1866, p. 296, key (as genus); Stål, 1872, p. 92, list and cat., as subgenus of Zelus ); Walker, 1873, VII., p. 66, list and cat. (as genus); Berg, 1879, p. 150, list (as subgenus of Zelus ); Thierry and Severin, 1896, p. 151, cat.; Fracker, 1913, p. 223, 240, key and list; Van Duzee, 1916, p. 30, checklist; Van Duzee, 1917, p. 261, cat.; Blatchley, 1926, p. 569, key.

Diplacodus Kirkaldy, 1900b, p. 242, new name for Diplodus A. and S. (preocc.).

Diplocodus Van Duzee, 1916, p. 30, checklist (new name for Diplacodus Kirkaldy, preocc.); Van Duzee, 1917, p. 260, cat.; Blatchley, 1926, p. 569, key.

Iquitozelus Bérenger, 2003, p. 23, orig. descr., syn. nov. (current study).

Zelus Cimex longipes Linnaeus, 1767

Description

Male: Small to large, total length 8-25 mm (Suppl. material 2), with most of moderate sizes (11-18 mm); usually slender (length/width = 4.0-5.0), some species relatively robust (<3.5) to rather slender (>6.0). COLORATION: Colors and patterns of preserved specimens variably yellowish-brown, reddish-brown, orange-brown, and brownish-black to black, with most species uniformly colored. VESTITURE: Most species with moderately dense or dense, fine, short, recumbent and short, long, erect setae; some species with short, spine-like setae on head and pronotum; few species nearly glabrous. Setation on legs sparse in most species; profemur and tibia with dense sundew setae in some species. STRUCTURE: Head: Length much greater than width across eye. Postocular lobe usually longer than anteocular, tube-like posteriorly in most species. Ocellus raised, directed somewhat laterally. Eye variably sized, not protruding above or below dorsal or ventral surfaces of head, with one exception ( Zelus grandoculus sp. n.). Antenna: Scape and basiflagellomere long and subequal in length, usually longer than head and pronotum combined; pedicel and distiflagellomere short and about 1/3 length of scape. Scape thickest; basiflagellomere usually thicker than pedicel, subequal in some species. Labium: Segment II longest, 1.3-2.2x length of segment I; segment III shortest, usually 0.5x length of segment I; variably curved between segments I and II. Thorax: Anterior pronotal lobe about 1/2 to 3/4 length of posterior lobe; anterolateral angles of pronotal collar rounded, with or without tuberculate protrusion; medial dorsal longitudinal sulcus usually shallow at collar, deepening through posterior 1/2; sometimes with subtuberculate elevation near posterior margin laterad to medial sulcus. Posterior pronotal lobe rugulose (not conspicuous in species with dense setation); slightly or greatly wider than anterior lobe; disc of most species elevated above humeral angle and posterior margin of lobe; humeral angle with tuberculate to long spinous lateral process, rounded and unarmed in small number of species. Scutellum in most species with angulate apex, slightly produced and projected upward in some species. Legs: long, slender in most species; femoral diameters generally subequal; pro- and metafemoral lengths subequal, greater than mesofemoral length. Hemelytron: Attaining or surpassing apex of abdomen, by large proportion in some species. Quadrate cell small to large; median vein conspicuous in some species and not visible in many. Cu and M of cubital cell subparallel in most species, converging in some. Abdomen: Lateral margins subparallel; ventral outline usually straight, in some species somewhat concave and abdomen appearing arched (see "Material and methods" for discussion of this character). Genitalia: Segment eight usually short, less than 1/2 length of pygophore; posterior margin generally slightly concave, straight in some species, never convex. Pygophore: ovoid to elongated; slightly to greatly expanded laterally close to base of paramere; dorsal bridge short to long. Medial process single, not bifurcating, of variable length and shape; triangular or cylindrical as most common configuration; apex blunt or with hooklike process. Paramere generally cylindrical, often swollen and bending apically, length variable. Phallus: Dorsal phallothecal sclerite generally semi-cylindrical, broad and shield-like in many species, elongated in some; dorsal surface lacking armature in most species, with projection, process or elevation in some species; lateral margins usually straight or convex, constricted or recurved in some species; apical part keeled in middle and/or curved dorsad; apex usually rounded or truncate, with or without medial emargination. Struts attached to dorsal phallothecal sclerite in majority of species; apical part recurved dorsad and often semi-circular; bridge connecting two sides in many species. Basal plate arm slender to heavy, separate or fused; basal plate bridge present, variable in width and degree of sclerotization; basal plate extension short, often extended onto basal plate arm.

Female: Larger than male. Coloration usually similar to that of male and more variable in some species, but may differ between sexes dramatically in certain species. Eye and ocellus smaller than in male in some species. Basiflagellomere not swollen and about equal diameter as or smaller than pedicel. Lateral process on humeral angle, if present, usually more produced and longer than in male. Mesofemur slightly swollen in many species. Lateral margins of abdomen expanded in some species.

Diagnosis

This genus is distinguished from other genera of the New World Harpactorini by the cylindrical head, the length of the head being at least 1.9X its width; the unarmed antenniferous tubercles; the second labial segment being at least 1.3x the length of the first segment; the long scape and basiflagellomere that are subequal in length and the short pedicel and distiflagellomere; the generally unarmed (i.e. no tubercles or spines) disc of the posterior pronotal lobe (except in Zelus tetracanthus Stål, 1862, Zelus lewisi sp. n. and Zelus minutus Hart, 1987); the humeral angle with or without process, and if present, usually not prominently projected; the legs with sundew setae and sticky glands ( Zhang and Weirauch 2013); the profemur subequal in length and diameter to the metafemur; and the medial process of pygophore single, not bifurcating. Zelus is apparently closely related to three other genera, Atopozelus Elkins, Ischnoclopius Stål and "Hartzelus" [manuscript name], that share many of the aforementioned characters. It is separated from Atopozelus by the presence of paramere (lacking in Atopozelus ). Ischnoclopius is distinguished from Zelus by its rather slender body form (length:width ratio greater than seven), the very long profemur, at least 0.6x of body length, and the very short paramere. An undescribed genus, "Hartzelus" (Gil-Santana and Berenger, pers. comm.), which would be in part based on species removed by us from Zelus , differs from Zelus in having a bifurcating medial process of the pygophore (single in Zelus ) and generally more slender legs. No Old World species of Harpactorini are similar or appear to be closely related to Zelus . Confusion may potentially arise with members of genera that show a similar slender body form and slender legs (e.g., Euagoras and Vestula Stål), but these are distinguished from Zelus based on the characters listed above.

Distribution

Native to (except for Chile) and throughout the New World, including the Caribbean, with highest diversity in the Neotropics. One species ( Z. renardii ) has been introduced to Hawaii, the Polynesian islands, Jamaica, Philippines, Spain, Greece and Chile.

Biology

We provide a non-exhaustive account of the biology of various species of this genus. As with other harpactorines, species of Zelus generally do not show associations with or preferences of host plants, probably due to their generalist habits. However, two recent studies have found two species of Zelus that have both nymphs and adults occurring in the same plant species in relatively large quantities. In Gil-Santana and Alves (2011), based on a multi-year study the authors observed forty-seven females, twenty-seven males and fifteen nymphs of Z. versicolor from Bidens rubifolia Kunth ( Asterales , Asteraceae ) in a single site in the city of Nova Friburgo, Brazil. Interestingly, they did not see individuals of the same species in other plants in the same site, which can be seen as evidence for host plant preference. In French Guiana Revel et al. (2010) counted as many as 405 individuals of Zelus annulosus ( Stål, 1866) and its egg masses from several pubescent plant species, including (but not limited to) Hirtella physophora Mart. & Zucc. ( Chrysobalanaceae ), Cordia nodosa Lam. ( Boraginaceae ) and Tococa guianensis Aubl. ( Melastomataceae ); all three are myrmecophytes. They hypothesized an intriguing tri-party mutualistic relationship between the assassin bug, an ant ( Allomerus decemarticulatus Mayr) and the plants.

Several species of Zelus are possibly mimics of various other insects. Zelus errans Fabricius, 1803, Zelus vespiformis Hart, 1987 and to some extent Zelus vagans Fabricius, 1803 and Zelus gracilipes sp. n. have wing and body color patterns similar to many braconid wasps, an intriguing form of mimicry seen also in a number of other Neotropical harpactorine genera. Zelus vagans shows areas of black and orange colors, however, the posterior pronotal lobe is medially dark and laterally orange. Zelus gracilipes also shows a uniformly orange posterior pronotal lobe, but the hemelytron is uniformly dark and lacks the banding pattern typical to a wasp mimic. Zelus nigromaculatus Champion, 1899 has an appearance similar to that of a typical vespid, the only species in this genus with that kind of color pattern. Zelus laticornis (Herrich-Schaeffer, 1853), Zelus grassans Stål, 1862 and Zelus ruficeps Stål, 1862 have red and dark markings on abdomens and orange or reddish dorsal surfaces, a pattern found in many species of pyrrhocorids (e.g., Dysdercus spp.) and coreids (e.g. Hypselonotus spp.). Interestingly, in Z. laticornis , it is only the females showing this coloration. Certain color forms of Z. longipes are possibly mimics of the milkweed bug, Oncopeltus fasciatus (Dallas).

Weirauch et al. (2012) studied predatory and mating behaviors of Z. renardii and Z. tetracanthus and discussed a possible link between biological attributes and invasion potential. Law and Sediqi (2010) experimentally demonstrated that sticky substance derived from egg mass coating improves predation success and substrate adhesion ability of Z. renardii first instar.

Taxon discussion

The generic limit of Zelus is now relatively well defined and the genus can be separated from all other but one genera of New World Harpactorini based on characters discussed in the diagnosis. Based on a molecular phylogeny, Zhang and Weirauch (2014) recovered the monophyly of Zelus , Atopozelus and "Hartzelus" (which includes Z. araneiformis , a species we remove from Zelus ). In that analysis, Ischnoclopius was represented by a single species and placed as sister to Atopozelus . The genera Atopozelus , "Hartzelus", Ischnoclopius and Zelus together constitute a monophyletic group in the same study, and we here refer to this group the " Zelus clade". Without a cladistic analysis, questions remain if the characters used to diagnose Zelus are synapomorphies of that genus. It is almost certain that the unbifurcating medial process represents a symplesiomorphic state as that character can be seen in Atopozelus , Ischnoclopius and many other Neotropical harpactorines. The unarmed antenniferous tubercles are also plesiomorphic to Zelus , since all other genera of the Zelus clade exhibit that condition, but may be synapomorphic to the Zelus clade. We agree with Forero (2012) that Zelus is defined mainly by the absence of apomorphies seen in other genera. Future research should illuminate this issue by studying the distribution and the polarity of characters with a formal cladistic framework.

The genus that we are uncertain about its relationship with Zelus is Pronozelus Forero, erected by Forero (2012) to accommodate a new species, Pronozelus schuhi Forero, 2012. This species appears to possess all the characters diagnostic of Zelus , but also shows some peculiar characters. The principal characters separating Pronozelus from Zelus include the laterally expanded posterior pronotal lobe, the prominent, greatly expanded posterolateral rim of pygophore lateral to paramere socket, and the posterior pronotal lobe greater than 2.2x length of the anterior lobe. The conspicuous lateral expansion of the posterior pronotal lobe is not observed in any species of Zelus , but this character appears to be autapomorphic in the Zelus clade and does not support P. schuhi being phylogenetically separated from Zelus . We have not done an extensive survey of the condition of the posterolateral rim of the pygophore and cannot determine the distribution or polarity of the lateral prominence as exhibited in P. schuhi . In Zelus rosulentus sp. n., the posterolateral part of the pygophore also appears to be expanded, although not as prominent as that seen in P. schuhi . Finally, according to measurements done in this study, in Zelus spp. the posterior pronotal lobe frequently exceeds 2.2x length of the anterior lobe, thereby negating the use of that character as a basis for placing P. schuhi outside Zelus . Despite the foregoing discussion, we have opted to not transfer P. schuhi to Zelus or synonymize Pronozelus with Zelus . The polarity of the characters diagnostic to either genus has not been clearly defined. There remains a possibility, although we think a small one, that P. schuhi represents a lineage sister to Zelus .

Bérenger (2003) 's new species, Iquitozelus couturieri , exhibits all the characters diagnostic of Zelus , except for those of the male genitalia as the known specimens are all females. The main character that Bérenger used as the basis for erecting a new genus, i.e., the "foliaceous expansion of the VI connexivum segment", appears to be autapomorphic within the Zelus clade. Synonymy of Iquitozelus with Zelus is warranted and established here. We further postulate that I. couturieri is most closely related to Zelus amblycephalus sp. n., Zelus umbraculus sp. n. or Zelus umbraculoides sp. n. Further discussions regarding the status of Iquitozelus and the specific membership of Zelus couturieri syn. nov. ( Bérenger, 2003) are presented in the treatment of that species.

Maldonado (1990) considered two unpublished, manuscript names invalid, and they are " Diplodus armiger" and " Diplodus melanophthalmus". They appeared in Dohrn (1860). We follow this treatment.

Except for several pairs or complexes of closely related species, identification of males can be almost always unambiguously performed based on exposed genitalic structures such as paramere and medial process, further corroborated with phallic structures, external morphology and coloration. Identification of females of many species, where females appear to be as distinct as males, is straightforward based on coloration and external morphology. However, identification can be difficult for closely related species, where females are indistinguishable based on external morphology. In these cases, association of males and females and identification of females were primarily based on collecting event information. Sexual dimorphism presents another special challenge. While most species show limited sexual dimorphism that does not go beyond minor size and coloration differences, some species exhibit pronounced differences between the sexes (see Material and Methods for discussion of association of male and female specimens). Based on the observation that species in closely related genera do not exhibit strong sexual dimorphism, we here hypothesize that pronounced sexual dimorphism is a derived condition within Zelus .

Species groups

We find here that previous subgeneric groups are based on superficial resemblance and these are not adopted. Instead, we recognize eleven species groups in the current study, based primarily on characters of the male genitalia, but also on non-genitalic external morphology if those characters can be applied to both sexes. Several species for which only females are known are therefore not assigned to a species group. Although the groupings proposed here are not based on a cladistic analysis, they show a degree of congruence with the relationships recovered in the phylogenetic analysis based on molecular data in Zhang and Weirauch (2014) and many of the characters are putative synapomorphies of the groups. A brief discussion of the species groups is presented below.

1. Zelus tetracanthus species group.

Zelus minutus Hart, 1987, Zelus prolixus Stål, 1860, Zelus rosulentus sp. n. and Zelus tetracanthus Stål, 1862.

Members of this group have a rather broad, indistinct medial process, the base of which is nearly continuous with or inseparable from the ventral rim of the pygophore. We speculate that this character represents a plesiomorphic condition as it is seen in several other genera of the New World Harpactorini and thus the condition of the medial process does not necessarily support the monophyly of this group. Zelus tetracanthus and Z. minutus also both have tubercles on the disc of the posterior pronotal lobe, which are more pronounced in the former. Comparative views of male genitalia are shown in Fig. 2.

2. Zelus luridus species group.

Zelus ambulans Stål, 1862, Zelus antiguensis sp. n., Zelus exsanguis Stål, 1862, Zelus grandoculus sp. n., Zelus luridus Stål, 1862 and Zelus spatulosus sp. n.

This is a group of species with primarily a North American distribution, with some species extending to northern Central America. The males show an apically expanded paramere and a triangular medial process that has a protrusion at the base but lacks any apical modifications. Notably, Z. spatulosus has a slender medial process, deviating greatly from the remainders of the group. It is placed in this group mainly because of the apically expanded paramere and the uniform coloration. Zelus ambulans and Z. exsanguis have the humeral angle elevated to about same level of and nearly continuous with the disc of the posterior pronotal lobe, a condition rarely seen in the genus. The coloration is quite homogenous among members of this genus, most of which have a uniform greenish (in live specimens) or dull brownish (in preserved specimens) habitus, with only Z. ambulans showing variable patterns or banding on the pronotum or legs. Comparative views of male genitalia are shown in Fig. 3.

3. Zelus mimus species group

Zelus inconstans Champion, 1898 and Zelus mimus Stål 1862.

Members of this group, consisting of only two species, exhibit a highly unique paramere and a medial process of the pygophore. The paramere is slender and apically curved dorsad at an angle of nearly ninety degrees. The medial process, as is especially evident in Z. inconstans , possesses a simple posterior liplike fold at the apex; its lateral margins are subparallel and not broadened significantly at the base. Both have a semi-cylindrical dorsal phallothecal sclerite which is modified by a fold running obliquely toward the base from the middle of the lateral margins. Both species, being quite small, exhibit the usual reduction of setal tracts common to nearly all small species. Comparative views of male genitalia are shown in Fig. 4.

4. Zelus nugax species group.

Zelus grassans Stål, 1862, Zelus illotus Berg, 1879, Zelus impar Kuhlgatz, 1902, Zelus nugax Stål, 1862 and Zelus pedestris Fabricius, 1803.

This is a group of smallish species with quite variable distributional ranges. The defining characters include a slender, laterally compressed medial process that is curved or recurved, and an acute apex of the dorsal phallothecal sclerite (except in Z. grassans ). Zelus nugax has one of the widest distribution ranges in this genus, ranging from much of Mexico to northern South America. Zelus grassans is found primarily in Central America and the remaining two species mainly in northern South America. Comparative views of male genitalia are shown in Fig. 5.

5. Zelus puertoricensis species group.

Zelus bruneri De Zayas, 1960, Zelus puertoricensis Hart, 1987, Zelus subimpressus Stål, 1872 and Zelus zayasi Bruner and Barber, 1937.

Members of this group are restricted to the Caribbean. They can be easily recognized by the rather slender body form. The posteriorly directed, robust medial process with a somewhat blunt apical protrusion is also distinctive of this group. The basal plate arms are widely separate and diverging and these features are rare in other species in the genus. They show resemblance to species of the Zelus renardii species group, especially to Z. cervicalis . Zelus bruneri was not physically examined, but the rather slender body form as seen in the original illustration places it within this group. Comparative views of male genitalia are shown in Fig. 6.

6. Zelus renardii species group.

Zelus cervicalis Stål, 1872 and Zelus renardii Kolenati, 1856.

The two members of this group are very likely sister species since they share a number of unique characters: the apex of the medial process is greatly bent ventrad and hooklike, the lateral margin of the dorsal phallothecal sclerite is recurved dorsad and the basal part of the strut is absent. Both species are mainly distributed in North and Central America, but Z. cervicalis extends to northern South America. Comparative views of male genitalia are shown in Fig. 7.

7. Zelus armillatus species group.

Zelus amblycephalus sp. n., Zelus annulosus ( Stål, 1866), Zelus armillatus (Lepeletier & Serville, 1825), Zelus conjungens ( Stål, 1860), Zelus janus Stål, 1862, Zelus leucogrammus (Perty, 1833), Zelus lewisi sp. n., Zelus litigiosus Stål, 1862, Zelus ruficeps Stål, 1862, Zelus sulcicollis Champion, 1899, Zelus umbraculoides sp. n. and Zelus umbraculus sp. n.

This is one of the two largest groups in the genus (the other being the Zelus panamensis species group). Species in this group are generally robust and large-sized (15-25 mm), and some are among the largest in the genus. The most distinctive character is that of the medial process, which has the apex slightly projected into two minute small lateral prongs or processes. This condition is different from that in several species groups listed below, where the apex of the medial process is hook-like and more strongly projected. The lateral spine of the humeral angle tends to be pronounced and somewhat broadened into a dentate effect. The pygophore is large, rounded, and somewhat shortened relative to the total length of the individual. The dorsal phallothecal sclerite having dorsolateral expansions or projections close to the basal arm is also unique to some species of this group. This condition, however, is not seen in Z. amblycephalus , Z. umbraculus , or Z. umbraculoides , which appear to be divergent from the remainders of the group, but the features of the medial process unambiguously place them in this species group. Comparative views of male genitalia are shown in Figs 8, 9.

8. Zelus longipes species group.

Zelus bahiaensis sp. n., Zelus errans Fabricius, 1803, Zelus longipes (Linnaeus, 1767), 1803 and Zelus vespiformis Hart, 1987.

This and the next species group ( Zelus vagans species group) possess dense, spine-like setae on the head and pronotum, and a rounded, unarmed humeral angle, both characters rather unique in Zelus and probably synapomorphies uniting the two groups. The former character is possibly homoplastic as it is also seen in two species in the Zelus armillatus species group. The medial process is slender and cylindrical and this condition is among the most extreme in the genus. It is semi-erect and posteriorly directed. The paramere exceeds the apex of the medial process. The dorsal phallothecal sclerite has subparallel margins and lacks obvious modifications or ornamentations (except for small lateral folds in Z. longipes ). Some individuals of Z. errans and Z. vespiformis appear to be wasp mimics. Comparative views of male genitalia are shown in Fig. 10.

9. Zelus vagans species group.

Zelus aithaleos , Zelus championi sp. n., Zelus fuliginatus sp. n., Zelus gracilipes sp. n. and Zelus vagans Fabricius, 1803.

Species of the Zelus vagans group share two characters also present in the preceding group ( Zelus longipes species group): spinelike setae and rounded humeral angle. However, they differ in the structure of the male genitalia in significant ways. The medial process shapes like a somewhat laterally flattened cone. It is relatively broad at base, narrowing toward the apex, and is laterally compressed. The medial process is posteriorly directly, nearly horizontal. The paramere is removed from or barely reaching apex of the medial process. Furthermore, the phallus is elongated and slightly constricted toward the apex (not conspicuous in Z. gracilipes ). Zelus vagans and Z. gracilipes also resemble wasps to some extent, but both not as perfectly as seen in Z. errans and Z. vespiformis . Comparative views of male genitalia are shown in Fig. 11.

10. Zelus panamensis species group.

Zelus banksi sp. n., Zelus cordazulus sp. n., Zelus filicauda Bergroth, 1893, Zelus gilboventris sp. n., Zelus korystos Hart, 1986, Zelus nigromaculatus Champion, 1899, Zelus panamensis sp. n., Zelus truxali sp. n., Zelus varius (Herrich-Schaeffer, 1853) and Zelus xouthos sp. n.

This is another large group with ten species. Interestingly, most (seven) are new species. It is characterized by having an acute apical modification usually in the shape of a hook on the medial process and the conspicuous medial carination of the apical part of the dorsal phallothecal sclerite. The condition of the apical modification of the medial process differs from that in the Zelus armillatus species group in that it is much more prominent, usually acute and sometimes extending further ventrally. Rugulosity of the posterior pronotal lobe is highly pronounced relative to the other groups. Sexual dimorphism is pronounced in some species in this group (e.g., Z. gilboventris and Z. truxali ). Most species in this group are concentrated in southern Central America and northern South America. Comparative views of male genitalia and habitus images are in Figs 12, 13.

11. Zelus erythrocephalus species group.

Zelus auralanus sp. n., Zelus casii sp. n., Zelus chamaeleon Stål, 1872, Zelus erythrocephalus Fabricius, 1803, Zelus kartabenoides sp. n., Zelus kartabensis Haviland, 1931, Zelus laticornis (Herrich-Schaeffer, 1853), Zelus mattogrossensis Wygodzinsky, 1947, Zelus paracephalus sp. n., Zelus russulumus sp. n. and Zelus versicolor (Herrich-Schaeffer, 1848).

Two diagnostic characters identify members of this group. The medial process possesses a broad ridge-like projection or carina that initiates from the apex and extends ventrally or is removed from apex. The second feature is the apically oriented lateral sharp processes or projections on the dorsal phallothecal sclerite. These are not to be confused with the lateral expansion seen in the Zelus armillatus species group, where the direction of the expansion is laterad. In Z. auralanus and Z. versicolor , this process is short and somewhat dorsally directed, rather than apically directed. Three species, Z. kartabenoides , Z. kartabensis and Z. chamaeleon lack this structure. Their placement in this group is primarily based on the configuration of the medial process and the absence of characters of other groups. Also, the longitudinal ridge-like elevation or hook on the medial process is similar to the condition in another species, Z. laticornis , although the latter has a short modification. In this species group the parameres are usually somewhat bulbous and curved medially with moderate to long erect setae on the apical 1/2. The medial process is broadened at base, and usually anteroposteriorly compressed. Furthermore, the basal plate of the phallus is strongly curved in some members of this species group. Pronounced sexual dimorphism is seen in some species of this group. Notably, three species, Z. erythrocephalus , Z. paracephalus and Z. russulumus have purple, blue or greenish iridescence on the membrane of the hemelytron. Species of this group show a predominant southern South American distribution, with a few found only from the Amazons. Comparative views of male genitalia and habitus images are in Figs 14, 15.

Because of the heavy emphasis on male genitalic characters for grouping species, four species described only from females are not placed in any of the species groups defined in the above. These are: Zelus fasciatus Champion, 1899, Zelus plagiatus (Signoret, 1852), Zelus sphegeus Fabricius, 1803 and Zelus means Fabricius, 1803. Zelus fasciatus is similar to the females of some of the species in the Zelus panamensis species group and also occurs in an overlapping geographical region (southern Central America). Zelus plagiatus and Z. sphegeus show resemblance to the females of Z. versicolor , which is in the Zelus erythrocephalus species group. Zelus means , by possessing a rounded humeral angle and spinelike setae, aligns most closely with the Zelus vagans species group and the Zelus longipes species group. A future cladistic analysis, including morphological and molecular data, is needed to test the monophyly of these species groups and may also have the potential to place these female-based species.

Species removed from Zelus

Five species are removed from Zelus : Z. araneiformis , Zelus gradarius Bergroth, 1905, Z. modestus ( Stål, 1862), Zelus subfasciatus Stål, 1860 and Zelus vittaticeps Stål, 1866. These species represent an undescribed genus "Hartzelus" and will be treated in a separate study. They will be listed as Harpactorini incertae sedis until their generic placement is formally clarified.