Axiagastus Dallas, 1851

Kment, Petr, Lemaître, Valérie A., Webb, Michael D. & Roca-Cusachs, Marcos, 2025, Revision of the Austro-Oriental shield-bug genus Axiagastus (Hemiptera: Heteroptera: Pentatomidae), with the description of five new species, and taxonomic notes on related genera, Zootaxa 5603 (1), pp. 1-82 : 6-14

Axiagastus Dallas, 1851

Axiagastus Dallas, 1851: 194 (key to genera), 221–222 (description of genus and type species). Type species: Axiagastus Rosmarus Dallas, 1851 , by monotypy.

Axiagastus : Walker (1867): 268 –269 (list of species); Stål (1868): 511 (redescription, key to genera); Stål (1876): 64 (key to genera), 94 (catalogue, distribution); Atkinson (1888): 128 –129 (catalogue, redescription); Lethierry & Severin (1893): 170 (catalogue, distribution); Distant (1902): 174 (key to genera), 179, fig. 107 (redescription, illustrations); Bergroth (1908): 172 (catalogue); Kirkaldy (1909): 126 (catalogue, distribution); Distant (1911a): 344 (list); China (1928): 191 (comparison with Indrapura ); Hoffmann (1932a): 8 (list); Tang (1935): 334 (catalogue); Stichel (1961): 764 (checklist); Stichel (1962): 244 (checklist); Gross (1976): 427 (discussion on relationship with Antestia group [= Antestiini]); Hsiao & Zheng (1977): 90 (key to genera), 132 (type species mentioned); Lin & Zhang (1993): 117 (key to genera); Cassis & Gross (2002): 458 (catalogue, distribution); Rider (2006): 259 –260 (catalogue, tribal classification); Arnold (2011): 42 (distribution); Fan (2011): 14 (key to genera), 71 (diagnosis, key to Chinese species); Arnold (2012): 55 –56 (taxonomy, distribution); Grazia & Schwertner (2017): 14 (plant association); Rider et al. (2018): 67 (mentioned in key to tribes), 74–75, 86 (comments on tribal placement), 97 (comparison with Critheus ).

Axagastus (incorrect subsequent spelling): Su et al. (1993): 282 (distribution).

Axiagaster (incorrect subsequent spelling): Arnold (2003): 24 (comparison with Indrapura ).

Axiasgastus (incorrect subsequent spelling): Lever (1934a): 2 (parasitoid, distribution).

Axigastus (incorrect subsequent spellings): Johns (1941): 4 (parasitoid).

Indrapura China, 1928: 190–191 (original description). Type species: Indrapura klossi China, 1928, by original designation. New junior subjective synonym.

Indrapura : Arnold (2003): 24 (comment on generic status); Arnold (2012): 55 (list).

Diagnosis (letters within parentheses correspond to those in the plates for each species). Medium-sized pentatomids (body length 10.62–15.39 mm) distinguished by the following set of characters:integument usually black or chocolate brown, with the exception of an orange colouration in A. mitescens and A. klossi comb. nov., with coarse, brown punctation, moderately large, white to stramineous spot of variable size on apex of scutellum; males with anterior apex of each buccula strongly produced into “tusk-like”, moderately elongate denticle ( Figs 3, 4, 50, 86, 120, 162, 203, 237, [d]); scutellum extending beyond two-thirds of abdominal length, postfrenal region slightly narrower than frenal region, with broadly rounded apex; mesosternum with low median carina (mc); ostiolar peritreme ( Figs 7, 8, 51, 87, 122, 139, 163, 204, 238 [p]) of external scent efferent system of metathoracic scent glands ruga-shaped, elongate, nearly of uniform width, with narrowly truncate, long apex reaching anterolateral area of metapleuron; abdominal segment III without projection or groove.

Redescription. Body of medium size, slightly longer than wide, convex dorsally.

Integument and vestiture. Integument coarsely and densely punctured, especially on scutellum, corium and connexivum, head and pronotum sometimes sparsely punctured; body glabrous dorsally and moderately pilose ventrally, particularly abdomen, labium and legs.

Structure. Head ( Figs 1–3, 49, 50, 85, 86, 119, 120, 138, 161, 162, 202, 203, 236, 237) slightly broader than long, rounded apically, more or less flat dorsally; mandibular plates as long as, or slightly longer than clypeus, broader than clypeus throughout their lengths, lateral margins, smooth and concave; apex of clypeus free; compound eyes globose; postocular portion short, situated in concave emargination of anterior margin of pronotum; ocelli placed in close proximity to posterolateral margins of compound eyes; antenniferous tubercles short, sessile near bases of antennae, completely visible in dorsal view; bucculae basally very narrow, gradually elevated anteriad, in females, about rectangular, without denticles anteriorly, in males, produced into a pair of elongate, strong, “tusk-like”, posteriorly curved denticles ( Figs 3, 4, 50, 86, 120, 162, 203, 237 [d]). Antennae with five antennomeres: scape (I) short, stout, extending to approximately apex of head, basipedicellite (IIa) shorter than distipedicellite (IIb), basiflagellum (III) shorter than distiflagellum (IV). Labium with length variable among species, labiomere I approximately as long as bucculae, labiomere III longest, length of labiomeres from shortest to longest: I<II<IV<III.

Thorax. Pronotum broad, anterior margin moderately emarginate around postocular portion of head, concave dorsally; anterior angles, each with a minute denticle, directed laterally; anterolateral margins obliquely straight; humeri rounded, not surpassing base of costal margins of forewings; posterolateral angles broadly rounded; posterior margin weakly concave. Scutellum elongate, distinctly longer than basal width, extending beyond two-thirds of abdomen; frenal portion as long as postfrenal portion, postfrenal portion narrower than frenal portion, tongueshaped. Thoracic pleuron and sternum. Prosternum impressed; mesosternum with low, obtuse median carina ( Figs 5, 239), terminating between mesothoracic acetabula; metasternum rather flat. External scent efferent system of metathoracic scent gland with large, oval ostiole ( Figs 51, 87, 122, 139, 163, 204, 238 [o]) directed posterolaterad, and elongate ruga-shaped peritreme ( Figs 7, 8, 51, 87, 122, 130, 139, 163, 204, 238 [p]) protruding beyond two-thirds of metapleuron laterally, nearly of uniform width throughout its length, with apex narrowly blunt or truncate; evaporatoria extensive on meso- and metapleura; each mesopleural evaporatorium covering most of posterior and lateral areas of mesopleuron (except oval polish spot near lateral margin); each metapleural evaporatorium large, anterolaterally bordered with an oblique, sinuate ridge, posterolaterally extending laterad, therefore metapleural evaporatorium appearing forked laterally. Forewings. Coria slightly surpassing apex of scutellum in resting position, with narrowly rounded posterolateral angles, each membrane with 8–10 longitudinal veins. Legs with femora unarmed, dorsal surface of each tibia with two longitudinal ridges enclosing a more or less flat surface; tarsi 3-segmented.

Pregenital abdomen. Ventrite III without median spine or tubercle; posterolateral angles of ventrites obtuse, unarmed; connexivum weakly exposed. Abdominal venter convex, neither grooved nor keeled.

Male genitalia. Genital capsule ( Figs 13–15, 23–26, 30‒33, 54‒57, 61–64, 79–82, 90–93, 97‒100, 123–126, 142–145, 166–169, 173–176, 180–183, 187‒190, 207–210, 214–217, 242–245, 249–252) subquadrate in dorsal view; dorsal rim more deeply incised than ventral rim; dorsal rim laterally slightly concave or obliquely straight, sometimes with indistinct serrations ( Figs 13, 23, 30, 97, 142, 166, 180, 187 [sr]), usually continuous in moderately angular projection contiguous with moderately deep and transverse emargination ( Figs 13, 30, 54, 61, 90, 97, 123, 142, 166, 187, 207, 214, 249 [te]) in middle of dorsal rim; ventral rim ( Figs 14, 31, 62, 91, 98, 143, 250 [vr]) broadly V-shaped in middle, infoldings of ventral rim deeply impressed on either side of moderately pronounced distension or small flap-like projection ( Figs 14, 31, 32, 52, 88, 125, 126, 140, 143, 164, 168, 189, 215, 251 [dn]) in middle, distension emarginated in middle; infoldings of ventral rim sometimes laterally (mesad to posterolateral lobes) with a narrow sclerotized black ridge with sawtooth-like projections ( Figs 13, 30, 187 [sp]), ending in a moderately pronounced, blunt denticle ( Figs 15, 32, 56, 63, 81, 99, 125, 144, 189 [dt]) or acuminate ( Fig. 216 [dt]), short, spine-like denticle ( Fig. 251 [dt]). Paramere ( Figs 16, 17, 27–29, 34‒36, 58–60, 65–67, 94–96, 101‒103, 127–129, 146–148, 170–172, 177–179, 184–186, 191‒193, 211‒213, 218, 219, 246–248, 253–255). Simple, crown with an upright finger-like process (flp) forming an acute angle with a laminate disc (ld), dorsal margin (dm) of parameral crown variable, apex acute or blunt/rounded in lateral view; stem (st) moderately elongate; apodeme (am) disc-like. Phallus ( Figs 18–20, 38–40, 68–70, 104–106, 131–133, 149–151, 194–196, 220–222, 256–258). Phallotheca weakly sclerotized, with a ventral convex projection (vcp) in close proximity with inner margin of processes of aedeagus (pa); 1–2 pairs of conjunctival processes (cp); aedeagus (ad) short, deflected dorsad, apex swollen, drop-like, transparent, with embedded phallotreme and a pair of elongate processes of aedeagus (pa), with shape varying among species.

Female genitalia. Terminalia ( Figs 41, 42, 71, 72, 107, 108, 152, 153, 197, 198, 223, 224, 259, 260). Valvifers VIII large, nearly quadrangular, with straight inner (mesial) margins and truncate or obtusely angulate inner posterolateral angles; valvifers IX short, narrow, transverse plate; laterotergites IX elongate, apically rounded; laterotergites VIII short, subtriangular, with convex outer margins, smooth caudal margins, without denticles or sometimes each with one short denticle. Gynatrium. Orifice of spermathecal duct surrounded by narrow, inverted U-shaped sclerite (us); ring sclerites (rs) rounded, with slightly pigmented brown outline. Spermatheca ( Figs 43, 73, 109, 154, 199, 225, 261). Spermathecal dilation long, regularly fluted; proximal spermathecal duct tubular, distal spermathecal duct gradually widened towards proximal flange; apical receptacle orbicular, with three ductules; length of ductules variable.

Etymology. Neither the etymology nor the gender of the names Axiagastus and Indrapura was provided in their original descriptions. The name Axiagastus is derived from the Ancient Greek adjective αΞΙΆγασΤΟΣ (= axiágastos), meaning “worthy of admiration, admirable”. The name Axiagastus should be treated as masculine according to Article 30.1.3 ( ICZN 1999). Indrapura is an old name for Mount Kerinci, a volcano located on Sumatra ( Anonymus 2024c) as well as a small city, Inderapura, situated east of the type locality Pasir Ganting ( Arnold 2003); the name should be treated as feminine according to Article 30.2.4 ( ICZN 1999).

Plant associations. The only species with well-known bionomics is Axiagastus cambelli , trophically associated with the coconut palm ( Cocos nucifera ) ( Arecaceae ) (for references, see the Biology section under A. cambelli ). Axiagastus cambelli has also been recorded on Areca ( Arecaceae ) in the Solomon Islands ( Lever 1933a, b, 1969; Cochereau 1964), although feeding on this plant has not been confirmed under laboratory conditions ( O’Sullivan 1973). In the laboratory, adult A. cambelli fed on the fruits of the cluster palm Ptychosperma sp. ( Baloch 1973). One paratype of A. votypkai sp. nov. from New Britain was also collected on a cluster palm (? Ptychosperma sp. ) (this paper). In the Ryukyu Islands, adults of A. yeshwanthi sp. nov. were frequently attracted to the seeds of Arenga tremula Becc. var. engleri Hatsusima ( Arecaceae ) (e.g., Yasunaga et al. 1993; Aoyagi 2014; in both studies, the species is referred to as A. rosmarus ). In addition, all the specimens of Axiagastus from the Philippines, in MRCC collection, were collected on unknown palm species. These records suggest that other Axiagastus species may also be associated with palms ( Arecaceae ). The record of A. mitescens from Fagaceae ( Zhang 1995, Hua 2000) requires further investigation.

Notes. Arnold (2003) wrote on the generic status of Indrapura : “Due to a number of characters it is so close to this genus [ Axiagastus ] that it could easily be inserted into it as a subgenus. Other characters, such as the shape of the female tergite VI (deep bulge on the posterior edge), suggest its position as an independent genus as justified. To clarify this question, however, significantly more material must be available, especially the males.” Reasons for the proposed synonymization: China (1928) described several distinguishing characters when he proposed the genus Indrapura , such as the length of the mandibular plates in relation to the clypeus (the clypeus is as long as the mandibular plates), the presence of a strong denticle at the apex of each buccula (a sexually dimorphic character), the elongate rostrum (reaching the base of the sixth ventrite), the pronotal width that is two and a half times the median pronotal length, the rounded humeri, the elongate ostiolar peritreme, the ventrites without a median furrow, the basal abdominal ventrite without a spine or tubercle, the unarmed legs etc. These characters, however, are not unique to Indrapura , but are instead shared with members of Axiagastus . The narrow and slightly elevated median longitudinal carina on the mesosternum, extending anteriorly between the forecoxae, is also found in A. yeshwanthi sp. nov. (described in this paper). Therefore, none of the characters listed by China (1928) is unique to Indrapura ; instead, the characters and their variability fall within the generic limits of Axiagastus . Consequently, based on the available evidence, the name Indrapura is here synonymized with that of Axiagastus .

For details on generic and specific synonymy within Axiagastini and a list of the included species, see Table 1.

Key to species of Axiagastus

1 Dorsum with ground colour reddish-orange to reddish-yellow with distinct black spots ( Figs 114, 134, 136)............. 2

– Dorsum with ground colour either coffee-brown to black with luteous spots or pale luteous or olivaceous yellow with black spots ( Figs 9, 21, 45, 47, 74, 83, 110, 117, 155–159, 200, 226, 229, 232, 234, 235).................................. 3

2 Labium long, reaching abdominal ventrite VII; yellowish-brown bugs with two submedian, divergent black fasciae on anterior area of pronotal disc; scutellum dark brown with six large, round, yellowish-orange spots (three basal spots, two located laterally before apex, and one at apex; Figs 114, 116)............ A. klossi ( China, 1928) comb. nov. ( Indonesia: Sumatra)

– Labium short, reaching metacoxae; yellowish-orange bugs with four small black spots arranged in transverse series on anterior area of pronotal disc; scutellum yellowish-orange with three large black spots (two rounded spots on scutellar disc anteriorly and one sublunate or arc-like spot before apex; apex of scutellum lacking pale spot ( Figs 134, 136)............................................................................................ A. mitescens Distant, 1901 ( China)

3 Dorsum uniformly coffee-brown with a distinct circular pale white spot at apex of scutellum ( Fig. 110).................................................................................. A. dubius Jensen-Haarup, 1937 (? Singapore)

– Dorsum either coffee-brown to black with luteous spots or pale luteous or yellowish-olivaceous with black spots......... 4

4 Parameral crown with apex gradually narrowed distally (apex of crown narrowly rounded in lateral view), and lateral margin with distinct obtuse angle in lateral view ( Figs 102, 103, 246, 253, 254).......................................... 5

– Parameral crown with apex abruptly narrowed distally (apex of crown needle-like or acuminate in lateral view), and rounded lateral margin in lateral view ( Figs 17, 27, 34, 58, 60, 65, 67, 127, 171, 172, 178, 179, 185, 186, 192, 193, 211, 213, 218)... 6

5 Apical margins of mandibular plates obliquely truncate (appearing angulate) ( Fig. 85); posterior margin of pronotal disc with more or less long black transverse band; mesosternal carina low, narrow; apex of scutellum bearing transversely oval white spot ( Fig. 83); median distension on infoldings of ventral rim of genital capsule emarginated into broad and shallow concavity ( Figs 91, 98)............................ A. chandrashekarai Salini, Kment & Roca-Cusachs sp. nov. ( Indonesia: Sulawesi)

– Apical margins of mandibular plates convex or rounded ( Fig. 236); pronotal disc uniformly coloured, black band on posterior margin of pronotal disc usually absent; mesosternal carina robust, high and wide ( Fig. 239); scutellar disc anteriorly with dark-brown to black round spots (sometimes confluent); apex of scutellum with transverse, anteriorly trilobate, whitish spot ( Figs 226, 229, 232, 234, 235); median distension on infoldings of ventral rim of genital capsule well pronounced, with narrow Vshaped emargination ( Figs 243, 250).................................................................................... A. yeshwanthi Salini, Kment & Webb sp. nov. ( China, Japan, Taiwan, India, Cambodia, Thailand, Vietnam)

6 Anterior pronotal disc with roughly round black spots arranged equidistantly in one or two rows ( Figs 9, 21, 155–159); narrow, sclerotized, black ridge possessing sawtooth-like projections inner to posterolateral angles of genital capsule ( Figs 13, 30, 187)................................................................................................ 7

– Anterior pronotal disc uniformly coloured and devoid of rows of black spots ( Figs 45, 47, 74, 117, 200); sclerotized, black ridge possessing sawtooth-like projections absent inner to posterolateral lobes.......................................... 8

7 Pronotal disc anteriorly with more or less fine, black punctures and four small, roughly round spots equidistantly positioned in a single row ( Figs 9, 21); dorsal margin of parameral crown not uniformly convex ( Figs 17, 27, 34).......................................................................................... A. rosmarus Dallas, 1851 ( Philippines)

– Pronotal disc anteriorly with coarse, black punctures and two rows each with four small, more or less well-defined roughly round spots positioned approximately equidistantly ( Figs 155–159); dorsal margin of parameral crown uniformly convex ( Figs 171, 172, 178, 185, 186, 192, 193)......................................................................................................... A. prathapani Salini & Kment sp. nov. ( India, Indonesia, Laos, Malaysia, Singapore)

8 Scutellum with frenal disc bearing moderately large, transverse, oval black spot in middle, and with more or less round, bright yellow spot at apex ( Fig. 117); median distension on infoldings of ventral rim of genital capsule well pronounced, tongue-like ( Figs 123‒126)........................................... A. luteipes Salini & Roca-Cusachs sp. nov. ( Myanmar)

– Scutellum with either uniformly black frenal disc except for basal margin ( Figs 45, 47), or with two quadrate spots sublaterally and narrowly or broadly crescent-shaped spot at apex ( Fig. 200; median distension on infoldings of ventral rim of genital capsule with narrow U- ( Figs 54, 55, 61, 62) or V-shaped ( Figs 207, 208, 214, 215) median emargination............... 9

9 Ground colour of dorsum mostly shining black with well-expressed bright yellow markings on pronotum and scutellum ( Figs 45, 47); apex of scutellum with only narrow, lunulate whitish spot; dorsal margin of paramere arc-like or uniformly convex in lateral view ( Figs 58, 60, 65, 67); median distension on infoldings of ventral rim of genital capsule sunken, emarginate with narrow U-shaped median emargination ( Figs 54, 55, 61, 62).............................................................. A. cambelli Distant, 1911 ( Papua New Guinea,? Australia [Queensland], Solomon Islands, Fiji, Samoa, Vanuatu)

– Ground colour of dorsum mostly ochraceous or bright yellow with well-expressed black markings on pronotum, scutellum and corium ( Fig. 200); apex of scutellum with whitish spot having approximately M-shaped anterior margin; dorsal margin of paramere not arc-like, rather convex or with broad angulation in lateral view ( Figs 211, 213, 218); median distension on infoldings of ventral rim of genital capsule with narrow V-shaped median emargination ( Figs 207, 208, 214, 215)............................. A. votypkai Salini & Kment sp. nov. ( Indonesia: Papua, Papua New Guinea, Australia [Queensland])