Pentamyrmex spinosus, Rider, David A. & Brailovsky, Harry, 2014

Rider, David A. & Brailovsky, Harry, 2014, Pentamyrmexini, a new tribe for Pentamyrmex spinosus, a remarkable new genus and species of Pentatomidae (Hemiptera: Heteroptera) from Thailand, Zootaxa 3895 (4), pp. 595-600 : 596-600

Pentamyrmex spinosus , new species

Description. The single female specimen upon which this description is based was glued onto a card. It has been removed from the card and is now pointed, but dried glue remains on the ventral surface, so characters of the rostrum and thoracic sterna are not visible.

Overall color black with a pale yellowish-white, triangular spot on each corium ( Fig. 1 ), a round, white, waxy spot on each propleurite and each metapleurite ( Fig. 2 ), and the coxae and basal portions of the femora pale yellowish-white.

Head gently curved downwards, declivant ( Fig. 2 ), sub-triangular, surface densely and coarsely punctate ( Fig. 3 ), except for a small roundish spot between each compound eye and adjacent ocellus, and an elongate linear area on each side running from just mesad of each ocellus onto base of each juga. Compound eyes pedunculate, distinctly raised above surface of head; ocelli relatively small, slightly tilted, giving impression that they are oriented anteriorly. Lateral margins of head relatively straight except for distinct notch just anterior to compound eyes, allowing for antennal insertions, margin distinctly reflexed around each notch and anteriorly for short distance; jugal apices obtusely, but narrowly rounded, extending distinctly beyond apex of tylus, but not meeting anteriorly. Antennal segment I brownish, remaining segments dark brown to fuscous; segments I, II, and most of III nearly glabrous, segments IV, V and the apical sixth of segment III with very short recumbent hairs; segment I very short, not nearly reaching apex of head, segment II slightly longer than I, segment III the longest, segment IV slightly longer than V, the diameter of segments IV and V becoming greater apically; each antennifer armed with large sublateral spine. Bucculae relatively wide, distinctly lobed posteriorly, each lobe protruding posteriorly slightly onto prosternum. View of rostrum obstructed by glue, but appears that it reaches to or slightly beyond middle coxae; segment I not reaching beyond posterior margins of bucculae.

Pronotum distinctly transversely constricted, dividing it into two sections, anterior section slightly longer along midline than posterior section ( Figs. 1 , 5 ), surface of both sections convex, not flat, densely and coarsely punctate; calli obsolete, slightly visible as elongate, longitudinal, C-shaped impunctate area ending just anterior to transverse pronotal depression. Anterior pronotal margin nearly straight, not reflexed (feebly ridged posterior to humeral angles); anterolateral pronotal margins rounded, not reflexed, shiny, impunctate, provided with a series of large spines; three spines anterior to pronotal depression, middle one the largest, posterior one the smallest ( Figs. 2 , 5 ); a single smaller spine posterior of pronotal depression; each humeral angle produced into very large, dorsolaterally oriented spine, itself provided with 3-4 smaller spines, and appearing bifid apically ( Figs. 1 , 5 ). Pronotum appearing somewhat broadly lobed over base of each corium, posterior pronotal margin arcuately concave along base of scutellum. Scutellum elongate, subtriangular, trispinose with large spine near each basal angle, and very large spine subapically ( Figs. 2 , 6 ). Basal scutellar spines oriented dorsally, each arising from conical elevation of scutellum ( Fig. 6 ), each slightly swollen near middle; subapical scutellar spine more robust, oriented dorsally and slightly posteriorly, longitudinally bifid apically ( Figs. 2 , 6 ). Basal area of scutellum swollen, densely and coarsely punctate, apical two-thirds of scutellum relatively flat, punctures much finer, sparse. Hemelytra much broader posterior to scutellar apex, finely and sparsely punctate, black, each with a large, triangular, pale yellowish-white spot on middle of mesocorium ( Figs. 1 , 5 ); clavi extending posteriorly as very narrow sclerite which meet beyond apex of scutellum; lateral hemelytral margins relatively straight anteriorly, then arcuately curved laterally beyond scutellar apex. Hemelytral membranes fumose with 5-6 weak longitudinal veins ( Fig. 5 ), juncture between corium and membrane diffuse, not well delineated, inner basal angles of membrane shiny brown.

Thoracic pleurites nearly vertical, black, except each propleurite and each metapleurite with a round, white, waxy spot; pleural punctures relatively fine, sparse, except somewhat more dense on propleura. Ostiolar peritreme small, auriculate, apex narrowly lobate, distinctly elevated above surface of pleurite, metapleural evaporative area very small, narrowly surrounding ostiolar peritreme, extending onto mesopleura, covering much of a sinuous, obtuse ridge running along posterior mesopleural margin which curves abruptly anteriorly running along dorsal mesopleural margin. Legs mostly black, coxae pale, extreme basal area of front femora pale, basal fourth of middle and hind femora pale; femora each with two pairs of small transverse teeth, the anterior tooth of each pair larger than posterior tooth which becomes obsolete on middle and hind femora; each femora also armed with dorsal apical spine ( Figs. 2 , 5 ), which is much larger on hind femora; hind tibiae distinctly curved apically.

Abdomen very large and bulbous when compared with head and thorax, rather uniformly, densely punctate. Connexiva covered by hemelytra, posterolateral angles not toothed or spinose, except that of segment 5 (4th visible) which is armed with a very large, dorsally oriented spine ( Fig. 2 ), and that of segment 6 (5th visible) has a small obtuse tooth. Spiracles very small, placed somewhat remote from lateral margins, especially on apical segments, each trichobothrial pair situated posterior to each spiracle, arranged longitudinally, or at a slight angle with the anterior hair slightly more mesad than posterior hair, both hairs of each pair located remarkably close to each other, nearly contiguous. Female genitalia ( Fig. 4 ) vertical, with basal plates relatively large, mesial margins straight, mesial dorsal angles rounded, dorsal margins concave, ending laterally in a narrow obtuse lobe, surface with a few coarse punctures and 2-3 wrinkles running at an angle from ventral margin; 8th paratergites subvertical, triangular, 9th paratergites typically formed, distally obtuse; second gonocoxae squarish, each with a small, obtuse, lateral tooth, 10th sternite squarish.

Measurements (in mm). Head length 1.12; width across eyes 1.57; interocular distance 1.09; interocellar distance 0.46. Length of antennal segments I-V, respectively: 0.35, 0.40, 1.08, 0.84, and 0.92. Pronotum: Maximum length of anterior lobe 1.16; maximum length of posterior lobe 1.09; maximum width of anterior lobe (without spine) 1.48; maximum width of posterior lobe (without spine) 1.96. Scutellar length 1.44; width 1.04. Total body length 6.30.

Type material: Holotype (♀), “Coll. I.R.Sc.N.B. / Thailand (Loei) / Na Haeo, malaise trap / 14-21.I.2001 / Leg.: P. Grootaert”, machine printed on light yellow label. Deposited in the Institut Royal des Sciences Naturelles de Belgique, Brussels, Belgium ( ISNB). The type specimen was originally mounted on a card; it has now been removed and glued to a point to allow for examination of characters of the venter. Some glue and paper remains stuck to the ventral surface. The left hind leg came loose from the body, and has been glued to the point. No paratypes. Male unknown.

Etymology. The specific epithet, spinosus , refers to the relatively large number of spines present on the thorax, abdomen, and legs of this insect.

Discussion. Ant mimicry is relatively common in certain hemipteran families (i.e. Miridae , Largidae , Lygaeidae sensu lato), but it has not previously been recorded in the Pentatomidae . We know of only one other genus that contains possible ant mimics, the genus Caridophthalmus Assmann. Caridophthalmus is primarily a New Guinean genus with a couple species occurring in northern Australia, and another reaching as far west as Timor. Its species are also black in color with a few spines and ivory marks, giving a vague resemblance to ants (the mimicry is not nearly as striking as in Pentamyrmex ). Caridophthalmus is currently placed in the Diemeniini which is characterized in part by a stridulatory area on the abdominal venter; this is lacking in Pentatmyrmex. The stridulatory region in Caridophthalmus is not as well defined as in the other diemeniines, and there are other significant differences. Placement of Caridophthalmus in the Diemeniini needs further study, but it probably deserves a new tribe to reside in. There are significant differences between Caridophthalmus and Pentamyrmex , however, and the two appear to be remotely related at best. Caridophthalmus has the head completely vertical, the eyes are distinctly pedunculate, the antenniferal tubercles are very different, the arrangement of spines and ivory marks are completely different, the armature on the legs is lacking, and the female genitalia is distinctly different.

One of the characteristics of Pentamyrmex deserves further comment. As stated above, the clavus continues along each side of the scutellum as a very thin (narrow) sclerite, the two eventually meeting just beyond the apex of the scutellum. Elongate clavi which meet posterior to the scutellum has not been recorded previously in the Pentatomidae . A similar condition has been recorded in some Acanthosomatidae , Cydnidae (Amnestinae) , Saileriolidae , Thaumastellidae , and Urostylididae ( Grazia et al. 2008) . The structure of the extended clavus in Pentamyrmex is quite different however, and may not necessarily indicate any type of relatedness. As described the Pentamyrmex clavus is very slender, nearly lineate, the two meet beyond the apex of the scutellum in more or less a point; the same structure in the above families is broader, meeting in a straight line beyond the scutellar apex.

Figures

FIGURES 1 - 4. Pentamyrmex spinosus n. sp.: 1, Body, dorsal view; 2, Body, lateral view; 3, Head, anterodorsal view; 4, Female genital plates, posterodorsal view.

FIGURES 5 - 6. Pentamyrmex spinosus n. sp.: 5, Body, dorsal view; 6, Scutellum, lateral view.