Heteronychocassis acuticollis Spaeth, 1915

Simões, Marianna V. P. & Sekerka, Lukáš, 2014, Redescription ofHeteronychocassis acuticollisSpaeth, 1915 (Coleoptera: Chrysomelidae: Cassidinae), The Coleopterists Bulletin 68 (3), pp. 407-410 : 407-410

Heteronychocassis acuticollis Spaeth, 1915 ( Figs. 1–9 )

Heteronychocassis acuticollis Spaeth, 1915: 286 (original description); Blackwelder 1946: 747 (catalog); Monrós and Viana 1949: 426 (catalog); Borowiec 1999: 166 (catalog); Borowiec and Moragues 2005: 263 (catalog).

Redescription. Measurements: Total length 8.7 mm; greatest elytral width 7.7 mm; pronotal length 2.0 mm; greatest pronotal width 5.5 mm. Body ( Figs. 1–2, 4 ) subtriangular, around 1.2X longer than wide. Integument glabrous, except for extremely short setae and sparse setae on pronotum and ventral side. Ground color brown with anterior margin of pronotum, midregion of elytral margin, and elytral disc brownish yellow and antennomeres V–XI dark brown and I–IV light brown. Antenna with scape, pedicel, antennomeres II–III glabrous with sparse, long setae, IV–XI with long, dense setae. Length ratio of antennal segments 100:40:60:84:68:76:85:68:68:84:132, with XI tapered towards apex. Interocular distance 1.3X wider than widest width of eye. Coronal suture deep. Eyes ( Fig. 5 ) subrounded, around 2.05X longer than wider. Frontoclypeus ( Fig. 5 ) as wide as long, open and elevated at the apex, depressed medially with short, complete epistomal suture and incomplete midsuture; labrum ( Fig. 5 ) medially elevated, with sinuous anterior margin. Pronotum ( Fig. 1 ) trapezoidal, 2X wider than long, with sharp sides; anterior margin continuous, covering the head completely in dorsal view; lateral margins sharp; basal margin bisinuate and posterior angle truncate; disc convex, with shallow depression close to posterior angle, and finally punctate. Prosternum glabrous and smooth, with narrow elevation; process ( Fig. 5 ) 1.5X longer than wide, apex depressed and rounded. Mesosternum glabrous; mesosternal process deeply notched; mesepimeron with exposed portion closing mesocoxal cavity. Scutellum seemingly triangular. Elytra continuous with pronotum, slightly longer than wide, with the widest region at the anterior third; basal margin smooth; anterolateral angle rounded and projected anteriorly. Humeri smooth and round ( Fig. 6 ), moderately protruding. Disc regularly convex, with 2 shallow principal impressions at anterior third close to suture; in dorsal view, coarse punctation in discontinuous rows, with fine, disordered punctation in the intervals, denser close to suture and principal impressions; in lateral view, humeri followed by deep and straight notch and row of coarse punctures. Explanate elytral margins moderately broad, in the widest part half the width of disc, smooth and shiny. Epipleura ( Fig. 7 ) continuous, with 2 deep cavities, 1 short anterior to deep notch following the humeri, and another after, not reaching apex. Metasternum smooth, with midregion elevated. Sternites length ratio 100:66:60:60:66. Legs sparsely and finely setose at tibial apex; trochanters triangular, with sparse and short setae; femur slightly wider and grooved at anterior half, with sparse, long setae; tibia longer than femur, wider towards the apex, densely setose. Tarsomeres with long, dense setae; I with subparallel lateral margins, II–III bilobed, with long, sparse setae. Proclaws ( Fig. 8 ) with single large, basal tooth, meso- and metaclaws ( Fig. 9 ) asymmetrical, with inner claw half the length of outer.

Geographic Distribution. Fr e nc h G u i an a ( Spaeth 1915).

Material Examined. Holotype ( Figs. 1–9 ) (by monotypy), glued: ‘ Guyane Française ∣ Charvein [white, printed and cardboard label] ∥ Type [pink, printed and cardboard label] ∥ Archard ∣ don. 14 ∥ acuticollis ∣ m. Typ. unic! ∣ Spaeth det. [white, printed and cardboard label] ∥ Manchester Museum ∣ Holotype [pink, printed and cardboard label]’.

Type Locality. Charvein (circa 5°34.5′ N, 53°53.7′ W, 10–30 m elevation.) is a former French prison named Camp Charvein situated in Mana commune, arrondissement of Saint- Laurent-du-Maroni in French Guiana .

Discussion and Conclusions. Chapuis (1875) erected the group Batonotites, composed of a single genus Batonota Hope, 1840 , that later would be split into several genera ( Spaeth 1923). He defined Batonotites as having the metepisternum distinctly separated from the metepimeron by a stria and possessing simple tarsal claws basally approximated and thus barely divergent. The supplemental characters used by Chapuis included: convex body; pronotum inserted in the notch at the anterior margin of elytra; prosternum slightly projecting anteriorly; elytra with a spinose projection; and metepisternum distinct.

Maulik (1916) divided Batonota into three genera based on the general shape and form of the dorsal spine: Batonota (species with trapezoidal scutellum, long dorsal spine, and lateral sides of the elytra concave), Akantaka Maulik, 1916 (species with trapezoidal scutellum, short dorsal spine, and lateral sides of the elytra straight), and Trikona Maulik, 1916 (species with triangular scutellum and very deeply punctate elytra).

Spaeth (1923) summarized the characters which separate Batonota (sensu lato), made note of the structure of tarsal claws as unique within all Cassidinae (sensu Spaeth), and revised the genera close to Batonota . As a result, he downgraded Akantaka to a subgenus of Batonota and additionally described a new genus, Paratrikona Spaeth, 1923 , for species included formerly in Trikona (later recognized as a junior objective synonym of Omoteina Chevrolat, 1836 ), with the exception of Trikona humeralis (Olivier, 1808) , and provided a key to the genera.

Later, Monrós and Viana (1949) proposed a new substitute name, Dorynotini, for Batonotites because the latter was based on a junior synonym, and they included seven genera: Akantaka (now considered as a subgenus of Dorynota Chevrolat, 1836 ), Dorynota (senior objective synonym of Batonota ), Eremionycha , Heteronychocassis , Omoteina , Paranota Monrós and Viana, 1949 , and Paratrikona . Since that time, the name Dorynotini has had prevailing usage and was conserved by all subsequent authors (e.g., Hincks 1952; Borowiec 1999). Monrós and Viana (1949) characterized Dorynotini as having the following combination of characteristics: head covered by pronotum; pronotum inserted in a notch at the anterior margin of elytra; epipleura projecting; elytra with tubercle or spine projecting close to elytral suture; and tarsal claws parallel or slightly divergent, sometimes with one of them reduced or absent.

Monrós and Viana (1949) also provided a key to the genera of the tribe. In the key, the genus Heteronychocassis was characterized by the following combination of morphological features: subtriangular body, with the widest body width close to humeri; antennae with four basal antennomeres glabrous and seven pubescent apical antennomeres; head not visible from above; elytra without spinose projection; and each tarsus with a pair of non-divergent, asymmetrical claws. However, this does not correspond with the morphology of the type specimen of H. acuticollis , which exhibits protarsal claws with a single large, basal tooth, while the meso- and metatarsal claws are paired, asymmetrical, with inner claw half the length of the outer. Almost certainly Monrós and Viana did not examine the actual type specimen, because the Spaeth collection was at that time inaccessible. So they placed Heteronychocassis in the key based on the original description, which does not describe the protarsal claw as single. Hincks (1952) retained the genus within Dorynotini and used the structure of the tarsal claws as the main character to separate the tribe.

So far, Heteronychocassis is still known only from the holotype specimen, which was unfortunately heavily damaged during a loan (Lech Borowiec and Dmitri Logunov, personal communication). One of us (LS) salvaged the specimen in 2008 and glued all parts together to get an idea about the general shape and prevent future loss of fallen parts. Some legs and antennae were glued to a separate card pinned under specimen. Fortunately, the crucial morphological features for identification were preserved. The structure of the tarsal claws is typical for Dorynotini, with the meso- and metatarsi having two proximate claws, with the inner claw being shorter. The basally proximate asymmetrical tarsal claws are unique features within Cassidinae sensu stricto (otherwise, present only in several genera of Old World hispines) and thus most likely represents a synapomorphy for Dorynotini. Within Dorynotini, Heteronychocassis is unique, as it is the only genus which lacks a postscutellar tubercle or spiniform projection.

Figures

Figs. 1–9. Heteronychocassis acuticollis, holotype. 1) Dorsal habitus; 2) Ventral habitus; 3) Labels; 4) Lateral habitus; 5) Prosternum, ventral view, arrows indicate frontoclypeus and labrum; 6) Anterior margin of elytron, frontal view, arrow indicates smooth, rounded humerus; 7) Elytron, ventral view, arrow indicates epipleuron; 8) Protarsal claw; 9) Mesotarsal claw.