Agnosthaetus Bernhauer, 1939

Clarke, Dave J., 2011, A Revision of the New Zealand Endemic Rove Beetle Genus Agnosthaetus Bernhauer (Coleoptera: Staphylinidae), The Coleopterists Bulletin (mo 10) 2011, pp. 1-118 : 9-14

Agnosthaetus Bernhauer, 1939

Agnosthaetus Bernhauer, 1939: 213 . Type species: Agnosthaetus brouni Bernhauer, 1939: 215 (original designation).

Dimerus Broun, 1910: 15 (not as new, without authorship; name attributed to Fauvel in Broun 1912: 400; preoccupied, not Dimerus Fiori, 1900 ). Type species: none designated (2 original species: D. stilbus Broun, D. brouni Broun ); new synonym.

Agnosthaetus ; Blackwelder 1952: 42; Puthz 1978: 118, 1980: 20; McColl 1982: 13, 14, 20; Newton 1985: 206; Klimaszewski et al. 1996; Newton 1996; Leschen et al. 2003: 20; Puthz 2008: 59; Clarke and Grebennikov 2009: 347, fig. 1B, 348, 353, 356, 358, 363 (in adult key to genera), 364 (in larval key to genera), 364, fig. 5D, 366, fig. 7E, 368, fig. 9G, 369, fig. 10C-I, 370, fig. 11M, 371, fig. 12N, 374, fig. 15C, 381–382, 386–387, 390–393, 395.

Adult Diagnosis. Adults of species of Agnosthaetus may be distinguished from all other euaesthetine species by the combination of the following characters (modified from Clarke and Grebennikov 2009): head with gular sutures fused along length of neck constriction to submentum ( Fig.15 , gs), narrowly ovate to slit-like dorsal tentorial sulci ( Fig. 10 , dt), oblique antenno-ocular carina connecting antennal tubercle and eye ( Figs. 10–13 , ao, though effectively absent in Agnosthaetus ecarinatus Clarke , new species), and without subocular or other ventral carinae ( Figs. 15 , 63–65 ); antenna with well-developed 2-segmented club ( Fig. 17 ); apical labral margin toothed (e.g., Fig. 20 ) and adoral labral surface with distinct glandular pit ( Figs. 20–22 ); anterior margin of galea with distinct setiferous spine ( Fig. 18 , arrow); labium with elongate, sclerotized spines ( Fig. 19 , arrows); elytral epipleural ridge terminated at base of elytra, not deflected basodorsally nor continuous with elytral basal ridge ( Figs. 24 , ek, 85–88); and tarsal formula 5-5-4 ( Figs. 27–29 ).

Description of Adults. Habitus ( Figs. 1–8 ): Small, elongate, and wingless beetles, 2.5–3.5. mm long, with glabrous pronotum and elytra, and setose head and abdomen; generally reddish brown in color, occasionally with pattern of darker to nearly black pigmentation on head and/or thorax and some abdominal segments. Head capsule ( Figs. 10–12 , 14–15 ): Head transverse to suborbicular; with distinct lateral neck constriction ( Figs. 14–15 ); with only faintly impressed dorsal transverse nuchal impression, and with welldeveloped postoccipital nuchal plate ( Fig. 14 , np). Dorsum punctate (to almost impunctate in some species); setose (dorsally and ventrally); with two pairs of macrosetae ( Fig. 14 ). Dorsal tentorial sulcus present ( Figs. 10–12 , dt), in most species distinctly crescentic to narrowly ovate. Sublongitudinal ridge of head present ( Fig. 10 , sr). Antenno-ocular carina present ( Figs. 10, 12 , ao). Eye moderately large, occupying much of side of head; evenly rounded laterally (bulging anteriorly in some species); with numerous interfacetal ocular setae. Ommatidia circular and convex; posterior ommatidia with distinct central dimple. Postocular region noncarinate. Subocular region non-carinate. Submentum with subdued to well-defined transverse ridge ( Figs. 15 , 64 , str); with irregular line of small setae; and without any cuticular projections. Gular sutures fused posteriorly; abruptly diverging anteriorly from neck constriction. Postgena (and ventral neck) punctate, and with pair of (postgenal) macrosetae ( Fig. 15 ). Antenna ( Fig. 17 ): Antenna generalized in appearance; 11-segmented with loose but distinct two-segmented club; inserted at front of head, in front of anterior margin of eyes and mesal to mandibular articulations ( Figs. 10–11 ); with condyle of antennal scape concealed under poorly developed shelf (= antennal tubercle) ( Figs. 10–11 , 14 ). Antennal scape with pair of short but distinctly erect macrosetae ( Fig. 14 ). Antennomeres 1–7 elongate; 1 and 2 with length 1.2–1.4X width of 3–7; 3–7 elongate, 2.0–2.5X as long as wide; 8–9 subglobular, width subequal to or slightly greater than length (nearly subdiscoidal in some species); 10 with apex gradually tapering anteriorly from about middle, and with cluster of sensilla. Mouthparts ( Figs. 16, 18–22 ): Labrum transverse, narrow (width between 5–7X length); separated from cranium by narrow, clear, membranous or weakly sclerotized strip; with anterior edge dentate (reduced to only few teeth in males of A. newtoni and Agnosthaetus thayerae Clarke , new species), and dorsal surface with 6–7 pairs of macrosetae ( Fig. 20 ). Ventral (adoral) surface of labrum sclerotized but with large medial circular glandular pit ( Figs. 21–22 ). Mandibles falciform, long and slender ( Fig. 16 ); appearing generally symmetrical (but are asymmetrical in details; see below); each with one prominent tooth along inner edge (but see A. newtoni and A. thayerae ), and with mesal edges otherwise smooth (lacking serration). Mandibular molar lobe and prostheca absent. Mandibular chirality left superior (left mandible dorsal when mandibles closed). Left mandible ventrally with well-defined groove (to receive right mandible), and without a ventral tooth (but see A. newtoni and A. thayerae ). Right mandible with dorso-latero-ventral groove (to receive left mandible). Galea of maxilla anterolaterally with distinct setiferous spine ( Fig. 18 ); mesially with both slender setae and curved, roundended setae. Palpi 4-segmented (but often appearing 3-segmented); with setation consistently similar to Fig. 18 . Palpomere 3 longer than palpomere 2, distinctly fusiform, densely setose, and with cluster of digitiform setae on external side, 4 of which are minute, hyaline (or only weakly sclerotized, almost invisible with dissecting scope). Labium anteriorly with elongate sclerotized spines and with deep apicomedial notch ( Fig. 19 ). Inner edges of labial spines with two setae. Dorsal surface of labium with copious mesially directed cilia. Palpi 3-segmented, inserted widely apart (nearer sides than middle of labium). Palpomere 1 distinctly curved ventrally, longer than 2, and with 1–2 apical setae; 2 subfusiform, wider than 1, and with several long setae; 3 acicular. Mentum trapezoidal, up to 2.5X wider than long; with entire surface in same plane (palpomere rests absent); with 4 macrosetae. Internal and tentorial structures ( Fig. 14 ): Tentorial bridge present (tb). Corporotentorium present, split (cp); with arms projecting posteriorly (and thus in dorsal view difficult to discern from the welldeveloped tentorial walls). Nuchal plate with well-developed medial longitudinal phragma (ph). Prothorax ( Figs. 23–25 ): Pronotum oblong to slightly narrowed posteriorly; longer than maximum length of elytra; with 4 elongate, moderately to deeply impressed sulci (diverse in form); impunctate (except for macrosetal punctures in some species) and appearing glabrous but with sparse vestiture of extremely fine, long, and appressed setae (nearly imperceptible with dissecting scope). Pronotal macrosetation as in Fig. 23 . Base of pronotum with pair of small medial foveae (bf, confluent in Agnosthaetus nitidus Clarke , new species; more or less absent in A. vicinus and A. leviceps ), and up to several small basolateral foveae between base of medial and lateral sulci. Lateral prothoracic carina present ( Figs. 24 , 25 , pc); continuous with anterior pronotal margin (effaced posteriorly in A. bisulciceps , A. leviceps , and A. nitidus ); separate from basal pronotal margin. Pronotal hypomeron glabrous; impunctate and delimited ventrally by complete marginal ridge ( Figs. 24–25 ). Prosternum unmodified, without medial carinae or other special structures ( Fig. 25 ); punctate and setose (though impunctate in A. leviceps and A. nitidus ), and with surface parallel or subparallel to pronotum (lateral view). Anterior margin of prosternum broadly angulate medially; smooth (not dentate), and with pair of small erect macrosetae. Basal margin of prosternum with well-developed anteprocoxal lobes ( Fig. 25 , al), and straight to slightly arcuate anteprocoxal carina ( Fig. 15 , ac). Pterothorax: Scutellum broadly rhomboidal; mostly to entirely concealed by pronotum in dorsal view; with coarsely imbricate sculpture. Elytra ( Fig. 23 ) moderately convex dorsally, with sides broadly curving posteriorly; impunctate (except for macrosetal punctures in some species); appearing glabrous but with sparse vestiture of extremely fine, long, and appressed setae (as on pronotum); with 1–3 macrosetae (absent in Agnosthaetus kaikoura Clarke , new species and A. nitidus ); appearing fused at suture, but free from thorax. Elytral bases coarsely imbricate (as on scutellum); concealed beneath pronotum in dorsal view; with line of minutely setiferous foveae. Elytral sutural striae present (uniquely absent in A. leviceps ). Sides of elytra with distinct ridge extending from base to apex ( Fig. 24 , ek), and some species with marginal ridge ( Fig. 24 , mr). Metathoracic wings absent. Mesothorax generalized, without special carinae or other structures on mesoventrite ( Fig. 26 ); lacking externally visible pleural suture or ridge (evident only as internal oblique phragma); with distinct prepectal groove anterolaterally ( Fig. 26 , pg), and ventrolaterally with (posteriorly) distinct anapleural carina ( Figs. 24 , 26 , an). Mesothoracic intermesocoxal process broadly spiniform; ventral to metathoracic intermesocoxal process, and with apex contiguous with metathoracic process ( Fig. 26 ). Intermesocoxal fenestra present, such that mesocoxae are contiguous mesially. Mesocoxal cavity carina-delimited posteriorly. Mesothoracic apodeme straight to slightly curved ( Fig. 26 , ma); with apical muscle disc, and at least partly fused to mesoventrite. Mesocoxal cavity internally with vertically-projecting apodeme. Meso-metaventral suture absent (mesoventrite fused with metaventrite). Metathorax generalized, without carinae or other special structures on metaventrite; with broadly spiniform intermesocoxal process, and with small metaventral intercoxal lobes. Stem of metendosternite absent. Arms of metendosternite subcontiguous at base, and with unique dorsal branches arising from middle ( Fig. 26 , mt). Legs ( Figs. 27–29 ): Tibiae without external spines, only minute setae; with reduced apicoventral spines (length less than maximum width of tibia), and with comb of setae on each side of apex. Tarsal formula 5–5–4. Tarsi with all setae simple. Tarsomere 5 (on all legs) with simple claws and lacking empodial setae. Procoxal mesial surface excavate, with distinct carina-delimited groove ( Fig. 27 ). Protibia without linear comb of setae on ventral side. Mesocoxal mesial surface with small carina delimited groove. Metacoxa wider than long; contiguous medially or only very narrowly separated, and with mesio-basal surface straight (not notched). Posterior face of metacoxa oblique (to nearly vertical); with line of two to three macrosetae at edge ( Fig. 29 ). Abdomen ( Fig. 32 ): Abdomen subcylindrical; lacking carinae or other structures dorsally (except transverse basal carina of tergite III); and all segments without parasclerites. Segments III-VI each with tergite and sternite fused into solid ring. Intersegmental membranes elongate, visible when abdomen protracted, and attached preapically to preceding segment. Intersegmental membrane sclerites hexagonal, approximately equally sized. Spiracles of segments I and II placed in tergite. Segment II spiracle exposed in dorsal view. Sternites II/III with sharp intercoxal carina, without paramedial carina. Lateral carina of sternite III present ( Figs. 32 , 188 , lc), extending to or very near to apex of segment. Male: Sternite VIII ( Fig. 30 ) with apex deeply and broadly emarginate medially, and with 4 ventromedially curving macrosetae. Tergite IX entire, subequal in length dorsally to tergite X; expanded anteroventrally into broad projections ( Fig. 33 ). Tergite X articulated preapically with tergite IX ( Fig. 33 ). Sternite IX ( Fig. 37 ) with acutely produced or acuminate apex (and tip very slightly deflected ventrally); with 2 conspicuous macrosetae, and with 4–6 smaller macrosetae; (dorsally/internally) glabrous; (ventrally) evenly setose posteriorly, or with medial glabrous strip (in a few species). Aedeagus interspecifically very diverse in structure and setation (conforming to three basic types depending on configuration of a ventral membranous region: “ Type A” aedeagi (e.g., Figs. 94–97 ) with membranous region incompletely enclosed by sclerotization, continuous with basal bulb sclerite; “ Type B” aedeagi ( Figs. 148–151 ) with membranous region completely enclosed by sclerotization of the ventral part of median lobe, and is thus separated from the basal bulb sclerite. Aedeagus bilaterally symmetrical; in repose with median foramen facing dorsal side of beetle; with internal sac everting to ventral side of median lobe; and basoventrally with subcircular membranous region enclosing 2 areas of reinforced membrane. Basal bulb forming distinct hemispherical sclerite (varying in size among species). Apical part of median lobe developed into explanate lobe (or lobes; interspecifically variable in shape); with clusters of (usually) long shaft setae (absent in A. stilbus and A. minutus ), and with copious apical setation. Aedeagal parameres present; unilobed; interspecifically diverse in structure; lacking basal membranous joint; basally fused to median lobe (not articulating with it); with 4 setae near apex. Anterior portion of ejaculatory duct forming elongate tube lined with internal valvulae ( Fig. 36 ). Female: Sternite VIII ( Fig. 31 ) distinctly longer than tergite VIII; with apex sinuate medially; with central region of reticulate sculpture. Tergite IX divided medially ( Fig. 34 ). Gonocoxites I and II ( Fig. 38 ) distinctly separated by membrane. Second gonocoxites acutely pointed; without gonostyle; with finger-like membranous intergonocoxal projection (mip). Spermatheca comprising three distinct sclerotized portions and distal (sperm?) reservoir ( Fig. 35 ).

Larval Diagnosis. From known larvae of the subfamilies Euaesthetinae and Steninae , larvae of Agnosthaetus may be distinguished by the following combination of characters (modified from Clarke and Grebennikov 2009): head with distinct nuchal carina ( Figs. 40–41 , nu), strongly tapered posteriorly; nasale with four distinct teeth, the middle pair very elongate, without central tooth ( Fig. 47 ); first antennomere distinctly lageniform ( Fig. 48 ); antennal sensorium elongate, parallelsided, longer than last antennomere ( Fig. 48 , as); maxilla with distinct mala less than half length of first maxillary palpomere, and with two apical setae ( Fig. 44 , mal), and with line of three stout setae on adoral side; labium with pointed ligula, with four apical setae, without distinct palpiger ( Figs. 45–46 ). Prothorax with membranous anterolateral projection ( Fig. 49 , mm), cervicosternum undivided at middle ( Fig. 49 , cv); abdominal segment IX with distinct lateroventral, setiferous projections ( Fig. 56 , ar).

Description of Larvae. Habitus ( Fig. 39 ): Head capsule strongly sclerotized; yellowish brown; rest of body whitish with brown thoracic and abdominal sclerites, and with numerous, very long macrosetae. Head ( Figs. 40–42 ): Head very large, strongly transverse; widest at mandibular articulations; distinctly and evenly narrowing posteriorly; with nuchal carina visible dorsally and ventrally, obsolete medially ( Figs. 40–41 , nu); on both surfaces at base with distinct imbricate microsculpture. Dorsal ecdysial lines Y-shaped, with anterior arms of Y obsolete before antennal fossae, stem continuing to base of neck. Side of head with 6 stemmata, 5 visible dorsally and arranged in tight semicircular line ( Fig. 40 ), sixth somewhat ventrally removed from others and the only one visible in ventral view ( Fig. 41 ). Frons and labrum fused to form nasale ( Figs. 40 , 47 ). Anterior margin of nasale with 4 teeth (not including corners), without medial tooth; medial pair of teeth 2.5–3.0X length of paramedial teeth, separated by U-shaped emargination, and each with minute, slender seta-like structure at apex ( Fig. 47 ). Corners of nasale broadly triangular, bearing short, stout seta. Adoral surface of nasale simple, with 1 pair each of short setae and campaniform sensilla ( Fig. 47 ). Dorsal chaetotaxy as in Figs. 40, 42 . Antenna ( Figs. 40 , 48 ): Three-segmented; inserted mesal to mandibular articulation at front of head; directed anteriorly; articulating with head via greatly enlarged membranous ring ( Fig. 48 , me) subequal in length to first antennomere. First antennomere widest basally; distinctly lageniform; subequal in length or slightly longer than second antennomere; with 3 campaniform sensilla at apex. Antennomere 2 subparallel-sided; with 3 setae and single campaniform sensilla. Antennomere 3 as long as maximum width of 2; with 2 short and 1 very long setae and 2–3 elongate solenidia. Antennal sensorium slender; 1.5–2.0X length of antennomere 3; inserted dorsally at base of antennomere 3 (or membranous articulation between antennomeres 2 and 3; Fig. 48 , as). Ventral region of head anteriorly with broadly rounded submentum and partially open maxillary foramen, the former delimited posteriorly by faint line ( Fig. 41 ); with medial ecdysial line, splitting anteriorly in front of middle, terminating shortly before posterior tentorial pits. Ventral and lateral chaetotaxy as in Figs. 41–42 ; venter with 1 pair of large setae, 3 smaller pairs, and several inconsistently paired setae nearer sides; front of head with conspicuous campaniform sensillum near mandibular articulation. Mouthparts (as in Figs. 41 , 43–47 ): Mandible elongate, slender; dorsally with row of small blunt teeth appressed to inner margin; with 2 setae on basolateral surface ( Fig. 43 ). Maxilla as in Fig. 44 . Cardo small, slightly or distinctly notched laterally, bearing single small seta. Stipes large, sclerotized, with 2 setae on ventral side, 1 on mesal edge and 3 distinctly robust setae forming oblique line on dorsal surface. Mala distinct ( Fig. 44 , mal), approximately onethird to one-half length of first palpomere; bearing 1 small and 1 much larger seta; distinctly separated from stipes by sclerotized line. Palpiger forming thin, strap-like sclerite at base of first palpomere, bearing 1 small seta and distinct campaniform sensillum. Palpi 3-segmented. First palpomere columnar, without setae, but with campaniform sensillum near outer apex; palpomere 2 0.5X length of first, stout, bearing 2 setae and 2 campaniform sensilla; palpomere 3 acuminate, up to 1.5X combined length of first 2 palpomeres. Labial-mental complex as in Figs. 45–46 (2 different spp.); ventrally with distinct, weakly sclerotized premental area (or comprising thickened membrane; Fig. 46 , pm); with more strongly sclerotized, strap-like mentum bearing small seta at corners, and a subquadrate labium with pair of stout setae and 2 pairs of campaniform sensilla at base of palpi. Labial palpi slender, 2-segmented. First palpomere subequal in length to second; with large campaniform sensillum basomesially; second palpomere with extremely slender apical seta-like projection. Ligula short, narrowly pointed, the apex with pair of distinct campaniform sensilla, and with 2 pairs of slender setae, 1 each on ventral and adoral sides of apex. Adoral surface of labium with covering of toothlike projections. Thorax ( Figs. 39 , 49 , 50–52 ): Nota of thorax strongly sclerotized, with distinct medial ecdysial line and setation as in Figs. 50–52 . Chaetotaxy of meso- and metanota serially homologous; that of pronota differing both in numbers of macrosetae and campaniform sensilla and in arrangement of the latter (black dots in Figs. 50–51 ). Pronotum with 4 additional macrosetae on disc, and several others at margins. Thorax laterally with distinct but only weakly sclerotized pre-and posthypopleural sclerites, each bearing 2 small setae and 1 larger seta, respectively ( Fig. 39 ). Prothorax anterolaterally (between front corners of pronotum and prehypopleuron) with distinct membranous projection ( Fig. 49 , mm); ventrally with narrow, undivided cervicosternum (cv) bearing pair of minute setae at middle; with enlarged mesal extension of prehypopleural sclerites ( Fig. 49 , pr) in front of procoxa, with minute seta at apex. Sternal regions of both meso- and metathorax with pair of minute, weakly sclerotized plates, each with large seta. Mesothoracic spiracle large, annular, set on stout, membranous projection ( Fig. 39 , sp). Area beneath spiracle with faint sclerite bearing large seta ( Figs. 39 , 49 ). Abdomen ( Figs. 39 , 53–56 ): Abdomen with tergites entire, weakly sclerotized ( Fig. 53 ); at least sternites I-VIII completely divided ( Fig. 54 ), less sclerotized than tergites; single parasclerite on segments I-VII ( Fig. 39 ), each bearing 1 long and 1 (posterior) shorter seta. Abdominal tergal and sternal chaetotaxy as in Figs. 53–54 (respectively), serially homologous at least to segment VIII, but with sternite I having only setae S3–S5, tergite IX lacking any macrosetae ( Fig. 55 ), and sternite IX having 3 large macrosetae (of uncertain homology) ( Fig. 56 ). Membranous intersegmental regions with serially homologous patterns of campaniform sensilla. Spiracles present on segments I-VIII ( Figs. 39 , 55 , sp), annular, set on large, membranous, tubular extensions. Segment IX with short urogomphus, subequal in length to pygopod, and bearing a single very long apical seta, shorter subapical dorsal seta, and several other small setae ( Fig. 55 ); ventrally with distinct apicolateral projection bearing large seta ( Fig. 56 , ar). Pygopod (segment X) slightly shorter than segment IX; with single pair of large setae dorsally ( Fig. 55 ), and 1 or 2 pairs of setae ventrally ( Fig. 56 ); with pair of large campaniform sensilla both dorsally and ventrally, and with pair of eversible anal glands bearing numerous fine teeth and slightly larger hook-like setae ventrally.

Variation. Four larvae from different regions of New Zealand were studied in detail and formed the basis of the above description. The illustrations were based on a specimen from Southland and only minimal differences between this specimen and the others were noticed, including two specimens with only a single pair of macrosetae on sternite X, and some minor differences in labial ( Figs. 45–46 ) and head shape. Based on size (∼ 3.0 mm), two of the larvae were probably third instar .

Larval Material Examined. Probable species, if reliable, are given first, in parentheses. ( A. chiasma ). 35 adults, 2 larvae, NEW ZEALAND: South Island OL (Otago Lakes): Mt. Aspiring N.P., Haast Pass (SE of), 44°7′S 169°21′E, 600 m, Nothofagus menziesii forest, ANMT 739, 14.i.1985, litter, forest, Berl., A. Newton & M. Thayer, in FMNH ; 1 adult, 1 larva, Mt. Aspiring N.P., Makarora (12.5 km NNE of), 44°9′S 169°19′E, 370 m, Nothofagus menziesii -hardwood-podocarp forest, ANMT 740, 14.i.1985, litter, forest, Berl., A. Newton & M. Thayer, in FMNH . 1 larva, SL (Southland): Catlins Coastal Forest, head of Takakapa Valley, nr. Trig 18322, 280 m, 24.i.2006, washed soil, in JTNC. ( A. cariniceps ) . 1 adult, 1 larva. Takitimu Ra., Cheviot Face , 160 m, 30.i.1976, litter & moss, L. Deitz, in NZAC. ( Agnosthaetus aequalis Clarke , new species) . 1 adult, 1 larva. North Island: WN (Wellington): Wellington, Wilton’ s Bush , 41°15.963′S 174°45.159′E, 110 m, mixed broadleaf-podocarp forest, ANMT 1150, 24.xi.2005, berl., log & leaf litter, M. Thayer & A. Newton, in FMNH .

Biology. Based on collection data, Agnosthaetus beetles are nearly ubiquitously associated with leaf litter and soil habitats. Although the majority of records are from forested habitats, this at least partly represents a collection bias; many of the species have been found in both forested and nonforested ecosystems. In addition to general litter collections, mossy and particularly wet habitats seem also to be preferred. Many specimens have been taken from mossy stumps and logs by either processing sifted material from such habitats through Berlese/Tulgren funnels, or by extracting them via pyrethrum fogging.

Nothing specific is known about the diet, habits, or life history of Agnosthaetus beetles, although mandible morphology strongly suggests they are predatory. The occurrence of a few records on fungal fruiting bodies – where larvae of fungivorous insects occur – may also support this view. The peculiar sexual dimorphism of the labrum in many (and mandibles in some) species of Agnosthaetus is perplexing and is also known from several other species in Stenaesthetini . These features are unrelated to size, such as is widely known in the enlarged mandibles and heads of males from many other staphylinid groups, but seem to be either unique modifications in the male or separate modifications in both sexes (as in the brouni species-group: Figs. 113–119 ), and suggest that they may indicate a difference in dietary specialization between the sexes.

Distribution. Agnosthaetus beetles are widespread throughout the three main islands of New Zealand and close offshore islands; they occur from sea-level to high alpine environments and in a diversity of habitat types. The genus has not yet been reported from any oceanic islands in the New Zealand Region (Chathams, Norfolk, Three Kings, Subantarctic Islands, etc.). An analysis of the biogeographic patterns within the genus will be published elsewhere.

Nomenclature. Broun (1910, 1912, 1917, 1921) used the name Dimerus for the species he described that are now placed in Agnosthaetus . However, he attributed this name to A. Fauvel (first in 1910: 16), to whom he had sent a specimen of A. brouni (Broun) (see Broun 1912: 401). Fauvel had recognized that specimen as belonging to a new genus, Dimerus (see Broun 1912: 401), but he apparently never actually published this name. The name Dimerus , as used by Broun, has hitherto been overlooked (e.g., Scheerpeltz 1933; Blackwelder 1952; Herman 2001), probably because of its confusion with the senior homonym Dimerus Fiori, 1900 (Pselaphinae) . For example, Bernhauer (1939: 213) pointed out that this generic assignment was surprising as the specimens clearly belonged in Euaesthetinae (tribe Stenaesthetini ). For further details, see Remarks under the species A. brouni .

COMPARISON WITH OTHER GENERA

IN STENAESTHETINI

Agnosthaetus is one of three currently valid genera placed in the tribe Stenaesthetini Bernhauer and Schubert, 1911 , which are separated from other euaesthetines by the unique 5-5-4 tarsal formula. Tyrannomastax Orousset, 1988 was erected for two unusual species that probably belong in Stenaesthetus (see below), but which have strongly modified mouthparts ( Orousset 1988: figs. 415–416). In addition to the mouthparts, however, they differ from all other species of Stenaesthetus in having the tergite and sternite of abdominal segment III fused to form a ring. A fourth genus, Gerhardia Kistner, 1960 , was recently synonymized again with Stenaesthetus ( Puthz 2011) after having previously been placed in-and-out of synonymy with that same genus (see Puthz 2011). In addition to lacking the combination of characters mentioned in the diagnosis for Agnosthaetus , species of Stenaesthetus and Tyrannomastax are both well-differentiated from Agnosthaetus by: 1) the slender, nearly filamentous antennae with a weakly developed club; 2) a subocular carina; 3) an elytral epipleural carina that is dorsoventrally deflected at the base; 4) abdominal sternite III with a paramedian carina; and 5) male tergite IX indistinguishably fused with X (for more details see Clarke and Grebennikov 2009). The species of Tyrannomastax appear most closely related to Madagascan species of Stenaesthetus , but an in-progress phylogenetic analysis of Stenaesthetus will be needed to resolve the status of these species. Two undescribed species from Australia probably belong to a new genus (see Clarke and Grebennikov 2009, “EuaAUS”), but share some characters with Agnosthaetus , including similarly structured antennae, the presence of a similarly configured antenno-ocular carina, and a sublongitudinal ridge, as well as an anteriorly toothed labrum that shows sexual dimorphism similar to that seen in several species of the brouni species-group ( Figs. 113–114, 117–119 ). Other maxillary, labial, and segments IX-X characters are shared with Stenaesthetus . These two species can most easily be distinguished from Agnosthaetus by the completely smooth pronotum (lacking the medial and lateral sulci) and membranous rather than sclerotized labial processes. A full taxonomic treatment of these two species within a phylogenetic framework is currently underway.

KEY TO THE SPECIES OF ADULT AGNOSTHAETUS

BERNHAUER, 1939

Most of the major characters utilized in the key and ways to facilitate identification are explained under the above sections “Species Identification in Agnosthaetus ” and “Major Morphological Characters and Terminology”. Figure references are intended to illustrate particular character states, and the species illustrated may often not correspond to the species in hand. Numbers in parentheses before taxon names indicate the position of the species in the species descriptions section. To avoid repetition of parts of the key, couplets 25 and 45 refer back to earlier couplets (for groups of species keying out in two different places).

1. Metathoracic pleural ridge present ( Figs. 24 , mp)......................................... 2

1′. Metathoracic pleural ridge absent ( Figs. 85–86 )......................................... 30

2(1). Side of elytron with single distinct ridge ( Figs. 83–86 , ek)...................................3

2′(1). Side of elytron with two ridges ( Figs. 87– 88 , ek, mr; the second less distinct)....24

3(2). Mentum with distinct tooth at middle of basal margin ( Figs. 65–66 )...................4

3′(2). Mentum without distinct tooth at middle of basal margin ( Figs. 64, 67–68 )........7

4(3). Area above and behind antenno-ocular carina of head ( Fig. 11 , arrow) with one or several distinct subsidiary carinae formed by confluent punctures (e.g., Figs. 11–13 , 58, 60–62 ); base of pronotum with two distinct foveae at middle (e.g., Figs. 69–70, 74 , bf); dorsal tentorial sulcus of head distinctly slit-like ( Figs. 57–58 , dt), or very narrowly ovate ( Fig. 59 ) ............... 5

4′(3). Area above and behind antenno-ocular carina of head ( Fig. 10 , arrow) smooth, without distinct carinae (except for possibly distinct sublongitudinal ridge – Fig. 10 , sr; e.g., Figs. 10 , 59 ); base of pronotum with single fovea at middle, or two subcontinuous foveae (e.g., Fig. 77 , bf); dorsal tentorial sulcus of head not distinctly slit-like; broadly to very broadly ovate......................................................... 6

Figures

Figs. 14–20. Agnosthaetus brounides. 14) Head capsule, dorsal view; 15) Head capsule, ventral view; 16) Mandibles, dorsal view; 17) Right antenna, dorsal view; 18) Right maxilla, ventral view; 19) Labium, ventral view; 20) Labrum, dorsal view. Notes: A. brounides lacks the mo setae; circular dotted region between the mo setae indicates position of the adoral glandular pit, which from above is frequently visible as a darker region. Scale bars = 100 mm.

Figs. 10–13. Head capsules of Agnosthaetus spp. 10) A. stilbus; 11) A. rodmani; 12) A. brouni; 13) A. chiasma. Scale bars = 100 mm.

Figs. 63–68. Heads of Agnosthaetus spp., ventral view. 63) A. brouni; 64) A. stilbus, oblique view; 65) A. chiasma;

Figs. 23–24. Agnosthaetus cariniceps, thorax. 23) Dorsal view; 24) Left lateral view. Scale bars = 100 mm.

Figs. 25–29. Agnosthaetus brounides. 25) Prothorax, ventral view; 26) Pterothorax, ventral view; 27) Front leg, anterior view; 28) Middle leg, ventral view; 29) Hind leg, ventral view. Scale bars = 100 mm.

Figs. 1–8. Habitus photographs of Agnosthaetus spp. 1) A. brounides; 2) A. chiasma; 3) A. zonatus; 4) A. kaikoura;

Figs. 21–22. Agnosthaetus cariniceps. 21) Head capsule and labrum (other structures removed), ventral view;

Figs. 32–38. Agnosthaetus brounides. 32) Abdomen, ventral view; 33) Tergites IX and X of genital segment, male; 34) Same, female; 35) Spermatheca; 36) Ejaculatory duct; 37) Ninth sternite, male; 38) Gonocoxites, female. Scale bars = 100 mm.

Fig. 188. Agnosthaetus chiasma, abdominal segments III-IV. Scale bar = 100 mm.

Figs. 30–31. Agnosthaetus brounides, eighth sternite. 30) Male; 31) Female. Scale bar = 100 mm.

Figs. 94–97. Aedeagi of species in the Agnosthaetus brounides species-group, dorsal (left) and right lateral (right) views. 94) A. brounides; 95) A. chiasma; 96) A. bisulciceps; 97) A. rodmani. Scale bar = 100 mm.

Figs. 148–151. Aedeagi of species in the Agnosthaetus imitator species-group, dorsal (left) and right lateral (right) views. 148) A. imitator; 149) A. aorangi; 150) A. orongo; 151) A. stilbus. Scale bar = 100 mm.

Figs. 40–42. Larva of Agnosthaetus sp., head capsule. 40) Dorsal view; 41) Ventral view; 42) Lateral view. Scale bar = 100 mm.

Figs. 43–48. Larval structures of Agnosthaetus sp. 43) Left mandible, dorsal view; 44) Right maxilla, ventral view;

Fig. 49. Larva of Agnosthaetus sp., pro- and mesothorax, ventral view. Scale bar = 100 mm.

Figs. 53–56. Larva of Agnosthaetus sp., abdominal characters. 53) Tergite IV; 54) Sternites of segment VI;

Fig. 39. Habitus of the larva of Agnosthaetus sp., right lateral view. Scale bar = 1 mm.

Figs. 50–52. Larva of Agnosthaetus sp., thoracic tergites. 50) Pronotum; 51) Mesonotum; 52) Metanotum. Scale bar = 100 mm.

Figs. 113–120. Male (left) and female (right) labra of species in the Agnosthaetus brouni species-group, dorsal (anterior margin) view. 113) A. brouni; 114) A. tumidus; 115) A. aequalis; 116) A. akatarawa; 117) A. zonatus; 118) A. bicolor; 119) A. impressus; 120) A. nitidus. Scale bar = 100 mm.

Figs. 83–88. Pterothoraces of Agnosthaetus spp., right lateral view. 83) A. lanceolatus; 84) A. stilbus; 85) A. chiasma;

Figs. 57–62. Heads of Agnosthaetus spp., dorsal view. 57) A. vicinus; 58) A. heteromastax; 59) A. nitidus;

Figs. 69–74. Pronota of Agnosthaetus spp. 69) A. chiasma; 70) A. rodmani; 71) A. heteromastax; 72) A. stenomastax;

Figs. 75–78. Pronota of Agnosthaetus spp. 75) A. vicinus; 76) A. stilbus; 77) A. nitidus; 78) A. brouni. Scale bar =