Siagotanyx Ashe, 2005

Ashe, James S., 2005, Three new genera and four new species of aleocharine staphylinids with unusually long mandibles from Australia (Coleoptera: Staphylinidae: Aleocharinae: Homalotini), Zootaxa 1002 (1), pp. 21-44 : 25-26

Siagotanyx Ashe , new genus

( Figs. 2 , 14–24 )

Type Species. Siagotanyx rufa Ashe , here designated.

Diagnosis. This genus can be easily recognized by the combination of: 4­4­5 tarsal segmentation; the extremely long mandibles with reduced prostheca, without modification to the internal base or molar area ( Fig. 16 ); the transverse labrum with anterior margin emarginate medially, greatly reduced setation, but with one pair of antero­lateral setae extremely long and whip­like ( Fig. 14 ); the distinctive labium ( Fig. 18 ), with ligula deeply divided to near base into 2 narrow, widely separated, pointed lobes, 2 discal setae, bases of discal setae widely separated, and wide but poorly defined medial pseudopore field with numerous pseudopores; and relatively short antenna with antennomeres 4 subquadrate and 5–10 transverse ( Fig. 20 ).

Description. Body generalized, slender, more­or­less parallel­sided, moderately flattened. Length 2.3–2.5 mm (known species). Head and prothorax very finely and uniformly covered with fine punctures and short, yellowish microsetae; elytra with moderatesized punctures and uniformly distributed yellowish microsetae; abdominal terga and sterna with longer and more prominent microsetae, uniformly distributed. Body without obvious microsculpture, glossy. Head subquadrate; eyes large, length in dorsal aspect about 0.7 times length of temples behind eye; temples broadly rounded behind eyes to base of head; neck absent; infraorbital carina present, complete, moderately well developed; antennal fossae very near lateral margins of clypeus, separated by lateral margins by less than 1/5 width of fossa. Antenna ( Fig. 20 ) moderately short; known species with article 4 subquadrate, 5–10 transverse, 11 slightly shorter than 9 and 10 together.

Labrum ( Fig. 14 ) transverse, separated from anterior margin of mentum by broad membranous area; anterior margin emarginate medially; setation reduced except one pair of antero­lateral setae very long and whip­like, oriented posteriorly in preserved specimens. Epipharynx as in Fig. 15 . Mandibles ( Fig. 16 ) with very long, curved and slender apices; right and left similar except right with very slight lobe in position of medial tooth; prostheca reduced with a few small teeth basally and a ciliate margin apically; internal base or molar area not modified into lobe. Maxilla ( Fig. 17 ) similar to Eumecognathus except lacinia broader and spines and spinose setae of the inner face of lacinia more densely arranged; maxillary palpi 4­articled, similar to that of Eumecognathus . Labium as in Fig. 18 ; ligula deeply divided to near base into 2 narrow, widely separated, pointed lobes, about 1/2 length of labial palpus 1; 2 discal setae, bases of discal setae widely separated; medial pseudopore field wide but poorly defined, without numerous pseudopores; lateral pseudopore fields each with setose pore, real pores, and about 13–16 pseudopores. Labial palpi 3­articled, first article subequal in length to next 2 together, article 2 and article 1 subequal in length, article 3 with 2 leaf­like sensory appendages apically. Mentum as in Fig. 18 .

Pronotum transverse, 1.5 times as wide as long in known species; uniformly covered with short, yellowish microsetae, microsetae posteriorly directed in midline and posterolaterally to laterally directed on each side of midline, without conspicuous macrosetae; integument with very slight, weak microsculpture, surface glossy. Hypomera narrowly visible in lateral aspect. Elytra about 1.2 times longer than prothorax; postero­lateral margins sinuate. Meso­ and metasternum as in Fig. 21 ; mesosternum faintly carinate medially at base; mesocoxal cavities fully margined behind; mesosternal process long, slender, pointed apically, extended beyond middle of mesocoxal cavities; metasternal process short, acutely rounded apically, not attaining mesosternal process, isthmus moderately long; known species with mesosternal process: isthmus: metasternal process in ratio of 1.7:0.7:0.9. Tarsal segmentation 4­4­5.

Abdomen parallel­sided, rounded apically. Known species with terga III–IV with moderate, V with slight and VI with inconspicuous transverse basal impressions; uniformly covered with moderately long microsetae. Surface without microsculpture, glossy.

Secondary sexual features: None obvious except males with anterior half of sternum VII with densely arranged micropores, and males with sternum VIII very slightly produced as a triangular lobe.

Etymology. The genus name is derived from the Greek noun “Siagon” (feminine) meaning “jaw” and the Greek verb “tanyo” meaning “stretch out” ( Brown 1956). It refers to the long, slender mandibles that characterize this genus. Gender: feminine.

Figures

FIGURE 2. Siagotanyx rufa Ashe, habitus dorsal, length, 2.4 mm.

FIGURES 14–18. Siagotanyx rufa Ashe. 14, labrum, dorsal aspect. 15, epipharynx. 16, right and left mandibles respectively, ventral aspect. 17, right maxilla, ventral aspect. 18, labium, ventral aspect. Scale bar = 0.1 mm.

FIGURES 19–24. Siagotanyx rufa Ashe. 19, mentum. 20, antenna. 21, meso­ and metasternum. 22, spermatheca. 23, aedeagus, paramere. 24, aedaegus, median lobe. Scale bar = 0.1 mm.