Eumecognathus 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 : 22-24

Eumecognathus Ashe , new genus

( Figs. 1 , 4–13 )

Type species. Eumecognathus tasmaniensis Ashe , here designated.

Diagnosis. This genus can be easily recognized by the combination of: 4­4­5 tarsal segmentation; the extremely long mandibles with greatly reduced prostheca, and a semicircular lobate internal base ( Fig. 6 ); the transverse labrum with greatly reduced setation, but one pair of antero­lateral setae extremely long and whip­like ( Fig. 4 ); the distinctive labium ( Fig. 8 ), with elongate, entire ligula, 2 discal setae, punctures of discal setae very close, and narrow medial pseudopore field without pseudopores; relatively short antenna with antennomeres 4–10 transverse ( Fig. 9 ); and transverse head and pronotum ( Fig. 1 ).

Description. Body generalized, slender, more­or­less parallel­sided, moderately flattened ( Fig. 1 ). Length 2.2–2.4 mm. Head, pronotum and elytra uniformly covered with fine punctures, short, yellowish setae, and reticulate microsculpture, surfaces appearing slightly asperate, abdomen obsoletely reticulate, surface glossy. Head transverse, 1.3 times as wide as long (width measured immediately behind eyes), antennal fossae distant from anterior margin by greater than width of fossa; eyes moderate in size, length less than length of temples behind eyes; temples behind eyes broadly rounded to base of head; neck absent; infraorbital carina present, moderately well developed; Antenna ( Fig. 9 ) moderately short; known species with article 4 subquadrate, 5–10 transverse, 11 about as long as 9–10 together.

Labrum ( Fig. 4 ) transverse, separated from anterior margin of mentum by broad membranous area; setation reduced except one pair of antero­lateral setae very long and whiplike, oriented posteriorly in preserved specimens. Epipharynx as in Fig. 5 . Mandibles ( Fig. 6 ) with very long, curved and slender apices, right and left similar except right with very slight lobe in position of medial tooth; prostheca greatly reduced with few small teeth basally and ciliate margin apically. Maxilla as in Fig. 7 ; galea slightly longer than lacinia in repose; apex of galea with membranous lobe, lobe densely covered with rows of short subspinose setae; anterior 1/5 of inner face of galea with row of long setae; lacinia with inner face of long spines and spinose setae; maxillary palpi 4­articled, article 3 slender, broadest near apex, about 1.3 times as long as article 2, article 2 relatively short, subequal in length to width of apex of article 3. Labium as in Fig. 8 ; ligula entire, rounded at apex, slender, about 2/3 length of labial palpus 1; 2 discal setae present, bases close, separated by about width of setal pore; medial pseudopore field narrow, without pseudopores; lateral pseudopore fields each with setose pore, 2 real pores, and about 6–7 pseudopores. Labial palpi 3­articled, first article almost as long as next 2 together, article 2 about 2/5 length of 1, article 3 about 1.4 times length of 2, with 2 leaf­like sensory appendages apically.

Pronotum transverse, 1.5–1.6 times as wide as long in known species; uniformly covered with short, yellowish microsetae, without conspicuous macrosetae; microsetae directed posteriorly in midline and postero­laterad laterally of midline; microsculpture moderately prominent, reticulate. Hypomera narrowly visible in lateral aspect. Elytra about 1.2 times as long as pronotum; postero­lateral margins sinuate. Meso­ and metasternum as in Fig. 9 ; mesosternum carinate medially in basal half, carina fading on base of mesosternal process; mesocoxal cavities fully margined behind; mesosternal process long, slender, pointed apically, extended beyond middle of mesocoxal cavities; metasternal process short, broadly rounded, not attaining mesosternal process, isthmus long; known species with mesosternal process: isthmus: metasternal process in ratio of 6:2:1.4. Tarsal segmentation 4­4­5.

Abdomen parallel­sided, rounded apically. Known species with terga III–IV with moderate, V with slight and VI with inconspicuous basal transverse depressions. Setation moderate with fine yellowish short microsetae, integument of known species with obsolete microsetae, surface glossy.

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

Etymology. The genus name is a combination of the Greek adjective “eumekes” meaning “of good length” and the Greek noun “gnathos” (feminine) meaning “jaw” ( Brown 1956). It refers to the long, slender mandibles that characterize this genus. Gen­ der: feminine.

Figures

FIGURE 1. Eumecognathus tasmaniensis Ashe, habitus dorsal, length, 2.3 mm.

FIGURES 4–8. Eumecognathus tasmaniensis Ashe. 4, labrum, dorsal aspect. 5, epipharynx. 6, right and left mandibles respectively, ventral aspect. 7, left maxilla, ventral aspect. 8, labium, ventral aspect. Scale bar = 0.1 mm.

FIGURES 9–13. Eumecognathus tasmaniensis Ashe. 9, antenna. 10, meso­ and metasternum. 11, spermatheca. 12, aedeagus, paramere. 13, aedaegus, median lobe. Scale bar = 0.1 mm.