Akrobothrus ecuadoriensis, Barman & Michat & Alarie & Wolfe, 2007

Barman, E. H., Michat, M. C., Alarie, Y. & Wolfe, G. W., 2007, Figs. 16 – 17. 16 in A Description of the First Instar of Hoperius planatus Fall, 1927 (Coleoptera: Dytiscidae: Colymbetinae: Colymbetini), with Phylogenetic Implications, The Coleopterists Bulletin 24 (2), pp. 318-325 : 321-324

Akrobothrus ecuadoriensis , new species

( Figs. 1–4)

Type Material. Holotype, male; temporarily held in trust at USNM for MECN. Labeled with the following 2 labels: first, ‘‘ ECUADOR: NAPO Prov. Res. Ethnica Waorani, 1 km S. Onkone Gare Camp, Trans. Ent. 26 January 1994 220 m 00 ° 39 9 10 0 S 076 ° 26 9 W T. L. Erwin, et al.’’; second, ‘‘ Insecticidal fogging Terre firme forest Trans. 5, Sta. 4, Erwin – Lot # 653.’’

Type is missing left middle leg.

Allotype; female; deposited at USNM. Labeled with the following 2 labels: first, ‘‘ ECUADOR: NAPO Prov. Res. Ethnica Waorani, 1 km S. Onkone Gare Camp, Trans. Ent. 2 October 1996 220 m 00 ° 39 9 10 0 S 076 ° 26 9 W T. L. Erwin, et. al.’’; second, ‘‘ Insecticidal fogging Terre firme forest Trans. 5, Sta. 10, Erwin – Lot # 1710.’’

Allotype left antenna slide-mounted and retained with specimen.

Description. Elongate oval. Length 3.5 mm. Reddish brown color with pronotum darker than elytra.

Head. Frons ( Fig. 4 ) depressed between antennal insertions. A single, upwardly pointing, tubercle near the middle of the frons. Rostrum moderately produced. Eyes shallowly sinuate. Antennae ( Fig. 1) with club elongate, parallel-sided. Antennal club three segmented with first suture procurved and second suture recurved. Club densely and evenly pubescent throughout. Antennal scape with long setae, at least the length of scape or longer. Scape slender at base and bulbous towards apex. Funicle 7-segmented. Segments of funicle thickening towards antennal club. Funicle with sparse setae.

Thorax. Pronotum dorsally punctate. Punctures evenly distributed with an apunctate longitudinal line, the width of three punctures, spanning from the apex to base of the pronotum. Lateral margins of pronotum with a costate ridge. Procoxae prominent, globose and pubescent. Procoxal intercoxal piece with a transverse subcarinate ridge. The lateral edges of this ridge produced into points. Protibiae with bifid process on outer apical angle exceeding the inner apical angle. Meso and metatibiae with smaller bifid processes. Ventral sclerites densely and evenly pubescent. Metasternum with a row of tubercle-like setae along dorsal suture.

Abdomen. Elytra with strong depression beneath scutellum extending 2/3 the length of the elytral disc and the width of 3 interstriae on each side of the elytral suture. Scutellum spade-shaped, produced into a posterior point. Scutellum raised over the elytra depression extending above the elytral suture. Elytra deeply striate with 10 striae. Striae without punctures. Striae and interstriae shagreened. Interstriae each with a row of yellowish, squamose setae and rows of shorter, finer setae beneath these. Elytra granulate in appearance, with small, sparse punctuations on interstriae.

Allotype female identical to holotype except scutellum significantly smaller, not as spade-shaped, produced into a slight posterior point, but overall more transverse-oval in shape. Scutellum produced only slightly over the elytra. Frons ( Fig. 3 ) sexually dimorphic, more deeply concave, bearing a small row of setae on the epistoma, with a dense patch of setae forming an inverted ‘‘V’’ above this two sparser patches of setae on the frons along side the eyes and a longitudinal tumescence, medially at the apex of the frons. Protibae with a denser patch of setae at apex as compared to the holotype.

Etymology. This species is named ecuadoriensis (masculine) after the type locality.

Systematics

The costate lateral margins of the pronotum suggest that Akrobothrus is closely allied to Bothrosternus and Sternobothrus . Other characters, such as the presence of a lateral subcarinate ridge on the procoxal intercoxal piece indicate that, of these two genera, it is most closely related to Bothrosternus ( Table 1).

The Bothrosternina is in need of a modern systematic treatment. Such a treatment is likely to be confounded by the conserved morphology of this primitive group. Therefore, it is recommended that a systematic investigation include molecular characters in order to illuminate the phylogenetic relationships among the genera of Bothrosternina .

Natural History

Bothrosternina species are all myelophagous, with the exception of Bothrosternus and possibly Eupagiocerus ater Eggers , which are myelomycetophagous ( Wood 1986). Akrobothrus does not have an obvious fungal mycangium, although the function of the elytral pit and conspicuous male scutellum are unknown. Due to the sampling method used, no host data was obtained.

Figures

Figs. 3–4. Akrobothrus ecuadoriensis 3) female frons 4) male frons.