Heterosternuta phoebeae Wolfe and Harp

Wolfe, G. William & Harp, George L., 2003, A New Species Of Predaceous Diving Beetle, Heterosternuta Phoebeae (Coleoptera: Dytiscidae), From The Ozark Mountains Of Arkansas, The Coleopterists Bulletin 57 (2), pp. 117-121 : 117-120

Heterosternuta phoebeae Wolfe and Harp , NEW SPECIES.

Diagnosis. Heterosternuta phoebeae is characterized by the following combination of characters: presence of dense thickened setae just anterior to procoxae ( Fig. 4 ), aedeagus sclerotized just above the base across dorsal surface, relatively fine metacoxal punctation ( Figs. 9–10 ), pronotum and elytra with large fascia ( Fig. 11 ), ventral surface yellow to brownish, relatively large size (3.8 mm to 4.2 mm), and distinctly trifid structure of the aedeagus ( Figs. 1– 2 ) which is bizarre and totally unique within the genus.

Derivation of Name. This species is named in honor of Phoebe Harp.

Description. Males. Size and Shape. (N 17) length 3.8–4.1 mm (average

3.9), width 1.9–2.0 mm (average 2.0), length to width ratio 2.0–2.1 (average 2.0). Elongate oval, widest at middle, pronotum and elytra in continuous outline. Lateral margins of pronotum evenly

rounded toward anterior angle.

Prothorax. Lateral bead distinct, at widest point approximately equal to

118 THE COLEOPTERISTS BULLETIN 57(2), 2003

width of an antennomere. Thick, dense setae distinctly evident on prosternum ( Fig. 4 ) in front of procoxae. Prosternal process lanceolate, prominence distinctly angulate and somewhat produced, prosternal file composed of transverse ridges.

Pterothorax. Metasternal process interlocking on mesosternum. Metacoxal lines approximately parallel but slightly diverging anteriorly.

Abdomen. First visible (divided) abdominal sternite approximately one third length of second. Second sternite large, subequal in length to next three combined. Cluster of a few elongate setae evident on medial posterior edge of some sternites.

Coloration. Shining dorsally ( Fig. 11 ). Head and antennae light orangish to orange-brown. Last antennomere very slightly infuscate. Pronotum with even broad dark band along anterior margin; disc and lateral areas orangish; posterior margin without dark band or barely perceptible narrow band in medial extending along elytral

third. Elytron with sutural stripe distinct, anteriorly THE COLEOPTERISTS BULLETIN 57(2), 2003 119

base then expanding back to form small basal fascia, posteriorly gradually expanding to form small subapical fascia; middle fascia large, undulating along anterior and posterior edges, variably connected to sutural stripe and posterior fascia. Ventral surface orangish-brown; metasternum and metacoxae slightly more brownish.

Microsculpture. Head finely punctate, punctures separated by 1 to 2 puncture widths. Punctures a little finer and more irregular in size anteriorly. Pronotal punctures fine and sparse, finer and sparser discally; densest paralleling anterior margin. Elytral punctation ( Fig. 7 ) relatively fine and sparse, punctures separated by 3 to 5 times the width of a puncture. Elytral reticulation mostly a pentagonal/polygonal network. Metacoxal punctation ( Fig. 9 ) moderately coarse, punctures separated by 1 to 3 puncture widths. Metasternal punctures approximately twice as coarse as metacoxal punctures.

Protarsus. Protarsomere with 2 rows of slightly modified palettes. Anterior and posterior protarsal claw distinctly bent at base; anterior claw ( Fig. 5 ) sinuate along inner margin and slightly shorter than posterior claw.

Genitalia. Aedeagus ( Figs. 1–2 ) distinctly trifid at apex, sclerotized just above the base across dorsal surface. Paramere ( Fig. 3 ) tapering toward apex, apex blunt with evident setae. Ventral margin slightly serrate.

Female. (n 26) Length 3.7–4.2 mm (average

4.0), width 1.7–2.1 mm

120 THE COLEOPTERISTS BULLETIN 57(2), 2003

(average 2.0), length to width ratio 2.0–2.2 (average 2.0). Similar to male except: punctation slightly finer and denser ( Figs. 8, 10 ); microreticulation more transverse producing a duller appearance. Protarsomeres narrower, without modified palettes, claws evenly arcuate and tapering. Valvulae ( Fig. 6 ) somewhat quadrate shaped, apex with dense short setae and a few long setae, ventrally with short spines and a few long setae.

Type Data. The holotype male and allotype female are labeled: Searcy Co. AR. Bear Ck. at US Hwy 65 30/ V/88 Harp. The primary types and 43 paratypes (from the same locality, Fig. 11 ) are deposited in the senior author’s collection .

Taxonomic Remarks. Specimens of H. phoebeae key to couplet 5 in Matta and Wolfe (1981). Specimens of H. phoebeae are 0.1 mm to 0.5 mm larger and have distinctly finer metacoxal punctation than members of H. ohionis (Fall) and H. jenniferae (Wolfe and Matta) . H. phoebeae is included in the key to Heterosternuta in Wolfe (2000) in couplet 5 as Heterosternuta new species.

Specimens of H. phoebeae are of similar size to larger members of Heterosternuta such as H. diversicornis (Sharp) , H. wickami (Zaitzev) , and H. oppositus (Say) . Specimens of H. phoebeae are easily distinguished from specimens of H. diversicornis because the former do not possess ventral pubescence between the metacoxal lines. Ventral coloration of specimens of H. phoebeae is yellow to brown, while that of H. wickami is almost uniformly black. Unfortunately, ventral coloration of specimens of H. oppositus varies from almost black to orange thus specimens are best distinguished from those of H.

Figures

Figs. 1–6. Selected structures of H. phoebeae n. sp. 1) Aedeagus, dorsal view of trifid apex, arrow indicates sclerotized portion at outer angle (100); 2) aedeagus, lateral view, arrow indicates position of sclerotized portion at outer angle (80); 3) paramere, lateral view (80); 4) ventral view of head and prosternum (anterior leg removed), arrow indicates dense thick setae (60); 5) male anterior protarsal claw (500); 6) valvula (200).

Figs. 7–10. Punctation and microsculpture of H. phoebeae n. sp. 7) Male elytral punctation and reticulation (800); 8) female elytral punctation and reticulation (800); 9) male metacoxal punctation (80); 10) female metacoxal punctation (80).

Fig. 11. Habitus and known distribution of H. phoebeae n. sp.; square indicates the type locality.