Pseudactium Casey, 1908

Owens, Brittany E. & Carlton, Christopher E., 2016, Collecting in the Museum: New Species, Taxonomic Changes, and Range Extensions of Euplectite Pselaphinae (Coleoptera: Staphylinidae) of the Southeastern United States, The Coleopterists Bulletin 70 (3), pp. 611-633 : 611-633

Pseudactium Casey, 1908

Diagnosis. Males. Head: Rounded trapezoidal, tempora broadly rounded behind ocular canthus to cervical constriction, vertexal foveae setose, frontal sulcus broad, shallow, delimited by foveae; antennal acetabula remote, antennomeres 1–8 unmodified, antennomeres 9–11 forming loose club; labrum of normal form for tribe, bearing pair of sensory pegs, mandibles broadly sickle-shaped, maxillae and labium typical for subfamily, labial palpi minute, 2-segmented, maxillary palpi unmodified, palpomere 1 minute and obliquely joined to palpomere 2, palpomere 2 pedunculate, narrower in basal 1/3, slightly expanded and rounded distally, palpomere 3 subtriangular, palpomere 4 widest, unmodified, bearing apical palpal cone; gula simple and slightly rounded anteriorly, paired gular foveae present; eyes present and well-developed, comprised of about 30 facets. Thorax: Pronotum cordate, disc evenly convex, antebasal transverse sulcus present, delimited by lateral antebasal foveae, longitudinal median sulcus absent, basolateral fovea present; prosternum slightly convex, lateral procoxal foveae present; mesoventrite with paired lateral and median mesoventral foveae, paired mesocoxal foveae present, mesocoxae contiguous; lateral metaventral foveae present, metacoxae conjunct; legs variously modified; elytra with sutural fovea and striae, antebasal discal foveae and subhumeral foveae present, discal striae very strong basally; lateroapical cleft present; wings present or absent. Abdomen: First visible tergite with small basolateral foveae; ventrite II bearing large basolateral foveae; ventrite III bearing lateral processes; ventrites IV–VI unmodified and afoveate; ventrite VII of males tripartite, lateral sclerites triangular, penial plate ovate and hinged basally. Aedeagus: Strongly asymmetrical, composed of basal bulb bearing 2 large distal processes, 1 usually elongate and originating along ventrolateral or ventral margin of phallobase and the shorter often digitate and originating along the lateral margin of phallobase or along dorsal aspect of elongate process.

Females. Externally similar to males except eyes smaller with fewer facets, secondary sexual modifications to the legs absent, and ventrite VII not modified into penial plate (revision, Carlton and Chandler 1994).

Notes. Members of the genus Pseudactium exhibit an interesting biogeographic pattern and have been identified as possible indicators of biodiversity in old-growth forests ( Carlton and Chandler 1994). Known species almost exclusively inhabit mature deciduous forests in the eastern US and occur south of Pleistocene glacial maxima. A number of species and collections are known from restricted localities within this range. Pseudactium copelandi Carlton and Chandler, 1994 , Pseudactium pecki Carlton and Chandler, 1994 , Pseudactium steevesi Carlton and Chandler, 1994 , and Pseudactium jaitlynum new species appear endemic to localities in northern Alabama, and Pseudactium magazinensis Carlton and Chandler, 1994 and Pseudactium ursum Carlton, 1995 are known only from the type localities in Arkansas. The existence of some species and disjunct populations in Tennessee, Pennsylvania, and Texas may indicate sites of past refugia and long-term persistence of stable forest habitats. Pseudactium stannardi Carlton and Chandler, 1994 is known only from the holotype that was collected in a forested loess soil habitat in northwestern Iowa east of the Missouri River. This represents a significant exception to the general distributional pattern of the genus. Attempts by the second author to collect additional specimens at or near the type locality during 2015 failed.

Herein we describe one new species and report range extensions for Pseudactium carolinae Casey, 1908 and Pseudactium mendicum ( Park, 1962) from forested areas in the eastern US. Pseudactium jaitlynum new species is described from a single specimen collected from a mature forest in Madison Co., Alabama. It is the fourth species known exclusively from the northern part of that state. Litter sifting in mature forests in north-central and southeastern Louisiana has documented two populations of P. carolinae and a single population of P. mendicum , constituting new records of the species for the state. A single collection record of P. carolinae from Fayette Co., West Virginia, and a single collection record from Great Smoky Mountains National Park in Sevier Co., Tennessee, are also new state records. Further targeting of known mature and old growth forest sites will likely yield new records throughout the eastern US for a number of Pseudactium species , and may shed light on the age and localized persistence of such habitats.

KEY TO MALES OF THE SPECIES OF PSEUDACTIUM CASEY (Modified from Carlton 1995)

1. Mesotrochanter and (or) metatrochanter modified, bearing acute spine or blunt tubercle, or distal angle prolonged beyond junction with femur...................................... 2

1′. Neither mesotrochanters nor metatrochanters bearing spines or tubercles, convex along ventral margin or at most arcuate-carinate............................................ 7

2. Lateral processes of ventrite III low and rounded or carinate, not obviously projecting beyond lateral margins of abdomen in dorsal view............................................... 3

2′. Lateral processes of ventrite III large, rounded triangular, obviously projecting beyond lateral margins of abdomen in dorsal view .............. P. parabolicum (Brendel)

3. Metatrochanter bearing an acute spine or blunt tubercle along ventral margin; ventral margin of mesotrochanter convex, angulate, or bearing an acute spine before distal angle ............................................................. 5

3′. Metatrochanter simple, ventral margin evenly convex; ventral margin of mesotrochanter concave, distal angle projecting beyond junction with femur..............................................4

4. Metacoxa unmodified, bearing at most a rounded flange anterior to trochanteral articulation; distal processes of aedeagus fused near phallobase, neither bearing distal digits.................... P. alexanderi Carlton and Chandler

4′. Metacoxa bearing a minute spine anterior to trochanteral articulation; shorter distal process of aedeagus arising midway along dorsal aspect of elongate process, bearing a cluster of digits and tubercles near apex......... P. pecki Carlton and Chandler

5. Ventral margin of mesotrochanter evenly convex or angulate near middle; lateral processes of ventrite III small, not reaching lateral margins of abdomen.......................6

5′. Ventral margin of mesotrochanter bearing an acute spine just before distal angle; lateral processes of ventrite III longer, reaching or slightly surpassing lateral margins of the abdomen .......................... P. carolinae Casey

6. Ventral margin of mesotrochanter angulate near middle; lateral processes of ventrite III smaller, less than ½ as long as ventrite III, barely visible................. P. steevesi Carlton and Chandler

6′. Ventral margin of mesotrochanter convex; lateral processes of ventrite III larger, 2/3 length of ventrite III... P. mendicum (Park)

7. Lateral processes of ventrite III larger, at least ½ length of ventrite III......................8

7′. Lateral processes of ventrite III minute, consisting of low, setose timidities near postlateral angle of ventrite III..................9

8. Each gena with 40 or more capitate setae ................. P. magazinensis Carlton and Chandler

8′. Capitate setae on each gena of head 30 or fewer ....................... P. copelandi Carlton and Chandler

9. Capitate setae on each gena of head 40 or more; protrochanters arcuate along ventral margin ...................... P. stannardi Carlton and Chandler

9′. Capitate setae on each gena of head 20 or fewer; protrochanters variable along ventral margin......................................................10

10. Aedeagus with digitate accessory process arising from dorsal aspect of elongate process near base, distally bearing numerous small and two larger digits clustered at apex ........................ P. arcuatum (LeConte)

10′. Aedeagus with digitate accessory process arising near right side of phallobase, bearing lateral row of two larger and many smaller digits, distally ( Fig. 11 )................... ............. P. jaitlynum Owens and Carlton , new species

Figures

Fig. 11. Pseudactium jaitlynum, aedeagus, dorsal view.