Review of the Eustrophinae (Coleoptera, Tetratomidae) of America north of Mexico

Abstract The Nearctic fauna (north of Mexico) of Eustrophinae is reviewed, and consists of the following five genera and 12 species: Pseudoholostrophus (Pseudoholostrophus) impressicollis (LeConte), Pseudoholostrophus (Holostrophinus) discolor (Horn), Holostrophus bifasciatus (Say), Eustrophus tomentosus Say, Eustrophopsis confinis (LeConte), Eustrophopsis bicolor (Fabricius), Eustrophopsis brunneimarginatus (Dury), Eustrophopsis indistinctus (LeConte), Eustrophopsis arizonensis (Horn), Eustrophopsis ornatus (Van Dyke), Eustrophopsis crowdyi sp. n., and Synstrophus repandus (Horn). A lectotype is designated for Eustrophus brunneimarginatus Dury. A key is given to separate genera and species, supplemented with illustrations of relevant features, including aedeagi of all Nearctic species of Eustrophopsis. Detailed distribution (including Mexican records) and natural history data are provided.

Eustrophopsis was described by Champion (1889) based on his examination of specimens collected in the Neotropics. Specimens that possessed a notched prosternal process were separated from Eustrophinus Seidlitz and placed in Eustrophopsis. Nikitsky (1998) synonymized these two genera, stating that the emarginated prosternal character was not satisfactory to separate them. Therefore, Eustrophopsis became a senior synonym of Eustrophinus.
Natural history. Label data: Polyporus anceps (ME). Chantal (1985) stated that although no details were available for this species, it should probably be similar in habits and ecology to other members of the genus. Notes. As mentioned elsewhere, the very widely separated eyes of individuals of E. confinis seem to be unique within the genus, and are reminiscent of the condition seen in members of Holostrophini and Eustrophus.
Notes. According to LeConte (1873: 335), "the proper authority for this species is Say, its first describer; Mycetophagus bicolor Fabr. is probably a Platydema." Pollock (2008) mentioned that no other reference to Say being the author of this species could be found, and in fact, Say himself (1826) considered Fabricius to be the correct author.
Taxonomically, the separation of southern specimens of E. bicolor from those of E. indistinctus proved to be the most difficult problem in this study. Specimens of E. bicolor from northern and eastern North America are very distinctive from the southern specimens of E. indistinctus (color and dorsal punctation). However, as the ranges approach one another, distinguishing features between individuals of the two species become somewhat less conclusive.
Analysis of the male genitalia has revealed several consistent differences between E. bicolor (Figures 57, 63) and E. indistinctus (Figures 59,64), as follows: 1) tegmen relatively narrow in E. bicolor, with apical and basal piece subequal in length; relatively wider in E. indistinctus, with apical piece distinctly shorter than basal piece; 2) basal struts of median lobe long and narrow in E. bicolor, while shorter and wider in E. indistinctus; and 3) ring-like portion of sternite 9 U-shaped in E. bicolor, while Y-shaped in E. indistinctus (i.e. with a short basal extension).
There appears to be a rather narrow zone of sympatry between the two species, e.g. Roosevelt County, New Mexico and Randall County, Texas. Hybridization may be occurring in the southwestern United States; for example, multiple specimens from Hidalgo County, Texas seem to exhibit a combination of features of both species. Future studies using molecular methods may be fruitful in "fine-tuning" relationships between E. bicolor and E. indistinctus.
in the Nearctic region (see "notes", below); however, the marginal light markings are even more extensive than in E. brunneimarginatus.
Notes. Dury (1906a) described this new species based on two specimens, which differed from E. bicolor based on being smaller, broader, less shining, much less narrowed posteriorly, less distinctly striate, and the light colored border of the pronotum and elytra. However, in the next article in the same journal issue, Dury (1906b) seemingly synonymized his new species with E. confinis LeConte. These two species are quite different, however, and it is likely that Dury never examined actual specimen(s) of E. confinis.
A series of specimens from Hidalgo Co., Texas (TAMU) resemble E. brunneimarginatus, except that the marginal light markings are much more extensive on the pronotum and elytra. It is possible that these specimens represent E. marginatus Champion. In the description, Champion (1889) compared E. marginatus to E. bicolor, as E. brunneimarginatus was not yet described. Another species described by Champion (1889) -E. ovatus -possesses similar elytral and pronotal markings except that they are even more extensive than E. marginatus. I defer judgment on placement of the above mentioned specimens from southern Texas, as well as a possible synonymy of E. brunneimarginatus and E. marginatus, pending further study of the Neotropical eustrophines and detailed examination of Champion's types. Diagnosis. This is the only species of Eustrophopsis with a distinctly brown dorsal color; other diagnostic features include: antennomeres 1-4 and 11 not very distinctly contrasting in color with 5-10; eyes distinctly separated dorsally; pronotal punctation (especially compared with E. bicolor) relatively coarse.
Distribution (Figures 71,76). The range of this species is decidedly southwestern with most specimens from Arizona and New Mexico; southeastern Colorado is the northern extent. To the south, the species is known from northwestern Mexico. The 295 specimens examined were from the following jurisdictions: MEXICO: BAJA CALIFORNIA SUR, CHIHUAHUA. UNITED STATES: ARIZONA: Cochise, Gila, Graham, Greenlee, Maricopa, Pima, Pinal, Santa Cruz, Yavapai. COLORADO: Bent. NEW MEXICO: Bernalillo, Eddy, Roosevelt, Sierra. OKLAHOMA: Cimarron. TEXAS: Aransas, Blanco, Brewster, Cameron, Harris. (Complete label data given in Appendix 1).
Types. Eustrophus indistinctus LeConte. SYNTYPE, sex unknown, labeled "gold disk / Type 4779 / Eustrophus indistinctus Lec." Specimen with gold disk (indicative of California); the "Colorado" referred to in the description is actually the Colorado River, and not the state.
Natural history. Fungi (AZ); on bracket fungus (AZ); ex fungus on dying willow (NM); on dead log at night (NM); at night on fungusy logs (NM); at fungi on burned Populus snags (NM); fungi on Salix (AZ).
Notes. This species was one of the earliest described Nearctic eustrophines; however, it was synonymized early on with E. bicolor by Horn (1888: 34) who stated that "specimens collected by me in very early spring, in Arizona, have a decidedly brownish color above...These are probably merely less mature specimens as no other structural differences have been observed". This synonymy was followed by subsequent authors, e.g. Csiki (1924) and Poole and Gentili (1996). In fact, the relatively lighter coloration is one of the diagnostic features of adults of E. indistinctus. Therefore, E. indistinctus has been removed from synonymy with E. bicolor and re-established as a distinct species. There remains some difficulty in distinguishing southern specimens of E. bicolor from E. indistinctus (see "notes" for E. bicolor, above). ( (Horn). -Leng 1920: 238;Csiki 1924: 8;Blackwelder 1945: 495;Poole and Gentili 1996: 299. Eustrophopsis arizonensis (Horn). -Pollock 2008: 290. Diagnosis. This distinctive species may be diagnosed on the following combination of features: eyes moderately widely separated; prothoracic episterna with distinctly ru- gose macrosculpture; meso-and metatibiae with oblique ridges; distribution: western United States.
Distribution (Figures 72,76). Eustrophopsis arizonensis is one of the most widespread species in the subfamily, when the Mexican distribution is included. Specimens are known from northern United States (southeast Montana) south to Oaxaca, Mexico. Notes. The rugose nature of the prothoracic episterna of this species seems to be unique in the genus, perhaps in the entire subfamily. The Mexican specimens have been included in E. arizonensis, based on possession of this feature. Diagnosis. Individuals of E. ornatus share the following diagnostic features: antennomeres 5-10 distinctly widened, in males flattened on one side and with elongate, accessory setae; most specimens with at least faint indication of light elytral markings (seen in their maximum extent in Fig. 10). This species is a putative close relative of E.  blunter and more rounded than that of E. ornatus. Finally, specimens of E. ornatus tend to have antennae with contrastingly colored antennomeres, while antennomeres of E. crowdyi are more or less similar in color.
Distribution (Figures 73, 76). The Nearctic distribution of this species is restricted to southernmost Arizona and New Mexico; the range also extends south into Mexico. It is perhaps more widespread in Mexico and Central America, with the U.S. localities representing the northern extent of its range. The 132 specimens are from the following jurisdictions: MEXICO: JALISCO, SONORA. Notes. Van Dyke described this species as "ornatus" due to the presence of distinctive, lighter colored markings on the dark elytra. In fact, of all specimens of E. ornatus examined for this study (other than the types), only very few specimens exhibited this "typical" coloration. Many specimens had only a very faint indication of the lighter coloration, while others were entirely dark. The remarkably modified male antennomeres of this species and E. crowdyi is an indication of their possible close relationship. Diagnosis. Individuals of E. crowdyi may be diagnosed from other species of Eustrophopsis on the following characters: overall dark body color; eyes not approximate dorsally; males with short antennal sensilla; prosternal process rather blunt, rounded distally. As mentioned above for E. ornatus, that species and E. crowdyi are thought to be close relatives, based on the modified antennomeres of the males.
Legs all relatively similar in shape; metathoracic legs more elongate than meso-or prothoracic legs; all tarsi cylindrical, without ventral lobes; outer surfaces of meso-and metatibiae with numerous, oblique ridges; tibial spurs distinct, paired; tarsal claws slender, without basal tooth or expansion; male profemur with small, ovate, setiferous pit on ventral surface, approximately ¼ to 1/3 distance from base of femur.
Abdominal ventrites with uniform, relatively coarse punctation, setae decumbent; male genitalia darkly pigmented ( Fig. 62) with apical and basal piece of tegmen subequal in length; struts on median lobe elongate, relatively narrow, inner margins Vshaped; sternite 9 basally Y-shaped, with long stem. Distribution (Fig. 74). This species is known only from the type locality, in southeastern Arizona. UNITED STATES: ARIZONA: Cochise.
Natural history. All known specimens, except two, were collected using Lindgren funnel traps baited with western pine beetle (Curculionidae: Scolytinae) attractant; some specimens were labeled as having been collected near a scolytine-infested Chihuahua pine (Pinus leiophylla). Two specimens were collected at night under ponderosa pine bark. Derivation of specific epithet. I am very pleased to be able to name this new species after my oldest son, George "Crowdy" Pollock, who has accompanied me on many collecting expeditions and who has made many interesting discoveries along the way. In fact, he found larvae and adults of E. indistinctus in a neighbor's funguscolonized birch (Betula) stump, which were the first specimens of that species I had seen from New Mexico. Notes. Eustrophopsis crowdyi shares with E. ornatus conspicuously sexually dimorphic antennae, in males with a widening of antennomeres, one side of which is flattened and with setiform sensilla. While certainly not all world species of Eustrophinae have been studied in detail, this antennal modification is unique (so far) to these two species. As mentioned above, specimens of E. crowdyi were collected with many specimens of E. arizonensis and E. ornatus at the same locality in Cochise County, Arizona.   Diagnosis. This species is easily diagnosed based on the following features: body color uniformly dark; eyes narrowly separated; meso-and metatibiae smooth, without oblique ridges. Description (from Pollock 2008: 282). TL 5.6-7.0 mm; GEW 2.5-3.4 mm. Body ovate (Fig. 13), only somewhat tapered posteriorly, distinctly convex dorsally (Fig. 25); dorsal color dark piceous to black; antennae with basal 4 antennomeres dark rufous, distal half of antennomere 11 rufous; venter at least slightly lighter in color than dorsum; mouthparts similar in color to antennomeres 1-4; legs and abdominal ventrites dark rufous to piceous; dorsal pubescence relatively long, conspicuous; eyes narrowly separated ( Fig. 37), or almost contiguous (space < length of antennomere 1), medial mar- gin moderately emarginate; antennomeres 2-4 short, submoniliform; antennomeres 5-10 widened, becoming more triangular toward antennomeres 9-10; antennal sensilla completely annular; last maxillary palpomere unmodified, fusiform; prosternal process ( Fig. 49) triangular, narrowed distally, extended to slightly short of posterior margin of procoxae; prothoracic episternal suture absent; elytral punctation coarse, punctures arranged in longitudinal striae; meso-and metatibiae with scattered short spines, but distinct ridges absent; male lacking setiferous pit on ventral edge of profemur. Distribution (Fig. 75). Another widely distributed species, S. repandus exhibits a transcontinental range, similar to that of E. tomentosus. Most records are eastern, with a general gap in the interior of the continent, but with records from British Columbia, Pacific Northwest, and California.  Notes. Among specimens in the LeConte collection (MCZ) a specimen of S. repandus is labeled "Eustrophus concolor Linn." This is the only known instance of this name to me, and it seems doubtful that it represents a described species.

Discussion
The Eustrophinae is a good example of a group that is simultaneously rather obscure and poorly known to most coleopterists, and yet rather abundant, widespread and a conspicuous component of the saproxylic fauna associated with dead coarse, woody material. Saproxylic beetles are important members of the insect community associated with the dead tree habitat in most forest types; they can be associated with the dead wood itself, fruiting bodies of wood-decaying fungi, or with other saproxylic species (Hammond 1997). As indicated by Majka and Pollock (2006), few comprehensive studies have been done on the entirety of the saproxylic fauna of any region in North America. Saproxylic beetles undoubtedly have an important role in the ecology of forests, and likewise, forest structure and disturbance have a distinct effect on the presence (or absence) of saproxylics, including the Eustrophinae (Majka and Pollock 2006). Indeed, in forests where coarse woody material is allowed to persist (i.e., with limited management), eustrophines can be very common. However, this abundance can only be appreciated by collecting at night, on logs, snags or stumps infested by various groups of wood-rotting fungi. As well, Lindgren funnel traps have shown their value as collecting devices for very long series of eustrophines (see example in Introduction). Collecting on exposed surfaces during the day, or relying on black lights at night, will produce relatively few specimens; this is likely why there were relatively few very long series of specimens from single collecting efforts, seen among examined material for this study.
Biogeographically, the Nearctic fauna of Eustrophinae is an interesting combination of distribution patterns. Species of Holostrophini are either eastern or western; for example, individuals of Pseudoholostrophus impressicollis are restricted to westernmost North America, from southern British Columbia to California. Conversely, P. discolor is known only from northeastern regions. The range of Holostrophus bifasciatus is more extensive, but it is still restricted to the eastern United States and Canada; only a few records are known from west of the Mississippi River.
Specimens of Eustrophus tomentosus and Synstrophus repandus are among the most commonly collected in the subfamily, and have a transcontinental distribution with an interior gap. This relative paucity of specimens from the interior has much to do with lack of extensive forest habitats, except perhaps for forests associated with rivers. For example, a very large log along the Red River at Lockport, Manitoba yielded many specimens of S. repandus over a three-year period. This log was transported to its resting place from a location further south along the Red River during spring flooding. It is unknown whether the fungus (and consequent eustrophines) was post-depositional, or was initiated before the log rafted north. In any event, the relative shade and moisture of the riverbank allowed for the maintenance of the moisture critical to fungal growth and development of multiple generations of eustrophine beetles (both S. repandus and Eustrophopsis bicolor).
Species of Eustrophopsis exhibit a definite split between western and eastern faunas, except for E. confinis, which is the only species with a more or less continuous distribution across North America (admittedly, with relatively few known specimens); also, this species is restricted to northern latitudes, with specimens examined from more localities in Canada than the United States. The most common species of eustrophine, E. bicolor, is very widespread east of the central plains states, with only scattered re-cords from the western United States. In Canada, no records are known from west of Manitoba. Another eastern species is E. brunneimarginatus, which seems restricted to the southeastern United States, west to south-central Texas.
The most "complex" region for Eustrophopsis is the southwestern United States, especially Arizona. The forested mountains and canyons in southern Arizona represent a zone of sympatry for five of the seven species of Nearctic Eustrophopsis. Among these five, relatively few specimens of E. bicolor are known from the southwest. The vast majority of specimens of another western species, E. arizonensis, are known from Arizona and New Mexico, but specimens are also known from as far north as southeastern Montana. This species also has a Mexican range as far south as Oaxaca. Specimens of E. indistinctus are known mainly from New Mexico and Arizona, with a northern range limit in southeastern Colorado, and southern limit in Mexico. The two remaining species of Eustrophopsis: E. ornatus and E. crowdyi, are known only from southernmost Arizona and New Mexico, with E. ornatus extending south into Mexico as well. This preliminary analysis of Eustrophinae biogeography suggests that the Nearctic fauna is a mixture of elements with close relatives in Europe and/or Asia (e.g. Holostrophini, Eustrophus, and Synstrophus) or in the Neotropics (e.g. some southwestern U.S. Eustrophopsis).
While most genera of the Eustrophinae are relatively well known taxonomically (e.g. Pseudoholostrophus, Holostrophus, Eustrophus, and Synstrophus), the one group in need of detailed revisionary work is Eustrophopsis. Many species have been described from Neotropical and Afrotropical regions (including Madagascar), with more undoubtedly remaining to be discovered and/or described. This represents a complex biogeographic scenario, and at this point it is unknown (but perhaps doubtful) whether Eustrophopsis is a monophyletic taxon.
The seeming ecological importance of this group of tenebrionoid beetles, combined with the relatively high species diversity (especially in the tropics) make the Eustrophinae a group deserving of further research. Future work on the group should concentrate not only on the nomenclature and taxonomy of adults, but also on the collection and description of immature stages, and possible host preferences / associations between the eustrophines and the wood-decaying fungi in which they occur. This will contribute not only to a better, more robust classification of the Tetratomidae, but also to the overall phylogeny and evolution of the "lower Tenebrionoidea". or specimens include Blaine Mathison, Nikolai Nikitsky, Mike Ivie, Dan Young, Rich Leschen, and John Moser. Thanks to Harold Widener who allowed access to "Boone Draw" (Roosevelt County, NM), an excellent site for E. indistinctus adults. My wife Lisa and sons Crowdy, Henry and Louis accompanied me on more than a few trips to the forest, most of which became beetle-collecting opportunities. Yves Bousquet and Dan Young provided very useful, constructive suggestions on improving the manuscript. Finally, I thank Patrice Caldwell, Jo Laney, and the administration of Eastern New Mexico University for their continued support of faculty research and scholarly activity.

Appendix 1
Non-type specimen locality data for species of North American Eustrophinae