ARBOREAL BEETLES OF TROPICAL FORESTS: THE XYSTOSOMI GROUP, SUBTRIBE XYSTOSOMINA (COLEOPTERA: CARABIDAE: BEMBIDIINI). PART I. CHARACTER ANALYSIS, TAXONOMY, AND DISTRIBUTION
Authors: Erwin Terry L. 
Published: November 2009

A group of subarboreal tropical beetles, the Xystosomi of subtribe Xystosominanew subtribe, is revised and reclassified based on a reevaluation of structural characters. Xystosomi are found in tropical Australia (Queensland) and tropical/subtropical America (Guerrero, México, to Aguas Blancas, Argentina). The largest concentration of species occurs near the equator in the Amazon Basin, but a significant radiation of flightless forms was recently discovered in the northern Andes of Colombia, Ecuador, and Venezuela. Xystosomina also includes the Mioptachyi, which at present is composed of the generaMioptachysandInpa.Seventy-six species of Neotropical and Australian Xystosomi are described or re-described, illustrated, or keyed. This assemblage includes 12 classic species, 24 species described in the last 3 decades, and 40 new species, a 6-fold increase since the time of Henry Walter Bates, the last 19th-century entomologist to study this remarkable lineage of carabid beetles. The Xystosomi are now arrayed in five genera:Philipisgen.nov. (type:Tachys trunciDarlington, Australia),Geballusagen.nov. (type:Xystosomus microtretusErwin, Costa Rica),Gouletagen.nov. (type:Bembidion cayennenseDejean, Brazil),Batesianagen.nov. (type:Xystosomus grutiBates, Brazil), andXystosomusSchaum (type:Xystosomus inflatusSchaum, Brazil).The following specific taxa are described as new (type-locality in parentheses):Geballusarex(Brazil: 06°02′N 050°17′W),oligotreta(Panamá: 08°40′N 079°56′W),nannotreta(Brazil: 02°54′S 059°57′W),Gouletagentryi(Perú: 12°50′S 069°20′W),Batesianapara(Brazil: 01°22′S 048°20′W),angustia(Perú: 05°08′S 074°45′W),samiria(Perú: 05°08′S 074°45′W),esheje(Perú: 05°08′S 074°45′W),crassa(Perú: 03°15′S 072°55′W),notesheje(Perú: 03°15′S 072°55′W),manusculptilis(Perú: 12°07′S 070°58′W),parapara(Brazil: 02°28′S 046°26′W),am(Perú: 05°08′S 074°45′W),indetecticostis(Ecuador: 00°57′S 077°48′W),nox(Ecuador: 00°57′S 077°48′W),parkeri(Perú: 03°15′S 072°55′W),hamatilis(Ecuador: 01°02′S 077°40′W),notparkeri(Colombia: 00°08′N 075°51′W),pfunorum(Perú: 03°15′S 072°55′W),quadrata(Perú: 03°15′S 072°55′W),protosculptilis(Perú: 12°50′S 069°20′W),misahualli(Ecuador: 01°02′S 077°40′W),depressisculptilis(Ecuador: 01°02′S 077°40′W),irisculptilis(Ecuador: 00°24′S 076°37′W),foveosculptilis(Brazil: 02°28′S 046°26′W),punctisculptilis(Perú: 03°15′S 072°55′W),eugeneae(Perú: 11°56′47″S 071°17′00″W),anchicaya(Colombia: 03°43′N 076°57′W),jefe(Panamá: 09°12′N 079°21′W),exigupunctata(Perú: 05°08′S 074°45′W),rosebudae(Ecuador: 00°57′S 077°48′W),equanegrei(Ecuador: 00°57′S 077°48′W),henryi(Ecuador: 00°28′S 077°53′W),baeza(Ecuador: 00°57′S 077°48′W),huacamayas(Ecuador: 00°28′S 077°53′W),dannyi(Ecuador: 00°57′S 077°48′W),alticola(Colombia: 04°21′S 074°22′W),jacupiranga(Brazil: 24°42′S 048°00′W),chiriboga(Ecuador: 00°15′S 078°44′W),wygo(Colombia: 04°53′N 074°31′W).The following names are resurrected from synonymy for good species:hilarisBates andbeltiBates. Several name combinations were changed as a result of the generic reorganization:Philipis trunci(Darlington),Geballusa microtreta(Erwin),G.polytreta(Erwin),Gouleta notiophiloides(Erwin),G.spangleri(Erwin),G.cayennense(Dejean),Batesiana bisulcifrons(Erwin),B.negrei(Erwin),B.hilaris(Bates),B.belti(Bates),B.ampliata(Bates),B.strigosa(Bates),B.gruti(Bates),B.nigripalpis(Erwin),B.villiersi(Perrault),B.apicisulcata(Erwin),B.iris(Erwin),B.sculpticollis(Bates),B.sulcicostis(Bates),B.anterocostis(Erwin),B.ovatula(Bates),B.grossipunctata(Erwin),B.batesi(Erwin),B.seriata(Erwin),B.sublaevis(Bates),B.aetholia(Erwin),B.parainsularis(Erwin), NEW COMBINATIONS.Results of the Xystosomi character analysis provided impetus for a reanalysis of the classification of the major lineages of the more inclusive group, Bembidiini, to discover where the Xystosomi might belong and, in turn, if our understanding of the Bembidiini itself needed adjustment. These results are implied in Part I, but presented in detail in a separate paper, Part II. Phylogeny and Zoogeography, along with supplemental taxonomic information.