Revision of Bledius. Part 4, Classification of species groups, phylogeny, natural history, and catalogue (Coleoptera, Staphylinidae, Oxytelinae). Bulletin of the AMNH ; v. 184, article 1
[New York] : American Museum of Natural History
"The purpose of this monograph is to review and reinterpret what is known about Bledius with the goal of prompting further study of the genus. Included are a new infrageneric classification for the world; discussions of the life cycle, habitat, distribution, enemies, chemical secretions, economic importance, immature stages, fossils, and phylogeny; and a cross-indexed annotated catalogue to the taxonomic names and associated literature. Formal taxonomic changes include the following: Bledius minniensis from Armenia is a new species, Neobledius is a new synonym of Bledius and Elbidus, and Microbledius and Psamathobledius are new synonyms of Bledius. New combinations include B. karachiensis transferred from Neobledius and actitus, litoreus, and playanus transferred from Microbledius. New names include albanicus and jutlandensis which replace the preoccupied nebulosus Koch and atlanticus Lohse, respectively. The following names are labeled as new status: B. castaneipennis Mannerheim is elevated from synonymy with opacus Block; atramentarius Rottenberg is elevated from synonymy with and replaces bos Fauvel which was described a year later; limicola Tottenham is elevated from synonymy with and replaces germanicus Wagner which is preoccupied by germanicus Gravenhorst; minor Mulsant and Rey is elevated from synonymy with and replaces devillei Bondroit which was an unnecessary replacement name. Two names are emended: cariniceps for carinlceps and ghesquierei for guesquierei. Six names, bubalus Gistel, castaneus Mulsant and Rey, chimerinus Gistel, germanicus Gravenhorst, gyllenhalii Laporte, and westerhauseri Gistel are used herein for the first time since their original publication. All eight currently recognized subgenera are treated as synonyms of Bledius. In their place a classification of 34 species groups is proposed. This classification is based on examination of 422 of the 439 species of Bledius. The species were assigned to species groups based on examination of type material or subsequently identified specimens. Nine species were assigned to species groups from characters in the original description -- each such assignment is clearly indicated. Eight species are listed as incertae sedis for one or more of the following reasons: material was unavailable for study, the description did not cite sufficient information for placement in a species group, the types were lost, or the species was unknown. Descriptions, illustrations, a list of included species and localities, and a distributional map are provided for each species group along with a key to the group. No effort was made to define or revise species. The monophyly of Bledius is established by the presence of a cluster of secretory pores in a prosternal pit or depression and the possession in females of a pair of elongate, undivided genital sclerites on segment IX. Both Bledius and its sister genus Eppelsheimius have a central row of spine-like setae on the hypopharynx; they share other characters as well. The relationships among the species groups are shown in a cladogram on which many characters are homoplasic. Bledius comprises two main lineages. One with 14 species groups and 88 species includes, among others, the large robust species with horns. Most species of this branch live in saline habitats. Two of the species groups are restricted to the New World. The sister lineage includes the remaining 20 species groups and more than 340 species. A terminal cluster of species groups along with species in three other groups live in saline habitats; the others, including the four most speciose groups, live in freshwater habitats. In this lineage 3 species groups are confined to the New World, 11 to the Old, and the remaining 6 are widespread in both hemispheres. The primitive habitat for Bledius was near salt water. One descendent remains there; the other adapted to the freshwater habitat. In this second lineage some highly speciose groups developed near freshwater and there was a reinvasion of the saline habitat. Bledius is a large genus of 439 species, some of which occur in huge populations. Species are found on all continents except Antarctica and on most continental islands but are absent from most oceanic islands. Although only a third of the species lives in saline habitats (inland as well as coastal), these species represent two-thirds of the species groups. Two-thirds of the species live in freshwater habitats, representing the remaining third of the species groups. Bledius may have lived as far back as the Cretaceous. Nine fossil species have been described as belonging in Bledius, however, two of these are no longer included. Of the remaining seven only Bledius glaciatus from the Pleistocene and B. primitiarum of the Oligocene are likely to be Bledius. Another probable member of Bledius is Staphylinus lesleyi Scudder also of the Oligocene; this species has not been moved to Bledius. Although the oldest probable fossils of Bledius are about 35 million years old, evidence suggests that the Oxytelinae existed about 150 million years ago during the Jurassic. Species of Bledius are most abundant in unvegetated or lightly vegetated, sunny, moist sand adjacent to rivers, lakes, and oceans. They preferentially select their habitat based on soil moisture, salinity, texture, and, indirectly at least, size of the sand grains, availability of food, and amount of shade. The pressure of predators may influence habitat limits but that may be partly due to the physiological weakening of a Bledius that is not living in its optimal habitat. Although as yet undemonstrated, food plant specificity may influence habitat selection by Bledius. Bledius lives in burrows which adults excavate with their mandibles and strengthen with their protibiae. The burrows are several millimeters to about 40 cm deep and about 1 to 5 mm in diameter. Larvae also construct and live in burrows. Eggs are laid in special egg chambers; some species cache food in the burrow. The burrow serves not only as living quarters for Bledius but helps protect them. Bledius can live at a relative humidity of 100 percent to no less than 93 percent. The humidity within the burrow is nearly 100 percent. Some seacoastal species live in the intertidal zone where they remain during high tide. Individuals that stay in the burrow during high tide live in an air bubble, which acts as a physical gill, and are immediately active after the tide recedes. Individuals exposed directly to seawater fly away or survive by becoming comatose and recover only slowly when removed from the water; most, however, die after a few hours of immersion. Usually the adults overwinter in deep burrows. Eggs are deposited during spring or early summer and develop in two to three weeks. The larval stage lasts for six to eight weeks and the five instars are each of undetermined length. Pupae exist for about a week. Egg to adult then is two to three months. During the summer adults live for three to six weeks. Females oviposit several times; the number of generations per year is unclear but may vary according to species and climate. Larval characters have been published for 19 species. Adults and larvae feed on algae and diatoms that live in the moisture surrounding each sand grain. The green algae there are said to be stunted filamentous forms. Some Bledius facultatively store algae. Some species are said to exhibit subsocial behavior by attending to their offspring. Evidence for this interpretation is inconclusive. Carabid beetles of Dyschirius are regarded as the principal predators of Bledius. However, little evidence is found to support a species-specific host-prey relationship. More likely, the relationship of Bledius and Dyschirius is based on geographical distribution and habitat preference. Over 50 species of Dyschirius are reported with over 80 species of Bledius. Other Carabidae reported as actual or probable predators of Bledius include species of Cillenum, Bembidion, Pogonus, Dicheirotrichus, Clivina, and Schizogenius. The ichneumonid wasp, Barycnemis blediator, is a parasitoid of Bledius spectabilis. Sandpipers and rainbow trout also eat Bledius. Fungi of the order Laboulbeniales commonly infest Bledius and, although usually regarded as benign, one report suggests otherwise. Species of Bledius secrete a characteristic, penetratingly fragrant chemical of five components. That this secretion functions as a defensive chemical is debatable. No experimentally supported hypotheses have explained the function of this compound. One species in Japan was reported to do economically significant damage to clay beds used to produce salt by evaporation of seawater. The literature for and taxonomic names used in Bledius are summarized in a catalogue. Fifteen generic-level names have been used in Bledius; 646 species-level names have been used, 434 of which are presently listed as valid and extant. All names that have been included in Bledius are listed in the catalogue. The species names are cross-indexed and the references annotated"--P. 5-6.
367 p. : ill., maps ; 26 cm.
Includes bibliographical references (p. 335-355) and indexes.
Includes bibliographical references (p. 335-355) and indexes.