PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASfflNGTON 109(4):73 1-743. 1996 Systematics, distribution, and host specificity of Edrabius Fauvel (Insecta: Coleoptera: Staphylinidae) James S. Ashe, Robert M. Timm, and Milton H. Gallardo (JSA) Division of Entomology, Natural History Museum, Snow Hall, University of Kansas, Lawrence, Kansas 66045, U.S.A.; (RJMT) Division of Mammals, Natural History Museum, Dyche Hall, University of Kansas, Lawrence, Kansas 66045-2454, U.S.A.; (MHG) Instituto de Ecologia y Evolucion, Universidad Austral de Chile, Casilla 567, Valdivia, Chile Abstract. — Systematics, distribution, and host relations of the amblyopinine genus Edrabius (Coleoptera: Staphylinidae) are reviewed. Herein, we recognize 1 1 species in the genus Edrabius, all of which are obligate associates of South American caviomorph rodents of the families Caviidae, Ctenomyidae, and Oc- todontidae (Mammalia: Rodentia), and restricted to the southern cone of the continent. Three new species are described: Edrabius grandis (host: Ctenomys coyhaiquensis and C. haigi); Edrabius australis (host: Ctenomys maulinus mau- linus); and Edrabius chilensiformis (host: Octodon degus). New distribution and host records are given for E. alticolus Seevers, E. argentinus Seevers, E. chilensis Scheerpeltz, E. peruanus Seevers, E. philippianus Fauvel, and E. weiseri Seevers. Occurrence of Edrabius on octodontid rodents is reported for the first time {E. chilensis from Aconaemys and E. chilensiformis from Octo- don). The genus Edrabius was formerly known to occur in association with various species of Ctenomys, with the exception of one species, E. kuscheli, associated with Galea musteloides (Caviidae). Resumen. — Se presenta una revision de la sistematica, la distribucion y las relaciones de los hospederos de los amblyopininos del genero Edrabius (Co- leoptera: Staphylinidae). Se reconocen 1 1 especies de Edrabius, todas parasitos obligados de roedores caviomorfos sudamericanos de las familias Caviidae, Ctenomyidae y Octodontidae (Mammalia: Rodentia). Se describen tres nuevas especies: Edrabius grandis, hospedador: Ctenomys haigi); Edrabius australis, hospedador: Ctenomys maulinus maulinus); y Edrabius chilensiformis, hospe- dador: Octodon degus). Se entregan nuevos registros distribucionales y de hos- pederos para E. alticolus Seevers, E. argentinus Seevers, E. chilensis Scheer- peltz, E. peruanus Seevers, E. philippianus Fauvel y E. weiseri Seevers. Por primera vez se reporta la presencia de Edrabius en roedores octodontidos {E. chilensis en Aconaemys y E. chilensiformis en Octodon). El genero Edrabius anteriormente se conocia solamente asociado a diferentes especies de Cteno- mys, con la excepcion de una especie, E. kuscheli, asociada a Galea musteloides (Caviidae). Perhaps the most interesting and enig- are unique members of the family Staphy- matic of all insect-vertebrate interactions linidae because of their obligate association are those of rove beetles of the tribe Am- with mammals; most of the 40,000 de- blyopinini (Coleoptera: Staphylinidae) and scribed species of staphylinids are free-liv- their mammal hosts. Amblyopinine beetles ing predators (Ashe & Timm 1987b). All 732 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON known species of amblyopinines have been most often found attached to the fur of mammahan hosts or in the hosts' nests. Six genera and more than 55 species have been described in the tribe Amblyopinini; five genera are restricted to the Neotropical re- gion and one is found in the Austrahan re- gion (Ashe & Timm 1988). Those restricted to the Neotropical region include: Ambly- opinodes Seevers, Amblyopinus Solsky, Chilamblyopinus Ashe and Timm, Edrabius Fauvel, and Megamblyopinus Seevers; a single monotypic genus, Myotyphlus Fau- vel, is restricted to Australia and Tasmania (Ashe & Timm 1988, 1995; Seevers 1944, 1955). Amblyopinines were, until recently, be- lieved to be obligate, blood-feeding ecto- parasites. However, the Central American Amblyopinus have a mutualistic relation- ship with their hosts rather than a parasitic one, and the conclusion that other ambly- opinines are parasitic is not supported by available evidence. Beetles living on vari- ous rodents that have different nesting bi- ologies show significantly different behav- iors, and nesting biology of the hosts un- doubtedly played a major role in the evo- lution of this mutualistic relationship (Ashe & Timm 1987a, 1987b, 1988; Timm & Ashe 1987, 1988, 1989). Hosts of amblyopinines are primarily cri- cetine and caviomorph rodents and South American marsupials. The evolution of this association is exceptionally interesting, both in terms of the ecology, evolution and biogeography of the beetles themselves, and also of the mammals with which they are associated. Members of each amblyopi- nine species are host specific, and members of the genera and intergeneric higher taxa have a tendency to be associated with a par- ticular group of mammals. Our concerted field efforts in recent years have uncovered a high degree of host specificity in these rather large, active beetles (Ashe & Timm 1987a, 1995; Timm & Ashe 1987, and see below). One of the most poorly known of the am- blyopinine genera is Edrabius. Currently, eight species of Edrabius are known from southern Peru, Argentina, and Chile. These are: E. alticolus Seevers; E. argentinus Seevers; E. chilensis Scheerpeltz; E. kus- cheli Scheerpeltz; E. pearsoni Seevers; E. peruanus Seevers; E. philippianus Fauvel; and E. weiseri Seevers. Of the species of Edrabius currently recognized, most occur on species of Ctenomys (Rodentia: Cteno- myidae), the tuco-tucos. However, in this paper we also report their occurrence on two additional genera of rodents, Aconae- mys and Octodon (Octodontidae). Cteno- myids and octodontids are caviomorph ro- dents that are found throughout southern South America. They occur in Argentina, Chile, southern Bolivia, and Peru and range in elevation from sea level to 4700 m (Mares & Ojeda 1982). Little information is available about the life history or habits of the species of Ed- rabius, or about the nature of the beetle- mammal interaction. Fauvel (1900) report- ed the observations of Philippi that adults and larvae of Edrabius philippianus were found around the anus of a species of Cten- omys and caused damage to the skin. Fau- vel received adult beetles that he subse- quently described, but he did not mention the larvae in his description, and he may not have actually received them. There have been no subsequent reports of amblyopi- nine larvae on any host, although hundreds of mammals carrying adult amblyopinines have been examined. Timm & Ashe (1989) described larval Edrabius that were found in the nest of Ctenomys in Chile. In this paper we: describe three new spe- cies of Edrabius; review previously pub- lished information about Edrabius; and pro- vide new information on host and geo- graphic distributions of Edrabius. Materials and Methods Recent field work in Chile by one of us (MHG) as part of his ongoing research on the systematics and biogeography of Cten- VOLUME 109, NUMBER 4 733 omys, as well as that of other field workers provide significant new information about, and specimens of, Edrabius. The new ma- terial prompted us to review the systematic status of all the species of Edrabius in Ar- gentina, Bolivia, Chile, and Peru. In the course of this study, we examined the types and dissected aedeagi of all de- scribed species of Edrabius except E. phi- lippianus. According to Seevers (1955) the holotype, and only known specimen, of E. philippianus is a female. He gives a de- tailed description of this specimen, includ- ing illustrations of distinctive pronotal fea- tures. None of the species described here match the description of E. philippianus given by Seevers. We also examined the specimens that Scheerpeltz (1957) identi- fied as E. philippianus and that he used in his comparisons with other species. We are convinced that these specimens are incor- rectly identified. They do not have the dis- tinctive pronotal shape that Seevers (1955) described for E. philippianus, and other de- scribed features also do not fit Scheerpeltz 's specimens very well (though these are more qualitative and less distinctive). In addition, all of Scheerpeltz's specimens are from Ar- gentina, whereas the type of E. philippianus is from Antofagasta, in the Atacama Desert of Chile. Specimens of Edrabius examined are de- posited in: Instituto de Ecologia y Evolu- cion, Universidad Austral de Chile, Valdi- via, Chile (lEEUACH); Field Museum of Natural History, Chicago, Illinois (FMNH); Snow Entomological Museum, University of Kansas, Lawrence (KSEM); and Natur- historisches Museum Wien, Vienna, Austria (NHMW). The mammal hosts are deposited in: Instituto de Ecologia y Evolucion, Univ- ersidad Austral de Chile, Valdivia, Chile (IEEUACH); American Museum of Natural History, New York (AMNH); Field Muse- um of Natural History (FMNH); Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico (MSB); Museum of Vertebrate Zoology, University of California, Berkeley, Califor- nia (MVZ). Edrabius grandis, new species Figs. 1-3 Description. — Length 9.0-10.5 mm. Uniformly light reddish-brown. Head shape variable, small males and females with lat- eral margins tapered uniformly from round- ed posterior angles to front, heads of larger males with lateral margins inflated and broadly rounded in posterior half (Fig. 1); integument of head with dense, prominent, small-meshed, isodiametric microsculpture, surface not strongly shining; without micro- punctures; microsetae on lateral margins behind eye very small and sparsely distrib- uted. Antenna (Fig. 2) longer than head and pronotum together, article 2 slightly longer than, or subequal to, article 3, article 4 slightly elongate; article 5 quadrate to slightly elongate; articles 6-10 slightly to moderately elongate. Pronotum (Fig. 1), moderately transverse, about 1.5-1.6 times as wide as long; without postero-lateral macroseta; microsetae on antero-lateral margins very small and sparsely distributed, microsetae extended from near middle of lateral margin of pronotum to antero-lateral angles and very sparsely along lateral third of anterior margin; integument with dense, prominent, small-meshed, isodiametric mi- crosculpture, sculpticells more prominent laterally than medially, surface not strongly shining (except in specimens in which the microsculpture has been eroded away due to abrasion); surface without micropunctu- res. Elytra with very fine, widely dispersed, golden-yellow microsetae, punctures very small. Abdomen uniformly covered with silky vestiture of moderately dense, very fine, yellowish microsetae. Male. — Posterior margin tergum VIII emarginate. Posterior margin of sternum VIII broadly and evenly emarginate, maxi- mum depth of emargination about 0.5 times width of emargination. Aedeagus. — As in Fig. 3. 734 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 1 Figs. 1-3. Edrabius grandis n. sp. L Head and prothorax, dorsal (scale = 1.0 mm); 2. Antenna (scale 1.0 mm); 3. Apex of aedeagus, lateral (scale = 0.1 mm). VOLUME 109, NUMBER 4 735 Holotype. — Male, with labels as follows: "Argentina: Prov. Rio Negro; 13 km WSW Comallo, el. 1150 m, 15 Nov 1987, A. K. and O. P. Pearson #OPP 7435, ex. Cteno- mys haigi (MVZ 175156)." "HOLOTYPE, Edrabius grandis Ashe, Timm, & Gallardo, Designated J. S. Ashe, R. M. Timm, and M. L. Gallardo 1995." Deposited in the Snow Entomological Museum, University of Kansas, Lawrence, Kansas. Paratypes. — 6, from the following local- ities. Argentina: Rio Negro Prov., 3-V- 1986, M. H. Gallardo #833, ex. Ctenomys haigi (lEEUACH 1535) 9, 2 males 2 fe- males. Same locality, date, and collector, MHG #837, ex. Ctenomys coyhaiquensis (IEEUACH 1539), 1 male. Chile: Coyh- aique Prov.; 4.5 km SE Coyhaique Alto, Fundo Los Flamencos, 750 m; M. H. Gal- lardo #1092, ex. Ctenomys coyhaiquensis 6 (IEEUACH 4233), 1 male. Paratypes de- posited in IEEUACH and KSEM. Distribution. — Known from the Rio Ne- gro Valley in Argentina and adjacent Coyh- aique in Chile. Hosts. — Collected from Ctenomys coy- haiquensis in Coyhaique, Chile, and C. hai- gi in Rio Negro Province, Argentina. Discussion. — Specimens of this species are among the largest of any described spe- cies of Edrabius. They can be recognized by: large size; relatively elongate antenna with elongate antennomeres; head and pro- notum densely reticulate with isodiametric sculpticells; integument of head and pro- notum without micropunctures; microsetae on lateral margins of head and pronotum very small and sparsely distributed; and, the distinctive aedeagus. Edrabius australis, new species Figs. 4-6 Description. — Length 7.0-9.0 mm. Uni- formly light reddish-brown. Head shape (Fig. 4) with lateral margins uniformly ta- pered from rounded posterior angles ante- riorly; integument of head with faint, iso- diametric microsculpture, microsculpture obsolete to absent postero-medially, sur- face strongly shining; micropunctures ex- tremely fine and inconspicuous; microsetae on lateral margins of head behind eye sparse to moderate in size and number. An- tenna (Fig. 5) longer than head and pro- thorax together; article 2 slightly shorter than, to subequal to, length of article 3, article 4 quadrate to slightly elongate, ar- ticles 5-10 quadrate to slightly elongate. Pronotum (Fig. 4) moderately transverse, about 1.4-1.5 times as wide as long; with- out postero-lateral macroseta; microsetae on antero-lateral border variable from sparse and located in antero-lateral half, to moderately dense and extended along lat- eral margin from near posterior third of pronotum to antero-lateral angles and along lateral third of anterior margin; in- tegument with faint microsculpture, sculp- ticells isodiametric laterally but slightly elongate medially, surface strongly shin- ing; micropunctures extremely fine and in- conspicuous. Elytra with moderate sized, uniformly distributed, yellowish microse- tae, punctures small. Abdomen uniformly covered with silky vestiture of moderately dense yellowish microsetae. Male. — Posterior margin of tergum VIII broadly and moderately emarginate. Poste- rior margin of sternum VIII broadly and deeply emarginate, emargination broadly rounded internally, width of emargination about 2.3 times depth. Aedeagus. — As in Fig. 6. Holotype. — Male, with labels as follows: "Chile: Bio-Bio Prov.; Laguna Laja, 21-III- 1987, M. H. Gallardo 1011 & 1012, ex. Ctenomys maulinus maulinus (lEEUACH 1640 & 1641)." "HOLOTYPE, Edrabius australis Ashe, Timm, & Gallardo, Desig- nated J. S. Ashe, R. M. Timm, and M. H. Gallardo 1995." Deposited in Zoological Collections of the Universidad Austral de Chile, Valdivia, Chile. Paratypes. — 12, same data as holotype; 11, Chile: same locality, date, and collector, MHG #1017, ex. Ctenomys maulinus mau- 736 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Figs. 4-6. Edrabius australis n. sp. 4. Head and prothorax, dorsal (scale 1.0 mm); 6. Apex of aedeagus, lateral (scale = 0.1 mm). 1.0 mm); 5. Antenna (scale = linus (lEEUACH 1646). Paratypes depos- ited in ffiEUACH and KSEM. Distribution. — Known only from Petron- quines, Laguna Laja, Bio-Bio Province, Chile. Host. — Collected only from Ctenomys maulinus maulinus. Discussion. — This species can be distin- guished by the relatively faint reticulation of the head and prothorax with extremely VOLUME 109, NUMBER 4 737 Figs. 7-9. Edrabius chilensiformis n. sp. 7. Head and prothorax, dorsal (scale =1.0 mm); 8. Antenna (scale 1.0 mm); 9. Apex of aedeagus, lateral (scale = 0.1 mm). fine and inconspicuous micropunctures, and and tapered from broadly-rounded posterior the distinctive aedeagus. Edrabius chilensiformis, new species Figs. 7-9 Description. — Length 5.0-6.0 mm. Red- angles to anterior margins; integument with moderate, elongate, irregularly wavy mi- crosculpture, sculpticells obsolete to absent medially, integument strongly shining; mi- cropunctures numerous, very minute; mi- dish-brown. Head shape (Fig. 7) rounded crosetae on lateral margins behind eye 738 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON moderately dense. Antenna (Fig. 8) about as long as head and pronotum together; ar- ticle 2 subequal in length to article 3, arti- cles 4-10 quadrate to subquadrate. Prono- tum (Fig. 7) moderately transverse, about 1.4 times as wide as long; with postero-lat- eral macroseta; microsetae on antero-lateral margin prominent and more or less densely distributed in anterior half of lateral mar- gins and along anterior third of anterior margins, integument with faint, irregular wavy microsculpture, sculpticells obsolete to absent medially, surface strongly shining; micropunctures numerous, very minute. El- ytra with moderately dense, yellowish mi- crosetae, punctures moderate in size. Ab- domen uniformly covered with silky vesti- ture of very densely distributed, yellowish microsetae. Male. — Posterior margin of tergum VIII very shallowly and broadly emarginate. Posterior margin of sternum VIII broadly and deeply emarginate, emargination broad- ly rounded; width of emargination about 2.0 times depth. Aedeagus. — As in Fig. 9. Holotype. — male, with labels as follows: "Chile: Coquimbo Prov.; 10 km N Puente Los Molles, 32°09'S, 71°3rw, 26-VII- 1976, R. E. Martin #1470, ex. Octodon de- gus 9 (FMNH 119659)." "HOLOTYPE, Edrabius chilensiformis Ashe, Timm, & Gallardo, Designated J. S. Ashe, R. M. Timm, and M. L. Gallardo 1995." Depos- ited in the Field Museum of Natural His- tory, Chicago, Illinois. Paratypes. — 3, same data as holotype. Paratypes deposited in FMNH and KSEM. Distribution. — Known only from Co- quimbo Province, Chile. Host. — Collected from Octodon degus (Octodontidae). Discussion. — This species is closely re- lated to Edrabius chilensis Scheerpeltz from which it can be distinguished by the denser abdominal setation and distinctive aedeagus of E. chilensiformis. Edrabius chilensis and E. chilensiformis appear to form a distinctive monophyletic group within Edrabius characterized by the syna- pomorphous condition of an upturned and apically pointed aedeagus (see Fig. 9, and fig. 2C in Scheerpeltz 1957). In contrast, these two species appear to retain several plesiomorphic characteristics not found among other known Edrabius. These ap- parent plesiomorphies include: presence of a postero-lateral seta on the pronotum (also found among many free-living quediines, as well as the amblyopinines — Amblyopino- des, Amblyopinus, Megamblyopinus, and Myotyphlus, but not present on other known Edrabius), and the very weakly developed cluster of long aciculate setae on the apex of the lateral plates of abdominal segment 9 (very strongly developed among other known Edrabius — see Seevers 1955, fig. 44G). This suggests that these two species occupy a relatively basal position in the phylogeny of Edrabius. It is also interesting that both of these species are known from caviomorph ro- dents other than Ctenomys in the family Oc- todontidae: Edrabius chilensis from the rock rat, Aconaemys fuscus and E. chilen- siformis from the degu, Octodon degus. In contrast, most other Edrabius are known from Ctenomys (the only exception is E. kuscheli from the nest of a cui. Galea mus- teloides (Caviidae), but see below). New Records Edrabius alticolus Seevers. Bolivia: Dept. Oruro; 3.5 km E Huancaroma, 6-VIII-1984, ex. Ctenomys opimus opimus 9, NK 11550 (MSB 55377), 1 male. Oruro; 2.5 km NE Huancaroma, 3720 m, 6-VIII- 1984, ex. Ctenomys opimus opimus 9, NK 11566 (AMNH 260837), 2 males. Oruro; 1 km N, 5 km W Pomata Ayte, Rio Barros, 11 -IX- 1986, ex. Ctenomys opimus opimus S, NK 14549 (AMNH 263040), 1 male 1 female. Oruro; Huancaroma, 2-X-1986, ex. Ctenomys opimus opimus 9, NK 14765 (MSB 57197), 2 males. Chile: Parinacota Prov.; D. Reise #2710, ex. Ctenomys opi- VOLUME 109, NUMBER 4 739 mus (lEEUACH 4332), 2 males 2 females (KSEM and lEEUACH). Edrabius argentinus Seevers. Argentina: Mendoza Pro v.; 5.7 km NW Villavicencio, 2800 m, 31 December 1981, Richard D. Sage #10656, ex. Ctenomys haigi (MVZ 162936), 1 male (KSEM). Seevers (1955: 258) described E. argentinus from "ex nido de Ctenomys" from Argentina: Catamarca; Hualfin (near Tucuman). On the basis of the locality, we believe the host to be Ctenomys tucumanus. Notes. — This specimen differs from the type series of Edrabius argentinus in hav- ing a slightly longer antenna with longer articles 4-10, more uniformly rounded lat- eral margins of the pronotum and mostly isodiametric microsculpture on pronotum (more wavy on specimens in type series). However, the aedeagus is highly distinctive and cannot be distinguished from the ae- deagus of the holotype of E. argentinus. Therefore, we have chosen to assign the specimen from Mendoza Province to E. ar- gentinus in spite of the minor differences noted above. It is possible that a new sub- species should be established for the Men- doza population; however, until more spec- imens of E. argentinus are known from the original population, the Mendoza Province population, and other intervening popula- tions, it would be premature to describe such a subspecies. Edrabius chilensis Scheerpeltz. Chile: Cautin Prov.; Quetropillan; P. Mondaca #439, ex. Aconaemys porteri (lEEUACH 4119), 1 male 1 female. Malleco Prov.; Parque Nacional Nahuelbuta, 10-1-1976, Robert E. Martin #1339, ex. Aconaemys fuscus, 1 male (lEEUACH and KSEM). Notes. — The specimen from Malleco Province has an aedeagus that is slightly more robust apically than that of the spec- imens from Cautin and that shown in Scheerpeltz's (1957) figure. However, this slight difference does not seem sufficient to assign this specimen to a new species. Edrabius peruanus Seevers. Chile: Pari- nacota Prov.; ex. Ctenomys opimus, 3 males 4 females (lEEUACH and KSEM). Edrabius philippianus Fauvel. Fauvel (1900) described E. philippianus from Ctenomys sp. from Antofagasta, Chile. We herein correct the type host identification to be C. fulvus as that is the only species of tuco-tuco occurring in Antofagasta (Gallar- do 1991). Edrabius weiseri Seevers. Bolivia: Dept. Oruro; 7 km S, 4 km E Cruce Ventilla, 3450 m, 30-IX-1986, ex. Ctenomys opimus opi- mus ?, NK 14748 (MSB 57194), 1 male. Dept. Potosi; 2 km E ENDE Camp, Laguna Colorado, 4280 m, 16-IX-1986, ex. Cteno- mys opimus opimus 9, NK 14571 (AMNH 263051), 1 male. Potosi; 2 km E ENDE Camp, Laguna Colorado, 4278 m, 16-IX- 1986, ex. Ctenomys opimus opimus 9, NK 14572 (MSB 57204), 7 males 20 females (KSEM). Discussion Two major groups of Edrabius are ap- parent. One, represented by E. chilensis and E. chilensiformis, is found on Aconaemys and Octodon respectively, both in the fam- ily Octodontidae (Table 1). These two small species of Edrabius share the synapomor- phy of a sharply pointed and upturned apex to the aedeagus. However, they share a number of plesiomorphic features not found in other Edrabius (see discussion under E. chilensiformis) . The second major Edrabius lineage is made up of those species that have the apo- morphic conditions of the following char- acteristics: that is, pronotum without a pos- tero-lateral macroseta, and a very distinct and prominent "pencil" of aciculate setae on the apices of the lateral styli of abdom- inal tergum IX. This lineage includes all the other known species of Edrabius. Members of this second lineage are found primarily on various species of the genus Ctenomys, the sole genus in the family Ctenomyidae, though all known specimens of E. kuscheli 740 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASfflNGTON Table 1 . — Summary of known general distribution and hosts of Edrabius species (Staphylinidae, Amblyopi- nini). General distribution E. alticolus Seevers Peru: Tacna Prov. Bolivia: Oruro Prov. Chile: Parinacota E. argentinus Seevers Argentina: Catamarca Argentina: Mendoza Prov. E. australis Ashe, Timm, & Gallardo Chile: Bio-Bio Prov. Ctenomys fulvus Ctenomys opimus Ctenomys opimus "nest of Ctenomys'" [Ctenomys tucumanus] Ctenomys mendocinus Ctenomys maulinus maulinus E. chilensiformis Ashe, Timm, & Gallardo Chile: Coquimbo Prov. E. chilensis Scheerpeltz Chile: Curico Chile: Malleco Prov. Chile: Cautin Prov. E. grandis Ashe, Timm, & Gallardo Argentina: Rio Negro Prov. Chile: Coyhaique Prov. E. kuscheli Scheerpeltz Chile: Arica-Lipiche E. pearsoni Seevers Peru: Puno Prov. E. peruanus Seevers Peru: Puno Prov. Chile: Parinacota Prov. E. philippianus Fauvel Chile: Antofagasta E. weiseri Seevers Argentina: Jujuy Bolivia: Dept. Oruro Bolivia: Dept. Potosi Octodon degus "An Ratten" Aconaemys fuscus Aconaemys porteri Ctenomys haigi Ctenomys coyhaiquensis ' 'nest of Galea musteloides' ' Ctenomys opimus nigriceps Ctenomys peruanus Ctenomys opimus Ctenomys fulvus host unknown Ctenomys opimus opimus Ctenomys opimus opimus Seevers, 1955 this paper this paper Seevers, 1955 this paper this paper this paper Scheerpeltz, 1957 this paper this paper this paper this paper Scheerpeltz, 1957 Seevers, 1955 Seevers, 1955 this paper Seevers, 1955 Seevers, 1955 this paper this paper were found in the nest of a cui. Galea mus- teloides (but see below) (Table 1). Scheerpeltz (1957), illustrated specimens of Edrabius kuscheli, E. philippianus, and E. chilensis showing a posterolateral seta on the pronotum. However, our examination of the holotype of E. chilensis, all paratypes of E. kuscheli, and specimens labeled E. philippianus (almost certainly misidenti- fied, see above) from Scheerpeltz's collec- tion clearly show that specimens of both species lack posterolateral pronotal setae. whereas all three specimens of the type se- ries of E. chilensis have such setae. Furthermore, Seevers (1955), in a quote from O. P. Pearson (page 254), notes that Galea musteloides frequently use old Cten- omys burrows. If true, then movement of individuals of Galea into Ctenomys bur- rows that already had a population of Ed- rabius could account for this unusual host record. Members of the genus Ctenomys, the tuco-tucos, are small to mid-sized (100- VOLUME 109, NUMBER 4 741 1500 g), strictly fossorial rodents forming a complex assemblage of species with fairly uniform morphology, but extremely vari- able in chromosome number (Gallardo 1991, Reig et al. 1990). The genetic varia- tion found in the family Ctenomyidae is nearly as great as is found in all other mam- mals (Gallardo & Kohler 1992, Gallardo & Palma 1992). Although there are 56 avail- able species names of Ctenomys, the num- ber of valid species recognized by recent authors ranges from 32 to 44 (Kelt & Gal- lardo 1994, Mares & Ojeda 1982, Nowak 1991, Reig et al. 1990, Woods 1993). There is consensus that the genus is in need of revision. Tuco-tucos, being strictly fossori- al, subterranean dwellers, are restricted to particular soil types and are poor at long distance dispersal and dispersal over water, as is true for other groups of fossorial ro- dents occupying grasslands on other conti- nents (i.e., the pocket gophers of North America (Geomyidae); the African mole- rats (Bathyergidae); and the mole-rats of Eurasia (Spalacidae)). The subterranean ecotype limits dispersal and produces a population structure characterized by demic fragmentation that facilitates extensive chromosomal variation (Gallardo 1991). In the few species of tuco-tucos studied to date, all maintain extensive underground tunnel systems and have a well-formed, grass-lined nest chamber (Gallardo & An- rique 1991). Reig et al. (1990) suggested that the extensive distribution of tuco-tucos in the southern cone of South America and the lack of morphological differentiation, suggested that the major radiation of the ge- nus was almost certainly post-Pleistocene, although the geologic age of the family goes back to the Pliocene; however, given the diversity, the time of divergence must certainly have been longer. The ctenomyids are believed to be the sister group to the Octodontidae, and it has been suggested that they are more properly classified as a subfamily of the Octodontidae (Reig et al. 1990). The caviomorph family Octodontidae contains six genera and 1 1 living species, all with very restricted Andean or pre-An- dean ranges. Their habits are diverse. Oc- todon degus is similar to a ground squirrel in behavior, diet, and ecology. Aconaemys fuscus is fossorial and similar in size and shape to Ctenomys, though less specialized for burrowing (Gallardo & Reise 1992). Other octodontids (Octomys) have habits that are similar to woodrats or are strictly fossorial (Spalacopus). The biology, ecol- ogy, and geographical distributions of most species of octodontids are very poorly known and phylogenetic relationships among the genera are uncertain (Mares & Ojeda 1982, Nowak 1991). Contreras et al. (1987) discussed known aspects of the ecol- ogy, distribution, and biogeography of the Octodontidae. Reig et al. (1990) note that the families Ctenomyidae and Octodontidae (they treat- ed these taxa as subfamilies rather than families) are sister taxa. The Octodontidae are known from the Oligocene of Argentina (Mares & Ojeda 1982, Nowak 1991, Con- treras et al. 1987), and it seems possible that the association of Edrabius with this lin- eage of caviomorph rodents may date to at least this time period. The relatively recent differentiation of Ctenomys (Reig et al. 1990) is reflected in evolution of the Edrabius found on Cteno- mys into a number of poorly differentiated species. It is virtually impossible to separate the species of Edrabius based exclusively on external characteristics. Aedeagal char- acteristics are more distinctive, but some (£". peruanus, E. pearsoni, and E. alticolus) are also only weakly differentiated by ae- deagal features. A clear understanding of patterns of species limits and geographic variation of Edrabius species associated with Ctenomys will require much more ex- tensive collecting. Few other amblyopinines are known from caviomorph rodents. The only two known species of Megamblyopinus are found on Ctenomys — M. germaini Fauvel on C. peruanus Sandbom & Pearson and 742 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON M. mniszechi on C opimus nigriceps Tho- mas. In addition, Amblyopinus fuegensis Seevers occurs on Ctenomys magellanicus, A. pacae Seevers is known from Agouti tac- zanowskii, and Amblyopinodes caviae Mar- tinez & Prosen is known from Cavia spe- cies (Caviidae) (Seevers 1955, Machado- Allison 1963). Given the extensive radiation of Cteno- mys in southern South America and the rel- atively few collections of Edrabius from these rodents, we strongly suspect that nu- merous new species of Edrabius remain to be collected. In addition, other species of Edrabius may be associated with other gen- era of the Octodontidae. Because of the rel- atively basal phylogenetic position of those Edrabius currently known to be associated with octodontids, it is likely that additional collections of Edrabius from octodontids will prove pivotal to understanding the phy- logeny and evolution of association of Ed- rabius with caviomorph rodents. Acknowledgments We especially thank the following col- leagues for their efforts in collecting am- blyopinine staphylinid beetles and for mak- ing the specimens and their associated data available for our study: William L. Gannon, Donald Gettinger, Douglas A. Kelt, Robert E. Martin, Anita K. and Oliver P. Pearson, Richard D. Sage, Barbara R. Stein, and Ter- ry L. Yates. The following museums and curators loaned specimens in their care for our study: Naturhistorisches Museum Wien, Vienna, Austria; Field Museum of Natural History, Chicago (A. F. Newton, Jr.) (FMNH). Jim Pakaluk reviewed the manu- script and provided many constructive com- ments. M. Gallardo's field work was funded in part by Fondo Nacional de Ciencias, Grant 92-0178 and DID UACH, Grant S-94-29. This research was also funded in part by University of Kansas General Re- search Fund Grant 3953-20-0038 to J. S. Ashe. Contribution number 3131 from the Snow Entomological Museum. Literature Cited Ashe, J. S., & R. M. 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