Lutrochus

Introduction

Lutrochidae is one of the smaller beetle families with only 11 species described in the one genus Lutrochus (Shepard 2002). However, Lutrochus will likely be split, and many other species and 2-3 additional genera await description. So far, all lutrochids occur only in the New World, from the USA south at least to Paraguay (Shepard and Julio 2010).

All lutrochids are stream-associated.  One group of species is often found in bankside vegetation hanging into or over the water or in leaf packs that accumulate on sticks and rocks. A second group of species occurs where artesian waters enter streams and travertine deposits form on submerged wood and vegetation. Larvae of this group mine the travertine consuming the organic matter. The common name for the family comes from this group of species.

Known life cycles are univoltine. Oviposition is into wet organic matter. Larvae undergo several stadia and then pupate under objects just above the water level. Adults are found close to the larvae. Adults and larvae feed on algae and waterlogged organic matter. Life cycle information is available for L. arizonicus (Brown and Murvosh 1970) and L. germari (Costa et al. 1996).

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Lutrochus. © Alex Wild

Characteristics

Adult and larval morphologies have been well described (Hinton 1939; Brown and Murvosh 1970; Brown 1991; Costa et al. 1996).  Identification keys exist for North American species (Brown 1972) and most South American species (Grouvelle 1896) (in French).

Adults can be recognized by the following characters:

• Short, thick body
• Pubescence a dense, golden hydrofuge or erect black setae
• Antennae short, first two antennomeres long and broad
• Stream-associated

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Lutrochus vestitus, larva © Susan McCormick

Larvae can be recognized by the following characters:

• Body short, cylindrical and well-sclerotized
• Head large and robust
• Pleurites on four or less abdominal segments
• Terminal, ventral abdominal operculum concealing retractile tracheal gills and two stout hooks.
• Apex of abdomen broadly rounded
• Stream-associated

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Lutrochus luteus, larva © Susan McCormick

Classification

Lutrochids were first placed in Dryopidae. Then Hinton (1939) moved them into Limnichidae where they remained until given their own family status (Kasap and Crowson 1975).

 Identification keys exist for North American species (Brown 1972) and most South American species (Grouvelle 1896) (in French).

Relationships of Lutrochidae to Other Beetles

Phylogenetic analyses of morphological data have put Lutrochidae as a sister group to Dryopidae (Lawrence 1987), to (Elmidae + Psephenidae) (Beutel 1995) or to (Limnichidae + Dryopidae + Heteroceridae) (Costa et al. 1999).

Other Names for Lutrochus

• Lutrochidae Kasap & Crowson
• Travertine beetles

References

Beutel, R. G. 1995. Phylogenetic analysis of Elateriformia (Coleoptera: Polyphaga) based on larval characters. Journal of Zoological Systematics and Evolutionary Research, 33(4): 145-171.

Brown, H. P. 1972. Aquatic Dryopoid Beetles (Coleoptera) of the United States. U. S. Environmental Protection Agency. Biota of Freshwater Ecosystems. Identification Manual No. 6. 82 pp.

Brown, H. P. 1991. Lutrochidae (Dryopoidea). Pages 397-399. In: F. W. Stehr (ed.). Immature Insects. Volume 2. Kendall/Hunt. Dubuque, Iowa. 975 pp.

Brown, H. P. and C. Murvosh. 1970. Lutrochus arizonicus new species, with notes on ecology and behavior (Coleoptera, Dryopoidea, Limnichidae). Annals of the Entomological Society of America, 63(4): 1030-1035.

Costa, C., I. Serfio, S. A. Vanin and É. P. Teixeira. 1996. Larvae of Neotropical Coleoptera. XXIII: Lutrochus germari Grouvelle, description of immatures, redescription of adult and bionomics (Dryopoidea, Lutrochidae). Revista Brasileira de Entomologia, 40(1): 47-56.

Costa, C., S. A. Vanin and S. Ide. 1999. Systematics and bionomics of Cneoglossidae with a cladistic analysis of Byrrhoidea sensu Lawrence & Newton (1995) (Coleoptera, Elateriformia). Arqivos de Zoologia, 35(3): 231-300.

Grouvelle, A. 1896. Description de deux Dryopides du genre Lutrochus Er. Avec tableau general des espèces [Col.]. Bulletin de la Société de France, 1-2: 16-17.

Hinton, H. E. 1939. An inquiry into the natural classification of the Dryopoidea, based partly on a study of their internal anatomy (Col.). Transactions of the Royal Entomological Society of London, 89(7): 133-184.

Ide, S., C. Costa and S. A. Vanin. 2005. 18.4. Lutrochidae Kasap & Crowson, 1975. Pages 508-512. In: R. G. Beutel and R. A. B. Leschen (eds.). Handbook of Zoology. Volume IV. Arthropoda: Insecta. Coleoptera, Beetles. Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim). Walter de Gruyter. Berlin. 567 pp.

Lawrence, J. F. 1987. Rhinorhipidae, a new beetle family from Australia, with comments on the phylogeny of the Elateriformia. Invertebrate Taxonomy, 2: 1-53.

Shepard, W. D. 2002. Chapter 45. LUTROCHIDAE Kasap and Crowson 1975. Pages 123-124. In: Arnett, R. H., M. C. Thomas, P. E. Skelley and J. H. Frank (eds.). American Beetles. Volume 2. CRC Press. Boca Raton, Florida. 861 pp.

Shepard, W. D. and C. A. Julio. 2010. Estudio preliminary de las familias de escarabajos acuáticos Dryopidae, Elmidae, Lutrochidae y Psephenidae conocidos de Paraguay (Coleoptera: Byrrhoidea). Boletin del Museo Nacional de Historia Natural de Paraguay, 16(1): 30-42.

Information on the Internet

• Lutrochidae page at bugguide.net