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Containing group: Cerylonid Series

Introduction

Latridiidae, whose members are more commonly known as the Minute Brown Scavenger Beetles, is a family of very small (1-3 mm) mycophagous and myxomycophagous beetles.  At present, the family includes 35 genera and approximately 1100 species (including fossil taxa).  Latridiidae is divided into 3 subfamilies (2 extant and 1 extinct):  Latridiinae, Corticariinae and Tetrameropsinae.  Although latridiids are best known from the temperate regions of the world, the family is truly cosmopolitan with several genera widely introduced as stored product pests (e.g., Corticaria, Melanophthalma, Latridius).

Most latridiid adults and larvae feed on the conidia and hyphae of phycomycete, deuteromycete and ascomycete fungi, while a small number of species are specialists on myxomycete spores (Lawrence 1982, Lawrence 1991, Andrews 2002, Hartley and McHugh in press).  Adults are most often encountered during the wetter seasons of the year and are frequently collected by beating decaying vegetation and by Berlese funnel extraction from sifted leaf litter.  They are also occasionally collected in pitfall traps and light traps.  Some species are known to be associated with the litter in nests of Neotoma wood rats (Hartley et al. 2007, Hartley and McHugh in press).  At least 30 widespread species have been listed as stored product pests of humans (Hinton 1941), and one species, Eufallia seminiveus Motschulsky was reported to bite humans (Parsons 1969).

Characteristics

In general, adults of the family are fairly small in size and cryptically colored (brown to black) with an elongate to elongate-oval body shape.  The adult forms of each extant subfamily are very distinct from one another, allowing for easy identification.  Latridiidae exhibits interesting anatomical diversity, with some members exhibiting aptery or brachyptery, reduction or complete loss of eyes, elongate cylindrical trochanters and fused elytra.  In general, the adults can be characterized by the combination of the following features (based on Lawrence et al. 1999a, Andrews 2002, Lord 2008, Hartley and McHugh in press): 

• Small size, ranging from 1-3 mm
• Elongate to elongate-oval habitus
• Antennae 10 or 11-segmented with a 2-3 segmented apical club, inserted on frons between eyes
• Tarsi 3-3-3, simple, linear (occasionally bearing a ventral lobe on tarsomere I), claws simple (appendiculate in Rethusus)
• Body surface glabrous (Latridiinae) or pubescent (Corticariinae)
• Dorsal surfaces rugosely sculptured with dorsal carinae (Latridiinae) or not rugose (Corticariinae)
• Partially to heavily covered by waxy exudates (Latridiinae) or lacking these exudates entirely (Corticariinae).

Very few latridiid species have described larvae.  The taxa for which the immature stages are known show significant variability in form, sculpture, and vestiture.  Larvae range in size from 1-3 mm and are elongate and subcylindrical in form.  The body is generally white in color, often with a darker head (occasionally with darker protergal maculae).  The vestiture generally includes scattered long, simple setae, occasionally mixed with apically-frayed setae.  Latridiid larvae can be distinguished from other similar larvae by combination of the following characters (based on Lawrence 1991, Lawrence et al. 1999a, Hartley and McHugh in press): 

• Head with epicranial stem short to moderately long (may be absent in some), frontal arms usually V-shaped
• Frontoclypeal suture absent
• 1-5 pairs of stemmata (usually 3 or 4), occasionally absent
• Antennae 3-segmented, usually with antennomere II 1.5X length of antennomere III and 3X length of antennomere I, occasionally with antennomeres II and III subequal and each twice as long as antennomere I
• Mandibles symmetrical, unidentate to quadridentate, mola well-developed and tuberculate or aspirate, usually with a well-developed broadly rounded or acute hyaline prostheca
• Legs well-developed, 5-segmented with unisetose tarsungulus
• Lacking urogomphi
• Spiracles annular
  

Taxonomy

Although Corticariidae Curtis, 1829, has priority over Latridiidae Erichson, 1842 (Lawrence and Newton 1995), we have elected to use the more commonly used junior synonym.  Many modern workers have argued for conservation of Latridiidae as the name of the family based on familiarity and to promote nomenclatural stability.  To date, no one has assembled a proposal to the International Commission of Zoological Nomenclature for a formal ruling on this issue.

Previous taxonomic authorities included four tribes within Latridiidae:  Latridiini, Corticariini, Merophysiini and Dasycerini.  Crowson (1955) removed Merophysiini and Dasycerini from Latridiidae, elevated both to the family-level, and elevated the remaining two tribes (Latridiini and Corticariini) to the subfamilial-level.  Subsequent workers placed Merophysiidae and Dasyceridae as subfamilies within other families, Endomychidae and Staphylinidae, respectively. 

Despite the existence of several significant generic-level treatments (Belon 1902, Hetschko 1926), a lack of family-level revisions has left generic definitions relatively unstable.  Over the intervening 75 years since these catalogues were published, descriptions of many new taxa, most as isolated single-species treatments has led to underestimation of the diversity of the group.  Likewise, persistent confusion at the species-level continues to plague many heterogenous genera within the family.  In recent years, renewed interest in latridiid systematics (e.g., Hartley et al. 2007, Johnson 2007, Lord 2008, Hartley and McHugh in press) has contributed to the resolution of some of these classification issues.

Discussion of Phylogenetic Relationships

Previous workers have argued that Latridiidae, although lacking strong synapomorphies, appears to be a natural group and may be the sister group of Corylophidae (Ślipiński and Pakaluk 1991).  However, very few phylogenetic analyses have been conducted that include sufficient taxa to test the monophyly of the group or its constituent subfamilies.  Recent phylogenies of higher order taxa based on molecular sequence data and including exemplar latridiid taxa have only raised questions about the monophyly of the family.

The first formal phylogenetic analysis to include latridiids was that proposed from the Bayesian analysis of 18S, 16S and COI gene sequences by Hunt et al. (2007).  Although the latridiid sampling was very limited in that study, Latridiidae and both subfamilies were recovered as monophyletic.  A later study focusing on the relationships of the families and subfamilies of the Cerylonid Series by Robertson et al. (2008) recovered Latridiidae and both subfamilies as monophyletic based on Bayesian analysis of 18S and 28S.  Interestingly, Latridiidae was recovered as paraphyletic with respect to Discolomatidae, Corylophidae and Anamorphinae (Endomychidae) using both maximum parsimony and POY analysis, but Latridiinae and Corticariinae were both supported as monophyletic in all analyses.  To date, there are no phylogenetic analyses based on morphology for Latridiidae, leaving the relationship of the extinct subfamily Tetrameropsinae to the remaining extant subfamilies unresolved.

Other Names for Latridiidae

• Lathridiidae
• Corticariidae Curtis, 1829
• Minute brown scavenger beetles

References

Andrews, F.G. 2002. Chapter 95. Latridiidae Erichson 1842, pp. 395-398. In R. H. Arnett, M. C. Thomas, P. E. Skelley and J. H. Frank [eds.], American Beetles, Volume 2. CRC Press, Boca Raton, FL.

Belon, R. P. 1902. Coleoptera Clavicornia Fam. Lathridiidae, pp. 1-40 + 1 pl. In P. Wytsman [ed.], Genera Insectorum. P. Wytsman, Brussels.

Crowson, R.A. 1955. The Natural Classification of the Families of Coleoptera. Lloyd, London. 187 pp.

Hartley, C. and J.V. McHugh. 10.35. Latridiidae Erichson, 1842. In R.G. Beutel and R.A.B. Leschen (eds.). Handbuch der Zoologie. Band IV, Teilband 38, vol. 2. De Gruyter, Berlin. In Press.

Hartley, C., F.G. Andrews and J.V. McHugh. 2007. A revision of Akalyptoischion (Coleoptera: Cucujoidea). Patricia Vaurie Monograph Series Monograph 6. Coleopterists Society, North Potomac, MD. 50 p.

Hetschko, A. 1926. Pars 85: Lathridiidae. In S. Schenkling [ed.], Coleopterorum Catalogus. W. Junk, Berlin. 86 p.

Hinton, H.E. 1941. The Lathridiidae of economic importance. Bulletin of Entomological Research 32: 191-247.

Hunt, T., J. Bergsten, Z. Levkanicova, A. Papadopoulou, O. St. John, R. Wild, P. M. Hammond, D. Ahrens, M. Balke, M. S. Caterino, J. Gomez-Zurita, I. Ribera, T. G. Barraclough, M. Bocakova, L. Bocak, and A. P. Vogler. 2007. A comprehensive phylogeny of beetles reveals the evolutionary origins of a superradiation. Science 318: 1913-1916.

Johnson, C. 2007. Family Latridiidae Erichson, 1842, pp. 635-648. In I. Lobl and A. Smetana [eds.], Catalogue of Palaearctic Coleoptera. Volume 4. Elateroidea - Derodontoidea - Bostrichoidea - Lymexyloidea - Cleroidea - Cucujoidea. Apollo Books, Stenstrup. 935 p.

Lawrence, J. F. 1982. Lathridiidae, pp. 533-534. In S. P. Parker [ed.], Synopsis & Classification of Living Organisms. McGraw Hill, Inc., New York.

Lawrence, J. F. 1991. Lathridiidae (Cucujoidea), pp. 497-498. In F. W. Stehr [ed.], Immature Insects. Volume 2. Kendall/Hunt Publishing Company, Dubuque, IA.

Lawrence, J. F., A. M. Hastings, M. J. Dallwitz, T. A. Paine, and E. J. Zurcher 1999a. Beetles of the World: A Key and Information System for Families and Subfamilies. CD-ROM, version 1.0 for MS-Windows. CSIRO Publishing, Melbourne.

Lawrence, J. F., A. M. Hastings, M. J. Dallwitz, T. A. Paine, and E. J. Zurcher 1999b. Beetle Larvae of the World: Descriptions, Illustrations, Identification, and Information Retrieval for Families and Sub-families. CD-ROM, version 1.1 for MS-Windows. CSIRO Publishing, Melbourne.

Lawrence, J. F., and A. F. Newton. 1995. Families and subfamilies of Coleoptera (with selected genera, notes, references and data on family-group names), pp. 779-1006. In J. Pakaluk and S. A. Slipinski [eds.], Biology, Phylogeny, and Classification of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Museum i Instytut Zoologii PAN, Warszawa.

Lord, N.P. 2008. Systematics within the Cerylonid Series (Coleoptera: Cucujoidea). Masters Thesis, University of Georgia, Athens. [unpublished]

Pakaluk, J., S. A. Slipinski, and J. F. Lawrence. 1994. Current classification and family-group names in Cucujoidea (Coleoptera). Genus 5: 223-268.

Parsons, C. T. 1969. A lathridiid beetle reported to bite man. The Coleopterists Bulletin 23: 15.

Robertson, J.A., M.F. Whiting and J.V. McHugh. 2008. Searching for natural lineages within the Cerylonid Series (Coleoptera: Cucujoidea). Molecular Phylogenetics and Evolution 46 (1): 193-205.

Ślipiński, S. A., and J. Pakaluk. 1991. Problems in the classification of the Cerylonid series of Cucujoidea (Coleoptera), pp. 79-88. In M. Zunino, X. Belles and M. Blas [eds.], Advances in Coleopterology. AEC, Barcelona.

Information on the Internet

• Fauna Europaea – Latridiidae.
• Latridiidae on Wikispecies.
• Wolfgang Rücker – Latridiidae & Merophysiinae.