Silphinae

Based on maximum likelihood tree from Dobler & Müller (2000) with unpublished data (Sikes) for placement of Diamesus and Oxelytrum. The genus Heterotemna was not sampled.

Introduction

Commonly referred to as the "Large carrion beetles," the subfamily Silphinae has approximately 113 species in 12 extant, validly recognized, genera since the most recent generic changes to the subfamily by Peck (2001).

These beetles are primarily necrophagous, and although they will feed on small carcasses (Bishop, 2001) they usually reproduce only on large carcasses (>300 g). The opposite pattern is seen in the sister subfamily, the Nicrophorinae.

There is a relatively extensive literature on silphid biology, although primarily focused on the more behaviorally complex species of the Nicrophorinae, much of which has been reviewed by Anderson and Peck (1985), Ratcliffe (1996), Eggert and Müller (1997) and Scott (1998). Heymons published a series of classic works describing the biology of various European silphine species (Heymons et al. 1926, 1927, 1928, 1929, 1930a, 1930b; Heymons & Lengerken 1931, 1932a, 1933b, 1934). The life history of Necrodes surniamensis was described by Ratcliffe (1972) but few other silphine species have been studied in detail. See Sikes (in press) for more detailed information on silphid biology, morphology, and phylogeny.

Characteristics

Silphines are dorso-ventrally flattened beetles and along with nicrophorines are among the largest-bodied of the staphylinoids, typically ranging in length from 12-20 mm. Their antennae are eleven segmented, and although the antennae of nicrophorines are eleven segmented also, nicrophorines have a greatly reduced pedicel (antennomere 2) that is fused to the scape (antennomere 1) making them appear to have a 10 segmented antenna. Silphines lack a frontoclypeal (epistomal) suture:

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Head of Oiceoptoma subrufum showing the eleven segmented antennae and the absence of a frontoclypeal suture. Image copyright © 2005 Derek S. Sikes.

The larvae differ between the subfamilies as well with silphine larvae bearing a cluster of 6 stemmata (ocelli) on each side of the head and nicrophorine larvae bearing only a single stemma on each side.

Distribution

The genera, following the most recent classification of the subfamily by Peck (2001) are distributed as follows:

HOLARCTIC:

Aclypea (11 spp)

Necrodes (3 spp.)

Necrophila (18 spp.)

Oiceoptoma (10 spp.)

HOLARCTIC & AFRICA:

Thanatophilus (24 spp.)

EURASIA:

Dendroxena (2 spp.)

EURASIA & AFRICA:

Silpha (26 spp.)

WESTERN NEARCTIC:

Heterosilpha (2 spp.)

SOUTHWESTERN NEARCTIC & NEOTROPICAL:

Oxelytrum (8 spp.)

AUSTRALIA:

Diamesus (2 spp.)

Ptomaphila (3 spp.)

AFRICA - CANARIES:

Heterotemna (3 spp.)

Discussion of Phylogenetic Relationships

Dobler and Müller (2000) inferred the phylogenetic relationships of 9 genera of the Silphinae and 2 of the Nicrophorinae using sequences of the genes COI and COII. Their results were, however, contrary to the conclusions of all prior workers of this family (Hatch, Portevin, Crowson, Hansen, Madge, Newton, et al.) which placed the genera Necrodes and Diamesus basal within the Silphinae (or as a distinct tribe). Dobler and Müller's (2000) study placed Ptomaphila as the basal silphine with Necrodes fully two major branching events from the base of the subfamily. Their placement of Ptomaphila was well supported, and has remained so after the addition of another Ptomaphila species, a species of Oxelytrum (the sister genus of Ptomaphila) and the genus Diamesus, all of which were lacking in their original study (S. Dobler, in litt.; Sikes unpub. data).

If Necrodes + Diamesus are not the most basal Silphinae, and Ptomaphila + Oxelytrum are, then the evolution of various characters will need to be re-evaluated. For example, Necrodes + Diamesus have truncate elytra, and although of quite different forms, this state is shared in general with the Nicrophorinae:

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Truncate elytra in Diamesus (Silphinae) on left and Nicrophorus (Nicrophorinae) on right. Image copyright © 2005 Derek S. Sikes.

Hatch (1927) considered these truncate elytra homologous.

However, given Dobler and Müller's conclusions this character is probably homoplastic: if Ptomaphila and Oxelytrum, which lack truncate elytra, are more closely related to the Nicrophorinae than Necrodes and Diamesus, the truncate elytra of Necrodes + Diamesus are likely to be convergent with the truncate elytra of the Nicrophorinae. For Dobler and Müller's tree to be correct and truncate elytra to be homologous across the basal split of the family would require one extra evolutionary event:

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Alternate character evolution of truncate elytra in the Silphidae assuming the outgroup has truncate elytra. The most parsimonious mapping (A) requires two evolutionary changes: a change from truncate (blue) to nontruncate (yellow) at the base of the Silphinae and a reversal to truncate in the common ancestor of Necrodes + Diamesus. For the truncate elytra to be homologous (B) there would be three parallel evolutionary changes to nontruncate elytra in the Silphinae. Image copyright © 2005 Derek S. Sikes.

Classification

SILPHINAE Latreille, 1807

Silphales Latreille, 1807

Necrodeidae Gistel, 1856

Necrodini Portevin, 1926

The 12 extant genera are as follows, after the most recent classification of the subfamily by Peck (2001), who focused on the Nearctic taxa, with modifications to accomodate Old World and Neotropical taxa based on Madge in litt. Subgenera and junior synonyms are indented below the valid genus name:

Aclypea Reitter, 1884

Blitophaga Reitter, 1884

Dendroxena Motschulsky, 1858

Xylodrepa Thomson, 1859

Diamesus Hope, 1840

Heterosilpha Portevin, 1926

Heterotemna Wollaston, 1864

Necrodes Leach, 1815

Cyclophorus Stephens, 1829

Asbolus Bergroth, 1884

Protonecrodes Portevin, 1922

Necrophila Kirby and Spence, 1828

subgenus Necrophila Kirby & Spence, 1828

Necrobora Hope, 1840

subgenus Eusilpha Semenov-Tian-Shanskij, 1890

subgenus Calosilpha Portevin, 1920

subgenus Deutosilpha Portevin, 1920

subgenus Chrysosilpha Portevin, 1921

Oiceoptoma Leach, 1815

Oeceoptoma Agassiz, 1847

Isosilpha Portevin, 1920

Oxelytrum Gistel, 1848

Hyponecrodes Kraatz, 1876

Katanecrodes Schouteden, 1905

Paranecrodes Portevin, 1921

Ptomaphila Kirby & Spence, 1828

Ptomatophila Agassiz, 1847

Ptomacharis Portevin, 1932

Silpha Linnaeus, 1758

subgenus Silpha Linnaeus, 1758

Parasilpha Reitter, 1884

Carpatosilpha Smetana, 1951

subgenus Phosphuga Leach, 1817

Phosphyga Agassiz, 1847

subgenus Ablattaria Reitter, 1884

Thanatophilus Leach, 1815

Pseudopelta Bergroth, 1884

Philas Portevin, 1903

Silphosoma Portevin, 1903

Chalcosilpha Portevin, 1926

References

Anderson, R. S. & Peck, S. B. 1985. The Carrion Beetles of Canada and Alaska (Coleoptera: Silphidae and Agyrtidae). The Insects and Arachnids of Canada, Part 13. Publication 1778, Research Branch Agriculture Canada, Ottawa. 121 pp

Bishop, A. A. 2001. Niche segregation, carcass preparation, and the effects of land management on the ecology of carrion beetles (Coleoptera: Silphidae) in Kearney County, Nebraska. M.S. Thesis. University of Nebraska at Kearney, 115 pp.

Dobler, S. & Müller, J. K. 2000. Resolving phylogeny at the family level by Mitochondrial Cytochrome Oxidase sequences: Phylogeny of carrion beetles (Coleoptera: Silphidae). Molecular Phylogenetics and Evolution 15(3): 390-402

Eggert, A. -K. & J. K. Müller. 1997. Biparental care and social evolution in burying beetles: Lessons from the larder. pp. 216-236 in Social Behavior in Insects and Arachnids (J. C. Choe, B. J. Crespi, eds.) Cambridge University Press, Cambridge, New York & Oakleigh: v-xiii, 1-541.

Hatch, M. H. 1927. Studies on the Silphinae. Journal of the New York Entomological Society 35: 331-370.

Heymons, R., H. von Lengerken, & M. Bayer. 1926. Studien über die Lebenserscheinungen der Silphini (Coleopt.). I. Silpha obscura L. Zeitschrift für Morphologie und Ökologie der Tiere 6: 287-332.

Heymons, R., H. von Lengerken, & M. Bayer. 1927. Studien über die Lebenserscheinungen der Silphini (Coleopt.). II. Phosphuga atrata L. Zeitschrift für Morphologie und Ökologie der Tiere 9: 271-312.

Heymons, R., H. von Lengerken, & M. Bayer. 1928. Studien über die Lebenserscheinungen der Silphini (Coleopt.). III. Xylodrepa quadripunctata L. Zeitschrift für Morphologie und Ökologie der Tiere 10: 330-352.

Heymons, R., H. von Lengerken, & M. Bayer. 1929. Studien über die Lebenserscheinungen der Silphini (Coleopt). IV. Blitophaga opaca L. (Glattstreifiger Rübenaaskäfer). Zeitschrift für Morphologie und Ökologie der Tiere 14: 234-260.

Heymons, R., H. von Lengerken, & M. Bayer. 1930a. Studien über die Lebenserscheinungen der Silphini (Coleopt.). V. Silpha tyrolensis Laich. Zeitschrift für Morphologie und Ökologie der Tiere 17: 262-274.

Heymons, R., H. von Lengerken, & M. Bayer. 1930b. Studien über die Lebenserscheinungen der Silphini (Coleopt). VI. Blitophaga undata Müll. (Buckelstreifiger Rübenaaskäfer). Zeitschrift für Morphologie und Ökologie der Tiere 18: 170-188.

Heymons, R., & H. von Lengerken. 1931. Studien über die Lebenserscheinungen der Silphini (Coleopt). VII. Oiceoptoma thoracica L. Zeitschrift für Morphologie und Ökologie der Tiere 20: 691-706.

Heymons, R., & H. von Lengerken. 1932a. Studien über die Lebenserscheinungen der Silphini (Coleopt). VIII. Ablattaria laevigata F. Zeitschrift für Morphologie und Ökologie der Tiere 24: 259-287.

Heymons, R., & H. von Lengerken. 1932b. Studien über die Lebenserscheinungen der Silphini (Coleopt). IX. Silpha carinata L. Zeitschrift für Morphologie und Ökologie der Tiere 25: 534-548.

Heymons, R., & H. von Lengerken. 1934. Studien über die Lebenserscheinungen der Silphini (Coleopt). X. Silpha tristis Illig. Zeitschrift für Morphologie und Ökologie der Tiere 28: 469-479.

Ratcliffe, B. C. 1972. The natural history of Necrodes surinamensis (Fabr.) (Coleoptera: Silphidae). Transactions of the American Entomological Society 98: 359-410.

Peck, S. B. 2001. Silphidae. pp. 268-271. in: R. H. Arnett and M. C. Thomas (eds). American Beetles: Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia. Vol.1 Boca Raton: CRC Press. 443 pp.

Scott, M. P. 1998. The ecology and behavior of burying beetles. Annual Review of Entomology 43:595-618.

Sikes, D. S. in press. Silphidae. in: Handbook of Zoology, Hexapoda (Kristensen, N. P. & Beutel, R. G. eds.), Coleoptera I (Beutel, R. G. & Leschen, R. A. B. eds.). De Gruyter, Berlin.