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Family Eucnemidae - False Click Beetles

Deltometopus amoenicornis beetle - Microrhagus triangularis Adelothyreus dejeani Bonvouloir - Adelothyreus dejeani False click beetle ? - Rhagomicrus humeralis Nematodes penetrans Eucnemid - Dromaeolus cylindricollis Beetle - Microrhagus triangularis Beetle - Isorhipis obliqua
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga
No Taxon (Series Elateriformia)
Superfamily Elateroidea
Family Eucnemidae (False Click Beetles)
Other Common Names
Eucnemid Beetles
Synonyms and other taxonomic changes
(includes Phylloceridae, Perothopidae and Anischiidae)
Explanation of Names
Eucnemidae Eschscholtz 1829
>100 spp. in our area, ~2000 total; numerous additions to our fauna may be expected, esp. in FL and along the south border
7 out of 10 subfamilies and 14 out of 29 tribes are represented in our area(1)

Family EUCNEMIDAE Eschscholtz, 1829
Subfamily PEROTHOPINAE Lacordaire, 1857
Genus Perothops Eschscholtz, 1838
Perothops cervinus Germar, 1839
Perothops muscidus (Gyllenhal, 1817)
Perothops witticki LeConte, 1857 - type

Subfamily PHYLLOCERINAE Reitter, 1905
Tribe Anelastini Reitter, 1921
Genus Anelastes Kirby, 1818
Anelastes drurii Kirby, 1818 - Type Synonymized Type (A. latreillei)

Subfamily SCHIZOPHILINAE Muona, 1993
Genus Schizophilus Bonvouloir, 1871
Schizophilus subrufus (Randall, 1838)

Subfamily PALAEOXENINAE Muona, 1993
Genus Palaeoxenus Horn, 1891
Palaeoxenus dohrnii (Horn, 1878) - Type

Subfamily MELASINAE Fleming, 1821
Tribe Melasini Fleming, 1821
Genus Isorhipis Boisduval & Lacordaire, 1835
Isorhipis nubila (Bonvouloir, 1871)
Isorhipis obliqua (Say, 1839)
Genus Melasis Olivier, 1790
Melasis pectinicornis Melsheimer, 1846
Melasis rufipalpis Chevrolat, 1835
Melasis rufipennis Horn, 1886 - Type
Melasis tsugae Hopping, 1926
Tribe Hylocharini Jacquelin du Val, 1859
Genus Hylochares Laporte, 1834
Tribe Xylobiini Reitter, 1911
Genus Xylophilus Mannerheim, 1823
Tribe Epiphanini Muona, 1993
Genus Epiphanis Eschscholtz, 1829
Epiphanis cornutus Eschschultz, 1829 - Type Synonymized Type (E. cristatus)
Genus Hylis des Gozis, 1866
Hylis californicus (Van Dyke, 1932)
Hylis frontosus (Say, 1836)
Hylis irvinei Muona, 2000
Hylis terminalis (LeConte, 1866) - Type
Tribe Dirhagini Reitter, 1911
Genus Protofarsus Muona, 1993
Genus Arrhipis Bonvouloir, 1871
Arrhipis lanieri (Guérin-Méneville, 1843)
Genus Entomophthalmus Bonvouloir, 1871
Entomophthalmus rufiolus (LeConte, 1866) - Type
Genus Rhagomicrus Fleutiaux, 1902
Rhagomicrus thomasi Muona, 2000
Genus Golbachia Cobos, 1955
Golbachia impressicollis (Bonvouloir, 1872)
Golbachia wrighti (Knull, 1946)
Genus Adelothyreus Chevrolat, 1867
Adelothyreus barrae Muona, 2000
Adelothyreus dejeani Bonvouloir, 1872
Genus Microrhagus Dejean, 1833
Microrhagus audax Horn, 1886
Microrhagus opacus Otto, 2015
Microrhagus pectinatus LeConte, 1866 - Type
Microrhagus subsinuatus LeConte, 1852 - Type; 2nd Type Synonymized Type (D. imperfectus)
Microrhagus vulcanicus Wickham - Extinct, Miocene Florissant fossil in Colorado
Genus Dirrhagofarsus Fleutiaux, 1935 - five adventive
Dirrhagofarsus ernae Otto, Muona & McClarin 2014
Dirrhagofarsus lewisi (Fleutiaux, 1900)
Dirrhagofarsus modestus (Fleutiaux, 1923)
Dirrhagofarsus unicolor (Hisamatsu, 1960)
Genus Sarpedon Bonvouloir, 1871
Sarpedon scabrosus Bonvouloir, 1875

Subfamily EUCNEMINAE Eschscholtz, 1829
Tribe Proutianini Muona, 1993
Genus Proutianus Muona, 1993
Proutianus americanus (Horn, 1886) - Type
Tribe Dendrocharini Fleutiaux, 1920
Genus Dendrocharis Guérin-Méneville, 1843
Dendrocharis flavicornis (Guérin-Méneville, 1843)
Tribe Mesogenini Muona, 1993
Genus Vitellius Bonvouloir, 1871
Vitellius texanus Knull, 1957
Genus Stethon LeConte, 1866
Stethon pectorosus LeConte, 1866 - Type
Tribe Eucnemini Eschscholtz, 1829
Genus Eucnemis Ahrens, 1812
Eucnemis americana Horn, 1886 - Type
Genus Idiotarsus Bonvouloir, 1871
Idiotarsus errans (Horn, 1886) - Type

Subfamily MACRAULACINAE Fleutiaux, 1922
Tribe Echthrogasterini Cobos, 1964
Genus Hemiopsida MacLeay, 1872
Hemiopsida robusta (Van Dyke, 1943)
Tribe Euryptychini Mamaev, 1976
Genus Euryptychus LeConte, 1852
Euryptychus arizonicus (Van Dyke, 1945)
Euryptychus ulkei (Horn, 1886) - Type
Tribe Macraulacini Fleutiaux, 1902
Genus Diphytaxis Horn, 1890
Genus Onichodon Newman, 1838
Onichodon canadensis (Brown, 1940)
Onichodon downiei Muona, 2000
Onichodon orchesides Newman, 1838
Onichodon rugicollis (Fall, 1925) - Type
Onichodon wappesi Muona, 2000
Genus Serrifornax Fleutiaux, 1926
Serrifornax infelix (Horn, 1886) - Type
Genus Fornax Laporte, 1835
Fornax bicolor (Melsheimer, 1844)
Fornax dixiensis Otto, 2017
Fornax floridana Otto, 2020
Fornax knulli Muona, 2000
Fornax melsheimeri Otto, 2020
Fornax relictus Wickham - Extinct, Miocene Florissant fossil in Colorado
Genus Isarthrus LeConte, 1852
Isarthrus calceatus (Say, 1836) - Type Synonymized Type (I. spretus)
Isarthrus rufipes (Melsheimer, 1844)
Genus Absensiugum Otto, Muona & Cordoba-Alfaro, 2023
Absensiugum teres (Horn, 1886) - Type; 2nd Type Synonymized Type (N. pavidus)
Genus Dromaeolus Kiesenwetter, 1858
Dromaeolus badius (Melsheimer, 1844)
Dromaeolus californicus Bonvouloir, 1875 - Type
Dromaeolus punctatus (LeConte, 1878) - Type
Dromaeolus salsus Bonvouloir, 1871
Dromaeolus striatus (LeConte, 1852) - Type
Dromaeolus turnbowi Muona, 2000
Genus Asiocnemis Mamaev, 1976
Asiocnemis basalis (LeConte, 1866) - Type
Asiocnemis boharti Muona, 2000
Asiocnemis hospitalis (Blanchard, 1904) - Type
Asiocnemis mcclayi Muona, 2000
Asiocnemis nitens (Horn, 1886) - Type
Genus Thambus Bonvouloir, 1871
Thambus horni Muona, 2000 - Type Replaced name (D. pusillus)
Genus Deltometopus Bonvouloir, 1871
Deltometopus fossilis Wickham - Extinct, Miocene Florissant fossil in Colorado
Tribe Nematodini Leiler, 1976
Genus Nematodes Berthold, 1827
Nematodes atropos (Say, 1836)
Nematodes collaris Bonvouloir, 1872
Nematodes humpreyi Muona, 2000
Nematodes penetrans (LeConte, 1852) - Type
2.9-25.0 mm
The most compelling trait used to differentiate adult members of the family from its close relatives, the elaterids is how the second antennomere is placed on the basal segment.
Eucnemid beetles will have the second antennomere placed subterminally (off set to the side) from the first one.
Elaterid beetles will have their second antennomere placed at the terminal end of the first segment.
Other traits used for identifying eucnemids from elaterids include the lack of a free labrum and the anterior margin of the prosternum being straight rather than lobed. The anterior margin of the prosternum should not be used as definitive means to separate the two families, since primitive members of Eucnemidae will have that lobed anterior margin of the prosternum much like Elateridae.

Often referred to as wireworms and cross-grain borers. Four larval forms exist:
Buprestiform -- Larvae are not heavily armored. They are less sclerotized. They are often whitish in color with a well expanded prothoracic segment, much like the larvae of Buprestidae. These larvae will also have extremely small mandibles with outwardly projecting teeth. Some larvae will have some velvety patches on the surface of the segments and also will have elaborately shaped scleromes on the prothorax in the shape of a "T" or an inverted "L".
Elateriform -- Larvae are heavily armored or sclerotized. They are usually yellow-brown in color, wire-like in form and similar to larvae of Elateridae. The best way to identify these larvae from other families is to look at the highly modified head under magification. These larvae will have lateral teeth on the outside edge of the head capsule. Their mandibles are extremely small with outwardly projecting teeth. The surface of each segment will be covered with velvety patches called microtricial patches.
Fusiform -- Larvae are usually not heavily armored. They are often whitish in color with well expanded segments, similar to a hymenopteran or dipteran larval types. Head capsules are either simplified and fleshy or armed with four to six anteriorally projecting teeth. Mandibles are not present, but possess a buccal region with labial and maxillary palpi. Larval types are primarily found in the tropics, but in case of the Nearctic region, may be present in two possibly three pantropical genera.
Onisciform -- Larvae are heavily armored or sclerotized as in the Elateriform larvae. Colorations are similar as well. The larval form is generally flatter, with wider than long thoracic and abdominal segments. The best example of this form is the Dohrn's Elegant Eucnemid Beetle in Southern California.
All continents except for Antarctica; most diverse in the tropical and subtropical regions
Found largely in woodlands and forests, especially with a diverse forest structure and plenty of dead wood for breeding. Adults are found in the tree canopies and on/under tree bark. Larvae are either in moist dead wood, hard seasoned wood or thrive in the soil near the roots of dead/dying trees. Fungi are usually present in those situations where larvae have been found.
see also(2)
The season will vary depending on region. The southern US will see adults as early as March and April. The Pacific Northwest will also see adult beetles pretty early in the season, as early as April. Upper Midwest, NE and lower sections of western NA will be later (mid May/early June). In general, season will run from late March through about the middle of September.
Unknown if adults have any food preferences. Larvae may be feeding on fungal mycelia found in moist or hard wood. Some believe they may have a liquid diet.
Life Cycle
Some species undergo a hypermetamorphic lifecycle, with a first instar being a free-living non-parasitic triungulin. It will molt into a completely different larval form later on. Some fifth instar larvae will transition into a prepupal stage, before entering the pupal stage.
Some eucnemid larvae, espcially those similar to elaterid larvae have been observed to bore along the grain of the wood. Other larvae (buprestiform), on the other hand have been known to cut across the grain of the wood, hence the name cross-grain borers. In all observations, these immature beetles are usually found within two to three inches from the surface in the sapwood.
Most Nearctic eucnemid species overwinter as larvae and continue development in the following spring. Many species complete development in one to two years. Some will complete it in three years. Pupal cells are constructed near the surface and larvae have been seen doubled-up in a u-shaped position. Timing in their development hinges on the availability of food sources, moisture and temperature and may arrest its development until suitable conditions are met.
"The term false click beetle was a misnomer, believing these beetles are incapable of snapping into the air. In fact, many species of false click beetles can actually click. The common name is just a means to distinguish eucnemids from the true click beetles for different reasons, largely by the lack of a free labrum and straight anterior margin of the prosternum, just below the head." --Robert Otto, 3.v.2008
Eucnemidae may play an important role in the interactions between trees, fungi and forest regeneration, and be good indicators of the diverse forest structure.... The presence and numbers of these beetles can and should be used when planning conservation measures and sustainable forestry."(3)
Factors that may limit the numbers of Eucnemidae in a forest system are poor forestry practices, arboreal diseases, introductions of exotic biota and over harvesting of dead wood for fire wood.
False click beetles are the exclusive hosts of an entire family of parasitic wasps, Vanhorniidae.(4)
Larvae of Eucnemidae bore across the grain.(5)
See Also
Cerophytidae · Throscidae · Elateridae · Melandryidae (esp. Enchodes, Orchesia and Rushia)
Works Cited
1.Family-group names in Coleoptera (Insecta)
Bouchard P. et al. 2011. ZooKeys 88: 1–972.
2.Review of the phylogeny, classification and biology of the family Eucnemidae (Coleoptera)
Muona J. 1993. Entomologica Scandinavica Suppl. 44: 1-133.
3.A revision of the Nearctic Eucnemidae
Muona J. 2000. Acta Zoologica Fennica 212: 1-106.
4.Hidden Company that Trees Keep: Life from Treetops to Root Tips
James B. Nardi. 2023. Princeton University Press.
5.The World Beneath our Feet: A Guide to Life in the Soil
James B. Nardi. 2003. Oxford University Press.