Family Eucnemidae - False Click Beetles
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga (Water, Rove, Scarab, Long-horned, Leaf and Snout Beetles)
No Taxon (Series Elateriformia)
Superfamily Elateroidea (Click, Firefly and Soldier Beetles)
Family Eucnemidae (False Click Beetles)
Other Common Names
Synonyms and other taxonomic changes
(includes Phylloceridae, Perothopidae and Anischiidae)
Explanation of Names
Eucnemidae Eschscholtz 1829
Out of approxomately 1700 species worldwide, only 92 extant spp. have been known to occur in the Nearctic region. There is the potential for many more species extending its range from Mexico into southern California, SE Arizona and southern Texas. Florida may also see many undocumented eucnemid species from the Caribbean, especially with Cuba just 90 miles south of the Florida coastline.
7 out of 9 subfamilies and 15 out of 30 tribes are represented in our area(1)
Family EUCNEMIDAE Eschscholtz, 1829
Subfamily PEROTHOPINAE Lacordaire, 1857
Subfamily PHYLLOCERINAE Reitter, 1905
Tribe Anelastini Reitter, 1921
Kirby, 1818 - Type
Synonymized Type (A. latreillei)
Subfamily PSEUDOMENINAE Muona, 1993
Tribe Schizophilini Muona, 1993
Subfamily PALAEOXENINAE Muona, 1993
Subfamily MELASINAE Fleming, 1821
Tribe Melasini Fleming, 1821
Boisduval & Lacordaire, 1835
Tribe Hylocharini Jacquelin du Val, 1859
Tribe Xylobiini Reitter, 1911
Tribe Epiphanini Muona, 1993
Eschschultz, 1829 - Type
Synonymized Type (E. cristatus)
des Gozis, 1866
Tribe Dirhagini Reitter, 1911
Rhagomicrus thomasi Muona, 2000
Rhagomicrus thoracicus (Horn, 1890)
Golbachia wrighti (Knull, 1946)
LeConte, 1852 - Type
; 2nd Type
Synonymized Type (D. imperfectus)
Microrhagus vulcanicus Wickham - Extinct, Miocene Florissant fossil in Colorado
Fleutiaux, 1935 - two adventive
Otto, Muona & McClarin 2014
Subfamily EUCNEMINAE Eschscholtz, 1829
Tribe Proutianini Muona, 1993
Tribe Dendrocharini Fleutiaux, 1920
Tribe Mesogenini Muona, 1993
Tribe Eucnemini Eschscholtz, 1829
Subfamily MACRAULACINAE Fleutiaux, 1922
Tribe Echthrogasterini Cobos, 1964
Tribe Euryptychini Mamaev, 1976
Tribe Macraulacini Fleutiaux, 1902
Fornax dixiensis Otto, 2017
Fornax knulli Muona, 2000
Fornax relictus Wickham - Extinct, Miocene Florissant fossil in Colorado
(Say, 1836) - Type
Synonymized Type (I. spretus)
Dromaeolus salsus Bonvouloir, 1871
(Horn, 1886) - Type
; 2nd Type
Synonymized Type (N. pavidus)
Asiocnemis boharti Muona, 2000
Muona, 2000 - Type
Replaced name (D. pusillus)
Deltometopus barnowskii Muona, 2000
Deltometopus fossilis Wickham - Extinct, Miocene Florissant fossil in Colorado
Tribe Nematodini Leiler, 1976
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.
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.
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.
|1.||Family-group names in Coleoptera (Insecta)|
Bouchard P. et al. 2011. ZooKeys 88: 1–972.
|3.||A revision of the Nearctic Eucnemidae|
Muona J. 2000. Acta Zoologica Fennica 212: 1-106.