Eleodes (commonly known as pinacate beetles or desert stink beetles) is a genus of darkling beetles in the family Tenebrionidae. They are endemic to western North America, ranging from southern Canada to central Mexico, with many species found along the Mexico-United States border. Some species have been introduced to Colombia. The name pinacate is Mexican Spanish, derived from the Nahuatl (Aztec) name for the insect, pinacatl, which translates as "black beetle".

Eleodes species range from about 10 to 50 millimetres (0.39 to 1.97 in) in length and are black, with some having a reddish tint on their abdomen. The setae of some species such as Eleodes osculans collect debris and give the insect a brown color, a similar effect occurs in the species Eleodes mirabilis giving it the appearance of having whitish stripes on its abdomen. Due to the number of species and their large range these beetles have a fairly varied appearance throughout the many species. All produce quinone or similar substances as a deterrent to predators, and many will stand on their heads to spray it. They are typically found in the arid desert regions of their range, but can also be found in forests and grasslands. All Eleodes species are flightless as their elytra are fused together and their second pair of wings is very reduced and vestigial.

Ecology

Most members of the genus Eleodes are primarily detrivores feeding on plant and animal debris. Some species are more inclined to consume living plants, which is especially true for species native to the plains of North America, such as Eleodes hispilabris and Eleodes opaca. The larvae of those species and others are considered pests as they feed on the roots of crops.

Species found in dry regions, such as members of the subgenus Eleodes, are usually much larger than what is expected for most insects, this is due the lack of water in the area leading to these beetles evolving larger bodies in order to hold more of it. Water loss is also the reason that the elytra are fused in Eleodes. As expected, species found in forests, such as members of the subgenus Blapylis, are smaller, closer to the size of most other insects.

Eleodes are generally more active at night; some species are strictly nocturnal while others can and will be active during the day. As these beetles are fairly long-lived for insects, they must adapt to the different seasons. During the fall, they are diurnal as it is warmest during the day. When winter comes, they take shelter and become inactive so as not to freeze in the cold. When spring arrives, they go back to being active during the day until the summer when they switch to being active at night to survive the deadly high temperatures of the desert. Eleodes take shelter almost anywhere that can protect them from the hot and cold. This can be wood or rocks, but is often rodent burrows. Every night when these beetles scavenge for food, they pick a new shelter for the day, which, if not suitable for protection against the elements, will be abandoned in search of a new one. One subgenus, Caverneleodes, lives only in caves, cave-like environments, or rock crevices. These beetles have reduced eyes and only leave their hideouts to scavenge for food.

Chemical defense

Beetles within Eleodes and other genera within Tenebrionidae exude a foul-smelling odor and a very distasteful liquid from glands to ward off predators. This liquid is most commonly a quinone. While not being poisonous the liquid does usually deter predators, the success of this defense mechanism has led to the evolution of a Müllerian mimicry complex among Eleodes acuticauda, Eleodes dentipes, and Coelocnemis magna, the latter of which while not being within Eleodes is a still distasteful prey item. All three previously mentioned species look strikingly similar, leading to a strengthened defense against potential predators. Another Müllerian mimicry complex exists between Eleodes scabrosa and Eleodes tuberculata. The "head-standing" behavior exhibited by these beetles is aposematic. By leaving their presence and identity unambiguous to potential predators, it means that more individuals can survive as predators will avoid beetles with the "head-standing" behavior.

While this defense is generally effective in deterring predators, they are still preyed upon by many species, such as owls, foxes, coyotes, skunks, bats, turtles, etc.

Fossil record and evolution

Fossils of Eleodes acuticauda, Eleodes osculans, Eleodes carbonaria, Eleodes granulata, Eleodes gracilis, and others have been found in the La Brea Tar Pits, Carpinteria Tar Pits, and the Snowmastodon Site which are all dated to the Pleistocene epoch. Eleodes split off from the rest of Amphidorini at least 8 to 15 million years ago in the Miocene, although this estimate is likely on the lower side due to low taxon sampling.

Taxonomy

Eleodes is the largest New World genus of darkling beetles comprising around 200 species divided up into the following 17 subgenera.

Subgenera:

  • Subgenus Amphidora Eschscholtz, 1829 Eleodes littoralis Eschscholtz, 1829 Eleodes nigropilosa LeConte, 1851 Eleodes subdeplanta Blaisdell, 1943
  • Subgenus Ardeleodes Eleodes tibialis Blaisdell, 1909
  • Subgenus Blapylis Horn, 1870 Eleodes alticola Blaisdell, 1925 Eleodes aristata Somerby, 1977 Eleodes bishopensis Somerby and Doyen, 1976 Eleodes blanchardii Blaisdell, 1909 Eleodes brunnipes Casey, 1890 Eleodes caseyi Blaisdell, 1909 Eleodes clavicornis Eschscholtz, 1829 Eleodes consobrina LeConte, 1851 Eleodes constricta LeConte, 1858 Eleodes cooperi Somerby and Doyen, 1976 Eleodes cordata Eschscholtz, 1829 Eleodes fuchsii Blaisdell, 1909 Eleodes hoppingii Blaisdell, 1909 Eleodes hornii Blaisdell, 1909 Eleodes hybrida Blaisdell, 1917 Eleodes inculta LeConte, 1861 Eleodes kaweana Blaisdell, 1933 Eleodes lariversi Somerby and Doyen, 1976 Eleodes lecontei Horn, 1870 Eleodes manni Blaisdell, 1917 Eleodes nana Blaisdell, 1909 Eleodes neotomae Blaisdell, 1909 Eleodes novoverrucula Boddy, 1957 Eleodes nunenmacheri Blaisdell, 1918 Eleodes oregona Blaisdell, 1941 Eleodes orophila Somerby, 1977 Eleodes panamintensis Somerby, 1977 Eleodes parvicollis Eschscholtz, 1829 Eleodes patulicollis Blaisdell, 1932 Eleodes pimelioides Mannerheim, 1843 Eleodes planata Eschscholtz, 1829 Eleodes producta Mannerheim, 1843 Eleodes propinqua Blaisdell, 1918 Eleodes robinetti Boddy, 1957 Eleodes rotundipennis LeConte, 1857 Eleodes scabripennis LeConte, 1859 Eleodes scabriventris Blaisdell, 1932 Eleodes scabrosa Eschscholtz, 1829 Eleodes schlingeri Somerby and Doyen, 1976 Eleodes schwarzii Blaisdell, 1909 Eleodes snowii Blaisdell, 1909 Eleodes spilmani Somerby and Doyen, 1976 Eleodes strumosa Blaisdell, 1932 Eleodes subvestita (Blaisdell, 1939) Eleodes tenebrosa Horn, 1870 Eleodes triplehorni Somerby and Doyen, 1976 Eleodes trita Blaisdell, 1917 Eleodes tuberculata Eschscholtz, 1829 Eleodes versatilis Blaisdell, 1921 Eleodes volcanensis Somerby, 1977 Eleodes wakelandi Somerby, 1977
  • Subgenus Caverneleodes Triplehorn, 1975 Eleodes easterlai Triplehorn, 1975 Eleodes gruta Aalbu, Smith & Triplehorn, 2012 Eleodes guadalpensis Aalbu, Smith & Triplehorn, 2012 Eleodes labialis Triplehorn, 1975 Eleodes leptoscelis Triplehorn, 1975 Eleodes microps Aalbu, Smith & Triplehorn, 2012 Eleodes reddelli Triplehorn, 2007 Eleodes rugosifrons Triplehorn & Reddell, 1991 Eleodes sprousei Triplehorn & Reddell, 1991 Eleodes thomasi Aalbu, Smith & Triplehorn, 2012 Eleodes wheeleri Aalbu, Smith & Triplehorn, 2012 Eleodes wynnei Aalbu, Smith & Triplehorn, 2012
  • Subgenus Chaseleodes Thomas, 2015 Eleodes connata Solier, 1848 Eleodes curta Champion, 1884
  • Subgenus Cratidus LeConte, 1862 Eleodes osculans LeConte, 1851 Eleodes ursus Triplehorn, 1996
  • Subgenus Discogenia LeConte, 1866 Eleodes acutangula Blaisdell, 1921 Eleodes marginata Eschscholtz, 1829 Eleodes scabricula LeConte, 1858
  • Subgenus Eleodes Eschscholtz, 1829 Eleodes acuta (Say, 1824) Eleodes acuticauda LeConte, 1851 Eleodes adumbrata Blaisdell, 1925 Eleodes armata LeConte, 1851 Eleodes curvidens Triplehorn & Cifuentes-Ruiz, 2011 Eleodes dentipes Eschscholtz, 1829 Eleodes discincta Blaisdell, 1925 Eleodes eschscholtzii Solier, 1848 Eleodes femorata LeConte, 1851 Eleodes fiski Triplehorn, 2015 Eleodes gracilis LeConte, 1858 Eleodes grandicollis Mannerheim, 1843 Eleodes hispilabris (Say, 1824) Eleodes loretensis Blaisdell, 1923 Eleodes mexicana Blaisdell, 1943 Eleodes mirabilis Triplehorn, 2007 Eleodes moesta Blaisdell, 1921 Eleodes muricatula Triplehorn, 2007 Eleodes obscura (Say, 1824) Eleodes rossi Blaisdell, 1943 Eleodes rugosa Perbosc, 1839 Eleodes samalayucae Triplehorn, 2007 Eleodes sanmartinensis Blaisdell, 1921 Eleodes scyroptera Triplehorn, 2007 Eleodes spinipes Solier, 1848 Eleodes sponsa LeConte, 1858 Eleodes subcylindrica Casey, 1890 Eleodes suturalis (Say, 1824) Eleodes tenuipes Casey, 1890 Eleodes vanduzeei Blaisdell, 1923
  • Subgenus Heteropromus Blaisdell, 1909 Eleodes veterator Horn, 1874
  • Subgenus Litheleodes Blaisdell, 1909 Eleodes arcuata Casey, 1884 Eleodes aspera LeConte, 1866 Eleodes corvina Blaisdell, 1921 Eleodes extricata (Say, 1824) Eleodes granulata LeConte, 1857 Eleodes hirtipennis Triplehorn, 1964 Eleodes letcheri Blaisdell, 1909 Eleodes papillosa Blaisdell, 1917 Eleodes subtuberculata Walker, 1866
  • Subgenus Melaneleodes Blaisdell, 1909 Eleodes tricostata (Say, 1824) Eleodes neomexicana Blaisdell, 1909 Eleodes pedinoides LeConte, 1858 Eleodes wenzeli Blaisdell, 1925 Eleodes parowana Blaisdell, 1925 Eleodes halli Blaisdell, 1941 Eleodes carbonaria (Say, 1824) Eleodes quadricollis Eschscholtz, 1829 Eleodes anthracina Blaisdell, 1909 Eleodes humeralis LeConte, 1857 Eleodes rileyi Casey, 1891 Eleodes rufipes Pierre, 1976
  • Subgenus Metablapylis Blaisdell, 1909 Eleodes aalbui Triplehorn, 2007 Eleodes californica Blaisdell, 1929 Eleodes delicata Blaisdell, 1929 Eleodes dissimilis Blaisdell, 1909 Eleodes nevadensis Blaisdell, 1909 Eleodes nigrina LeConte, 1858
  • Subgenus Omegeleodes Triplehorn & Thomas, 2011 Eleodes debilis LeConte, 1858
  • Subgenus Promus LeConte, 1862 Eleodes anachronus Triplehorn, 2010 Eleodes bidens Triplehorn, 2007 Eleodes brucei Triplehorn, 2007 Eleodes calcarata Champion, 1884 Eleodes composita Casey, 1891 Eleodes erratica Champion, 1884 Eleodes exarata Champion, 1884 Eleodes fusiformis LeConte, 1858 Eleodes goryi Solier, 1848 Eleodes hoegei Champion, 1884 Eleodes insularis Linell, 1899 Eleodes knullorum Triplehorn, 1971 Eleodes longicornis Champion, 1884 Eleodes madrensis Johnston, 2015 Eleodes montana Champion, 1884 Eleodes opaca (Say, 1824) Eleodes spiculifera Triplehorn, 2007 Eleodes spinolae Solier, 1848 Eleodes striolata LeConte, 1858 Eleodes subnitens LeConte, 1851 Eleodes watrousi Triplehorn, 2007
  • Subgenus Pseudeleodes Blaisdell, 1909 Eleodes caudifera LeConte, 1858 Eleodes granosa LeConte, 1866 Eleodes inornata Johnston, 2016 Eleodes leechi Tanner, 1961 Eleodes longipilosa Horn, 1891 Eleodes pilosa Horn, 1870 Eleodes spoliata Blaisdell, 1933 Eleodes tribulus Thomas, 2005
  • Subgenus Steneleodes Blaisdell, 1909 Eleodes angulata (Eschscholtz, 1829) Eleodes angusta Eschscholtz, 1829 Eleodes blapoides Eschscholtz, 1829 Eleodes coarctata Champion, 1885 Eleodes corrugans Triplehorn, 2007 Eleodes distincta Solier, 1848 Eleodes forreri Champion, 1884 Eleodes gigantea Mannerheim, 1843 Eleodes glabricollis Champion, 1884 Eleodes gravida (Eschscholtz, 1829) Eleodes hepburni Champion, 1884 Eleodes innocens LeConte, 1866 Eleodes laevigata Solier, 1848 Eleodes longicollis LeConte, 1851 Eleodes mutilata Blaisdell, 1921 Eleodes olida Champion, 1892 Eleodes ornatipennis Blaisdell, 1937 Eleodes peropaca Champion, 1892 Eleodes platypennis Triplehorn, 2007 Eleodes ponderosa Champion, 1884 Eleodes punctigera Blaisdell, 1935 Eleodes ruida (Say, 1835) Eleodes sallaei Champion, 1885 Eleodes solieri Champion, 1885 Eleodes stolida Champion, 1885 Eleodes sulcatula Champion, 1884 Eleodes tenebricosa Gemminger, 1870 Eleodes tessellata Champion, 1892
  • Subgenus Tricheleodes Blaisdell, 1909 Eleodes hirsuta LeConte, 1861

Incertae sedis:

  • Eleodes aequalis (Say, 1835) Eleodes amaura Champion, 1892 Eleodes barbata Wickham, 1918 Eleodes brevicollis Gemminger, 1870 Eleodes cylindrica (Herbst, 1799) Eleodes dilaticollis Champion, 1884 Eleodes ebenina (Solier, 1848) Eleodes elongatula Eschscholtz, 1829 Eleodes impolita (Say, 1835) Eleodes maura (Say, 1835) Eleodes melanaria Eschscholtz, 1829 Eleodes obliterata (Say, 1835) Eleodes polita Champion, 1892 Eleodes rotundicollis (Eschscholtz, 1829) Eleodes scapularis Champion, 1884 Eleodes segregata Champion, 1892 Eleodes striata (Guérin-Méneville, 1834) Eleodes sulcata (Eschscholtz, 1829)

Notes

See also

External links