Rain beetle
{{Short description|Family of beetles}}
{{Automatic taxobox
| name = Rain beetles
| fossil_range = {{fossil_range|Late Cretaceous|recent}}
| image = Pleocoma.jpg
| image_caption = Pleocoma
| display_parents = 3
| taxon = Pleocomidae
| authority = LeConte, 1861
| subdivision_ranks = Genera
| subdivision =
- Pleocoma LeConte, 1856
- †Cretocoma Nikolaev, 2002
- †Proteroscarabeus Grabau 1923
}}
The rain beetles are a group of beetles whose extant species are found only in the far west of North America.{{cite web |last1=Hovore |first1=Frank T. |title=Generic Guide to New World Scarab Beetles |url=http://unsm-ento.unl.edu/Guide/Scarabaeoidea/Pleocomidae/Pleocomidae-Overview/PleocomidaeO.html |website=unsm-ento.unl.edu |publisher=University of Nebraska State Museum - Division of Entomology |access-date=14 December 2020}} They spend most of their lives underground, emerging in response to rain or snow, thus the common name. Formerly classified in the Scarabaeidae (and later the Geotrupidae), they are currently assigned to their own family Pleocomidae, considered the sister group to all the remaining families of Scarabaeoidea. The family contains a single extant genus, Pleocoma, and two extinct genera, Cretocoma, described in 2002 from Late Cretaceous deposits in Mongolia,{{Cite web |url=http://www.unl.edu/museum/research/entomology/fossilrecord-web.pdf |format=PDF |title=Catalogue of fossil Scarabaeoidea (Coleoptera: Polyphaga) of the Mesozoic and Tertiary |author=Frank-Thorsten Krell |publisher=Natural History Museum |access-date=March 7, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110720095415/http://www.unl.edu/museum/research/entomology/fossilrecord-web.pdf |archive-date=July 20, 2011 }} and Proteroscarabeus of Late Cretaceous China.Krell, Frank-Thorsten. "The fossil record of Mesozoic and Tertiary Scarabaeoidea (Coleoptera: Polyphaga)." Invertebrate Systematics 14.6 (2000): 871-905.
Biology
Adult rain beetles lack functioning mouthparts and are unable to feed. Instead, they rely on fat storage from when they were larvae. Larvae feed on the roots of shrubs and trees, as well as fungi and other organic matter. {{Cite web |title=Rain Beetles Are Curious Critters |url=https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19974 |access-date=2024-10-31 |website=ANR Blogs |language=en-us}} Larvae feeding on orchard trees can result in patches or winding bands on tree roots, and ultimately causes reduced foliage and fruit yield for trees.{{Cite web |title=Rain Beetles {{!}} WSU Tree Fruit {{!}} Washington State University |url=https://treefruit.wsu.edu/crop-protection/opm/rain-beetles/ |access-date=2024-03-16 |language=en-US}}
Rain beetles spend most of their lives as larvae underground, burrowing up to twelve feet below the surface. Larvae can live between 7 and 14 years before they pupate into adulthood. They need at least seven instars, or developmental stages between molts, before they can pupate, but some may take more.{{Cite web |last=Parent |first=Emily |title=Hike with a scientist: Seeking the secrets of Oregon’s mysterious rain beetles in Corvallis |url=https://www.statesmanjournal.com/story/travel/outdoors/hikes/2022/11/18/corvallis-oregon-state-university-entomologist-rain-beetles-west-coast-hiking/69617221007/ |access-date=2024-10-31 |website=Statesman Journal |language=en-US}}
Male rain beetles exhibit most mating behavior during winter nights. As the females are flightless, the males spend a large portion of time walking on snow in search of them. This also limits the known modern distribution of the beetles.{{Cite book |url=https://www.degruyter.com/document/doi/10.1525/9780520937567/html |title=Introduction to California Beetles |date=2005-12-31 |publisher=University of California Press |isbn=978-0-520-93756-7 |editor-last=Evans |editor-first=Arthur V. |doi=10.1525/9780520937567 |editor-last2=Hogue |editor-first2=James N.}} The male's ability to maintain a high internal temperature, up to 95 degrees, is critical to their mating and survival prospects, as their thoracic pile is ineffective insulation.{{Cite journal |last=Morgan |first=Kenneth R. |date=1987-03-01 |title=Temperature Regulation, Energy Metabolism and Mate-Searching in Rain Beetles (Pleocoma Spp.), Winter-Active, Endothermic Scarabs (Coleoptera) |url=http://dx.doi.org/10.1242/jeb.128.1.107 |journal=Journal of Experimental Biology |volume=128 |issue=1 |pages=107–122 |doi=10.1242/jeb.128.1.107 |issn=0022-0949|url-access=subscription }}
The lifespan of adult rain beetles is also dependent on their sex. The males live only a few days, expending most of their energy in search of mates, while the females can survive a few months in their burrow.
Distribution
Most rain beetle populations are in mountainous California. They have not been found in the desert but also live in parts of the Sacramento Valley and coastal plain of the San Diego Valley. Extant members of Pleocoma are known from extreme southern Washington, throughout the mountains of Oregon and California, and into the extreme north of Baja California.
References
{{Reflist}}
- {{cite book |author=Frank T. Hovore |chapter=Pleocomidae |editor=Ross H. Arnett, Jr. |editor-link=Ross H. Arnett, Jr. |editor2=Michael C. Thomas |editor2-link=Michael C. Thomas |editor3=Paul E. Skelley |editor4=J. Howard Frank |series=American Beetles |publisher=CRC Press |year=2002 |title=Volume 2: Polyphaga: Scarabaeoidea through Curculionoidea |isbn=0-8493-0954-9 |pages=20–22}}
External links
{{Portal|Insects}}
- {{Wikispecies-inline|Pleocomidae}}
{{Coleoptera|4}}
{{Taxonbar|from=Q311154}}