Rain beetle

The rain beetles are a group of beetles found in the far west of North America. They spend most of their lives underground, emerging in response to rain or snow, thus the common name. Formerly classified in 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,[1] and Proteroscarabeus of Late Cretaceous China.[2]

Possessing a robust oval body form similar to other scarabaeiforms, their ventral side is densely covered with fine, long hairs (genus name derives from Greek πλείων (ple-, abundant) and κόμη (kome, hair), extending to the legs and to the margins of thorax and elytra. The back is hairless and glossy. Overall colors range from black to a reddish-brown, while the hairs may range from yellow to red to black. The antennae are 11-segmented, with a club of four to eight lamellae, more than in any other group of the Scarabaeoidea. The mandibles are not functional, and the opening into the esophagus is closed off; adults do not eat.

Larvae have the typical scarabaeiform characteristics, C-shaped bodies generally a creamy white. They feed on roots in the soil, often deep beneath the host plant. Details of the larval stage are only known for some species; they have nine or more instars, and may take up to 13 years to mature. After a late summer pupation, adults of both sexes dig their way to the surface, emerging around the onset of the fall/winter rainy season typical of, for instance, California's climate; some species are active as late as early spring. Females have only vestigial wings, so the males fly around (often while it is raining), homing in on pheromones released by the females. They mate on the surface or in a burrow dug out by the female, then the female lays eggs in the bottom of the burrow. The "triggering" conditions required for some species to fly are so stringent that a given population may only be active for a single day in a given year. Males are commonly attracted to bright lights.

Members of Pleocoma are known from extreme southern Washington, throughout the mountains of Oregon and California, and into the extreme north of Baja California.

Rain beetles
Temporal range: Late Cretaceous–recent
Pleocoma
Pleocoma
Scientific classification
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Pleocomidae

LeConte, 1861
Genera
  • Pleocoma LeConte, 1856
  • Cretocoma Nikolaev, 2002
  • Proteroscarabeus Grabau 1923

References

  1. ^ Frank-Thorsten Krell. "Catalogue of fossil Scarabaeoidea (Coleoptera: Polyphaga) of the Mesozoic and Tertiary" (PDF). Natural History Museum. Archived from the original (PDF) on July 20, 2011. Retrieved March 7, 2011.
  2. ^ Krell, Frank-Thorsten. "The fossil record of Mesozoic and Tertiary Scarabaeoidea (Coleoptera: Polyphaga)." Invertebrate Systematics 14.6 (2000): 871-905.

External links

Carabus violaceus

Carabus violaceus, sometimes called the violet ground beetle, or the rain beetle is a nocturnal species of a beetle, from a family Carabidae.

Pleocoma

Pleocoma is a genus of rain beetles in the family Pleocomidae. There are 27 described species in Pleocoma.

Pleocoma australis

Pleocoma australis, the southern rain beetle, is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma blaisdelli

Pleocoma blaisdelli is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma carinata

Pleocoma carinata is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma conjungens

Pleocoma conjungens, the Santa Cruz rain beetle, is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma crinita

Pleocoma crinita is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma dubitabilis

Pleocoma dubitabilis is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma fimbriata

Pleocoma fimbriata is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma hirticollis

Pleocoma hirticollis is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma linsleyi

Pleocoma linsleyi is a beetle of the Rain beetle family. It was named in honor of American entomologist Earle Gorton Linsley

Pleocoma minor

Pleocoma minor is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma puncticollis

Pleocoma puncticollis, the black rain beetle, is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma rickseckeri

Pleocoma rickseckeri is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma shastensis

Pleocoma shastensis is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma simi

Pleocoma simi is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma sonomae

Pleocoma sonomae is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma staff

Pleocoma staff is a species of rain beetle in the family Pleocomidae. It is found in North America.

Pleocoma tularensis

Pleocoma tularensis is a species of rain beetle in the family Pleocomidae. It is found in North America.

Extant Coleoptera families

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