| Rain beetles | |
|---|---|
 | |
| Pleocoma | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Suborder: | Polyphaga |
| Infraorder: | Scarabaeiformia |
| Superfamily: | Scarabaeoidea |
| Family: | Pleocomidae LeConte, 1861 |
| Genera | |
| |
Therain beetles are a group ofbeetles whose extant species are found only in the far west ofNorth America.[1] They spend most of their lives underground, emerging in response to rain or snow, thus the common name. Formerly classified in theScarabaeidae (and later theGeotrupidae), they are currently assigned to their own familyPleocomidae, considered thesister group to all the remaining families ofScarabaeoidea. The family contains a singleextant genus,Pleocoma, and twoextinct genera,Cretocoma, described in 2002 fromLate Cretaceous deposits inMongolia,[2] andProteroscarabeus of Late CretaceousChina.[3]
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.[4] 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.[5]
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.[6]
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.[7] The male's ability to maintain a high internal temperature, up to 95 degrees, is critical to their mating and survival prospects, as theirthoracic pile is ineffective insulation.[8]
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.[7]
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 ofPleocoma are known from extreme southernWashington, throughout the mountains ofOregon andCalifornia, and into the extreme north ofBaja California.[1]
Data related toPleocomidae at Wikispecies