Epomis

Epomis
Epomis dejeani eating a fire salamander, Salamandra salamandra
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Carabidae
Subfamily: Licininae
Tribe: Chlaeniini
Genus: Epomis
Bonelli, 1810
Epomis circumscriptus preying upon a tree frog, Hyla savignyi

Epomis is a genus of ground beetles (Carabidae). The larvae of this genus are notable for being obligate role reversal predators.[1] Amphibians such as frogs are normally predators of beetles, however Epomis larvae feed exclusively on amphibians.

Description

Epomis beetles are often metallic blue or green colored, with a striking yellow-orange rim on the elytra and mostly yellow-colored legs and antennae.[2] They are 15-26 millimeters in length.[3] They can be distinguished from the closely related genus Chlaenius by the short (less than three times as long as wide) and triangular labial palps.[2]

The larvae reach a body length of up to 20 millimeters, they are white or yellow colored, with black and orange markings. Like many ground beetle larvae they are elongated with two extensions (Urogomphi) at the rear end. They have characteristic double-hooked mandibles. Larvae of the two European species can be distinguished by their color pattern.[4]

Feeding behavior

Epomis larvae hunt in a rare reversal of the usual predator-prey relationship between amphibians and insects. They lure their amphibian predators by making prey-like movements, then evade the predator's attack and disable the predator, often with a bite to the throat or underside.[1] After the attack, the larva stays attached to the amphibian while feeding on it, similarly to external parasites.[1][5][6] Adult Epomis beetles are generalist predators but can also feed on amphibians.[7][8] They sneak up behind their victims, and hold on firmly using their legs. To paralyze the victim, the beetle makes an incision in the pelvic region with its mandibles. There is speculation that the incision cuts leg muscles.[9] The amphibian loses its ability to move and is eaten by the beetle. Scientists speculate that Epomis evolved this behavior as an aggressive evasion tactic in response to predation by amphibians and the success of this tactic led to Epomis becoming an obligate predator itself.[1]

Epomis circumscriptus larva displaying luring movements of antennae and mouthparts


A juvenile toad is attracted and lured to an ambushing Epomis dejeani larva

Taxonomic status

The genus Epomis belongs to tribe Chlaeniini in the subfamily Licininae, which consists of species associated with swamps, temporary ponds and similar types of wetland habitats.[7] It contains about 30 species distributed in the old world only, with the majority of species occurring in the Afrotropical region.[3][10] Many taxonomists consider Epomis as a subgenus of Chlaenius, however differences in larval and adult morphology, as well as the unique life history of Epomis beetles, support their separate standing as a genus.[11]

List of species

References

  1. 1 2 3 4 Gil Wizen & Avital Gasith (2011). "An unprecedented role reversal: ground beetle larvae (Coleoptera: Carabidae) lure amphibians and prey upon them". PLoS ONE. 6 (9): e25161. doi:10.1371/journal.pone.0025161. PMC 3177849Freely accessible. PMID 21957480.
  2. 1 2 Trautner Jürgen, & Geigenmüller Katrin (1987). Tiger beetles, ground beetles. Illustrated key to the Cicindelidae and Carabidae of Europe. TRIOPS Verlag.
  3. 1 2 Basilewsky, P. (1955). Révision des epèces africaines du genre Epomis (Carabidae). Transactions of the Royal Entomological Society of London 107: 95-116.
  4. ↑ Wizen, Gil; Gasith, Avital. "Color variability and body size of larvae of two Epomis species (Coleoptera: Carabidae) in Israel". ZooKeys. 119: 37–52. doi:10.3897/zookeys.119.1451. PMC 3192425Freely accessible. PMID 21998516.
  5. ↑ Shiina, M., and Tachikawa, S. (1988). The life history of Epomis nigricans and its larval stage feeding on toads. Abstracts of the 48th Annual Meeting of the Entomological Society of Japan, p. 35. Nishibaru, Okinawa.
  6. ↑ Tachikawa, S. (1994). Predation on anurans by Epomis nigricans larvae. Amazing Life of Insects, Atlas of the 48th Special Exhibition, Otaru Museum, Otaru.
  7. 1 2 Wizen, Gil; Gasith, Avital. "Predation of amphibians by carabid beetles of the genus Epomis found in the central coastal plain of Israel". ZooKeys. 100: 181–191. doi:10.3897/zookeys.100.1526. PMC 3131015Freely accessible. PMID 21738411.
  8. ↑ Toshiaki, H. (2006). Predation by a carabid beetle (Epomis nigricans) on a juvenile frog (Rana nigromaculata). Bulletin of the Herpetological Society of Japan 2: 99-100.
  9. ↑ http://www.wired.com/2016/01/absurd-creature-of-the-week-this-toad-isnt-eating-a-bug-the-bug-is-eating-it/
  10. ↑ Löbl Ivan, & Aleš Smetana (2010). Catalogue of Palaearctic Coleoptera, Vol.1: Archostemata, Myxophaga, Adephaga. Apollo Books, Stenstrup: 347-356.
  11. ↑ Pietro Brandmayr, Teresa Bonacci, Tullia Zetto Brandmayr (2010): Larval morphology of epomis circumscriptus (Duftschmid 1812) and of first instar E. dejeani, Dejean, 1831 (Coleoptera, Carabidae, Chlaeniini), with morphofunctional remarks. Zootaxa 2388: 49-58.
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