Spider water beetles | |
---|---|
Ancyronyx schillhammeri adult | |
Ancyronyx patrolus larva | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Coleoptera |
Family: | Elmidae |
Subfamily: | Elminae |
Tribe: | Ancyronychini Ganglbauer, 1904 |
Genus: | Ancyronyx Erichson, 1847 |
Type species | |
Macronychus variegatus Germar, 1824 | |
Species | |
See text |
Ancyronyx, commonly known as spider water beetles or spider riffle beetles, is a genus of aquatic riffle beetles from North America, South Asia, China, and Southeast Asia. They are small beetles with extremely long legs ending in strong claws. Both the adults and the larvae are found underwater in the shallow riffles of streams and rivers, clinging to rocks or submerged wood. They feed on algae and decaying wood tissue. The genus contains twenty-one species, eleven of which are endemic to the Philippines.
The genus Ancyronyx was established in 1847 by the German entomologist Wilhelm Ferdinand Erichson based on the type species Macronychus variegatus first described in 1824 by the German coleopterologist Ernst Friedrich Germar. [1] It was regarded as a monotypic species until the French entomologist Antoine Henri Grouvelle described the second species, A. acaroides in 1896. [2] [3] It is the sole member of the tribe Ancyronychini, and is classified under the subfamily Elminae of the riffle beetle family, Elmidae. [3]
Members of Ancyronyx superficially resemble spiders and are aquatic, hence their common name, "spider water beetles". They are typically very small, with an average body length (without legs) of 1 to 2 mm (0.039 to 0.079 in). They are characterized by extremely long legs (longer than the body length). [4] The legs have widely separated coxae, with the procoxae (coxae attached to the prothorax) usually visible dorsally. The legs are tipped with large claws, each with two or three basal teeth. The distal teeth are the largest. [5] The pair of antennae are typically 11-segmented. [6] Most of the species possess brightly colored patterns on their elytra, but not all. [2] [5] [7] The elytra also possess eight to eleven grooves (elytral striae), as well as small depressions (elytral punctures) of varying depth and number. The pronotum possesses a transverse groove and a more or less straight front margin, with pronotal carinae absent or weakly present. [5]
Spider water beetles can be divided into two species groups, based on morphological and ecological adaptation patterns. [8]
Ancyronyx is closely related to the genus Podelmis , but can be distinguished from the latter by the more or less straight and slender last segment of the ovipositor (versus the conical sideways-bent terminal segment of the ovipositor of Podelmis), and the absence of an anterior process on the prosternum. [3]
Like almost all riffle beetles, spider water beetles are aquatic, feeding on algae and decaying wood tissue. [5] [9] However, they can not actively swim. [10] They can be found crawling along or clinging with their claws on boulders or submerged wood in lotic riffles of streams and rivers. [2]
The larvae are exclusively aquatic. They breathe by means of tracheal gills. Spider water beetle adults, like all members of the subfamily Elminae, can also remain indefinitely underwater by means of a plastron, a thin film of gas trapped by hydrophobic bristles (setae) on their body. As the insect breathes, the oxygen concentration in the gas film drops in comparison to the surrounding water, causing new oxygen to diffuse again into the plastron. [10] [11] [12]
Because of their reliance on the plastron for breathing, spider water beetles are restricted to the highly oxygenated environments in moderate to fast-moving permanent running water. [5] They are therefore extremely sensitive to water pollution and are potentially valuable bioindicators for measuring the health of river ecosystems. [4] [13]
Members of the Ancyronyx variegatus species group are mostly found in slightly to moderately polluted (mesosaprobic) rivers, almost always found on submerged wood (with the exception of Ancyronyx yunju which were collected from sand and grass roots). Members of the Ancyronyx patrolus species group, meanwhile, are only found in clean permanent streams, usually among rocks. [3] [5] [8]
Ancyronyx malickyi have been caught using light traps, which might indicate phototaxis. [2]
The genus was previously only known from two species from highly disjunct localities – Ancyronyx variegatus from North America (described in 1824) and Ancyronyx acaroides from Palembang in Sumatra (described in 1896). This strange distribution pattern (and the fact that there were no new specimens of A. acaroides recovered) initially led 20th century specialists to question whether A. acaroides was indeed collected from Sumatra, or whether it was correctly designated to the genus as originally described. However, in 1991, new specimens of A. acaroides were rediscovered from Sumatra by the Austrian coleopterologists Manfred A. Jäch and S. Schödl, confirming its type locality. In addition they also discovered the species in Southeast Asia, including West Malaysia, Sarawak and Bali during 1992 and 1993. The species was also subsequently found in Thailand, Indonesia and the Philippines. [2] Since then, nineteen new species of the genus have been described from Southeast Asia and China. [3] [5] [14] [15]
There are twenty-one species currently classified under Ancyronyx. [11] [16] Eleven of these are endemic to the Philippines, which may indicate that the country is a center of diversity for the genus. [7] [12] Most of the species have highly restricted distributions, often being found in only one island. [16] [17]
Papilio palinurus, the emerald swallowtail, emerald peacock, or green-banded peacock, is a butterfly of the genus Papilio of the family Papilionidae. It is native to Southeast Asia, but is regularly kept in butterfly houses around the world.
Byrrhoidea is a superfamily of beetles belonging to Elateriformia that includes several families which are either aquatic or associated with a semi-aquatic habitat. Other than the superfamily Hydrophiloidea, most of the remaining Polyphagan beetles which are aquatic are in this superfamily.
Silvanidae, "silvan flat bark beetles", is a family of beetles in the superfamily Cucujoidea, consisting of 68 described genera and about 500 described species. The family is represented on all continents except Antarctica, and is most diverse at both the generic and species levels in the Old World tropics.
Copelatus sociennus is a species of diving beetle. It is part of the subfamily Copelatinae in the family Dytiscidae. It was described by J. Balfour-Browne in 1952. The species can be found on Coloane and in Seac Pai Van. It feeds on Nelumbo nucifera.
Dryopidae is a family of beetles, commonly named long-toed water beetles, in the superfamily Byrrhoidea. It was described by Gustaf Johan Billberg in 1820.
Elminae is a subfamily of riffle beetles in the family Elmidae. There are at least 120 genera and more than 1,300 described species in Elminae.
Elmini is a tribe of riffle beetles in the family Elmidae. There are more than 90 genera and 1,200 described species in North America.
Dicranopselaphus is a genus of water-penny beetles in the family Psephenidae. There are over 40 described species in Dicranopselaphus, distributed in Asia and North America.
Phanocerus is a genus of riffle beetles in the family Elmidae. There are about seven described species in Phanocerus.
Zaitzevia is a genus of riffle beetles in the family Elmidae. There are about 19 described species in Zaitzevia. The genus is named after the Russian entomologist Filipp Zaitsev.
Grouvellinus leonardodicaprioi is a species of riffle beetle in the superfamily Byrrhoidea. The beetle was discovered by citizen scientists working with a group of scientists from Taxon Expeditions. G. leonardodicaprioi belongs to the family Elmidae, and it is endemic to Malaysia.
Grouvellinus is a genus of beetle in the family Elmidae. As of 2018, over forty species are recognized, including:
Grouvellinus duplaris is a beetle species from the riffle beetle family. The scientific name of the species was published in 1923 by Champion. It is endemic to India.
Epimetopidae is a family of semi-aquatic beetles belonging to the Hydrophiloidea. They are found in sand and gravel at the edges of streams, rivers and shallow freshwater ponds. These beetles are shorter than half a centimeter long and have a pronotum with a central projection forming a shelf above the head. On the underside of the abdomen only four sternites are visible. There are approximately 72 described species in three genera, Epimetopus which is restricted to the New World, mostly Neotropical, Eupotemus with two Afrotropical species and Eumetopus with some Oriental species. Females carry their eggcases on the underside of the abdomen. The larvae are probably carnivorous based on their mouthparts and likely live in the same habitats as the adults.
Prosopocoilus buddha is a species of stag beetle in the tribe Cladognathini. This Asian species is variable, with several known subspecies and widely distributed from India to Sulawesi.
Erymus gracilis is a species of rove beetle widely spread in Oriental region. It is found throughout China, Sri Lanka, India, Bhutan, Thailand, Malaysia, Laos, Indonesia, Myanmar, and Nepal.
Ancyronyx jaechi is a species of riffle beetle found in Sri Lanka.
Ilamelmis foveicollis, is a species of riffle beetle found in Sri Lanka.
Zaitzeviaria bicolor, is a species of riffle beetle found in Sri Lanka, Philippines and Vietnam.