''Arixenia esau'' is a species of earwig in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Arixenia ''Arixenia'' is a genus of earwigs, one of only two genera in the family Arixeniidae, and contains two species. See also * Earwig Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the ...

(sister to ''

Arixenia camura ''Arixenia camura'' is a species of earwig Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincer ...

''). It is in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Arixeniidae Arixeniidae is a family of earwigs in the suborder Neodermaptera. Arixeniidae was formerly considered a suborder, Arixeniina, but was reduced in rank to family and included in the new suborder Neodermaptera. Arixeniidae is represented by two gene ...

, a group composed solely of ectoparasitic earwigs. Like most other species in Arixeniidae, ''A. esau'' is found in the tropics of

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

and

Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...

and has only been collected on the island of

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and eas ...

. The species is heavily associated with its host the hairless bat ( Cheiromeles torquatus) and is most commonly collected from the fur of these bats and from caves inhabited by them. Arixenia esau is a rare species and has only been observed infrequently in its natural habitat.

Description

This species was described by the entomologist Karl Jordan in 1909, when it was recorded as living within the brood pouches of hairless bats. Like the related species Xeniaria jacobsoni, ''A. esau'' females are much larger in size than the males. ''A. esau'' is easily contrasted from other members of the order

Dermaptera Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincers on their abdomen, and membranous wings folded ...

by its minute cerci and full body covering of sensory hairs giving adults a mottled appearance. Like all species in the Arixeniidae family, ''A. esau'' is wingless and blind. Nymphs and adults are a deep yellowish-brown color, although adults have darker abdominal tergites. The head is prognathous and heart-shaped, broad, and wide. The eyes are small and oval shaped, containing 50 to 65 facets in the males and between 60 and 90 in the females. Antennae have 14 segments and are inserted laterally on the head. Mouthparts are smaller than in other Arixeniidae species, the

mandibles In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

bearing 3 apical teeth with small maxilla. The

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on ea ...

of the thorax is curved posteriorly and exceeds the mesonotum significantly in length. The tarsal claws are well developed to enable gripping on the fur of hosts.

Biology and life history

This species was originally described as ectoparasitic to its bat hosts, but this relationship has been revised and it is currently understood that the earwigs are not parasitic as they do not harm the bats in the process of feeding off of dead skin and bodily excretions. As the earwigs are blind and flightless, they spend their entire lives within the caves inhabited by their hosts. Like some other earwig species ''Arixenia esau'' is

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

, giving birth to live offspring that develop in a uterus. This feature has evolved twice within the Dermapteran order, in the groups

Hemimeridae Hemimeridae is a family of earwigs in the suborder Neodermaptera. Hemimeridae was formerly considered a suborder, Hemimerina, but was reduced in rank to family and included in the new suborder Neodermaptera. Hemimeridae is represented by two gen ...

and Arixeniidae. Arixenia esau has a unique respiratory system to support larval development within the reproductive tract of the mother. An extensive tracheal system within the mothers body delivers oxygen through the respiratory pigment

hemocyanin Hemocyanins (also spelled haemocyanins and abbreviated Hc) are proteins that transport oxygen throughout the bodies of some invertebrate animals. These metalloproteins contain two copper atoms that reversibly bind a single oxygen molecule (O2) ...

which is found in the fatty tissue of the larva while a placenta-like organ growing out of the larval abdomen mediates this gas exchange.

Association with bat fleas

This species is associated with the bat fleas '' Lagaropsylla signata'' and '' Lagaropsylla turba'', whose survival depends on easy access to hosts via riding on the earwig's body. This association is the only known example of a true phoreteic relationship between bat fleas and other insects. The hairs on the earwigs body make them ideal vectors for the fleas, who would otherwise remain trapped on the cave floors unable to reach the roosting bats.

References

External links

An example of a female ''Arixenia esau'' from the Australian National Insect Collection
!-- If the link breaks, please use the archived version at https://www.webcitation.org/5fz0GZbVb. --> * {{Taxonbar, from=Q669721 Arixeniina Insects described in 1909 Insects of Asia Parasites of bats Taxa named by Karl Jordan Insects of Borneo