Hemiandrus

Hemiandrus electra male

Hemiandrus is a genus of wētā in the family Anostostomatidae. In New Zealand they are known as ground wētā due to their burrowing lifestyle.^[1][2] Hemiandrus wētā are nocturnal,^[3] and reside in these burrows during the day.^[4] Ground wētā seal the entrance of their burrow during the day with a soil plug or door so that their burrow is concealed.^[4] This genus was originally said to be distributed in Australia and New Zealand, however, with recent molecular genetic methods, this is under debate. Ground wētā adults are smaller than other types of wētā, with the unusual trait of having both long and short ovipositors, depending on the species. The name of this genus is said to come from this trait as hemi- mean half and -andrus means male, as the species where the female has a short ovipositor can sometimes be mistaken for a male. This genus has a diverse diet, depending on the species.

Taxonomy

The genus Hemiandrus was originally described by Kjell Ander in 1938.^[5] 10 undescribed species of this genus are said to be in Australia,^[6] however molecular analyses show that the two lineages genetically represent two separate lineages, therefore their Australasian distribution is under debate.^[7] Hemiandrus is however the most species rich genus of the New Zealand Anostostomatidae.^[6]

Morphology

The genus Hemiandrus include the smallest wētā species, with adult individual body size no more than 7 millimetres,^[6] and weighing less than a gram.^[8] The largest Hemiandrus species has a body length of almost 30mm.^[9] These wētā have no tympanum, and instead are able to detect sound through their cuticle, which is adaptive for their underground lifestyle.^[2] Some species in this genus have unusually short ovipositors for Orthopterans, the species with this morphological trait exhibit maternal care,^[4] which is uncommon as it occurs only in five families within the Orthoptera order.^[10]

Diet

The diet of these wētā depends on the species, where H. maculifrons is carnivorous,^[11] H. maia is omnivorous, eating fruit and invertebrates.^[4][12] Other ground wētā species however have been shown to be mainly herbivorous, eating apricots and various grass species.^[13]

Distribution

• Australia (Undescribed species)^[14][15]
• New Zealand - This genus are found throughout the North and South Island, and even on some of the offshore islands of New Zealand.^[6] (See distribution map http://wetageta.massey.ac.nz/Text%20files/groundweta.html). They are found in lowland forests, riverbeds, alpine herb fields, and suburban gardens.^[4] If this genus also occurs in Australia (which there is debate about^[7]), then this is the only non-endemic genus of wētā in New Zealand.^[8]

Behaviour

Several Hemiandrus species have been recorded stridulating, despite lacking the tympanum 'ears' present in other wētā genera. The sounds produced are inaudible to humans and is detected through the cuticle.^[2][16][17] Many of the 'short ovipositor' species have been found to exhibit maternal care with females laying eggs in their burrows and remaining with the eggs and even nymphs while they develop.^[16][4][18]

Hemiandrus in New Zealand

There are approximately 14 undescribed New Zealand species of this genus,^[4] with 19 described species.^[6][19][9] These species of Hemiandrus are eaten by native species such as the wattle birds,^[20] kiwi,^[21] but also by introduced species such as mice,^[22] stoats,^[23] cats,^[24] and hedgehogs.^[25] Of the described species in this genus, half have a restricted range, but most are common and widespread, and are not thought to be endangered (as per the New Zealand Department of Conservation).^[26]

Species

• Hemiandrus bilobatus Ander, 1938
• Hemiandrus brucei Taylor-Smith, Trewick & Morgan-Richards, 2016
• Hemiandrus celaeno Trewick, Taylor-Smith & Morgan-Richards 2020
• Hemiandrus electra Taylor-Smith, Morgan-Richards & Trewick, 2013
• Hemiandrus fiordensis (Salmon, 1950)
• Hemiandrus focalis (Hutton, 1897)
• Hemiandrus jacinda Trewick, 2021^[9]
• Hemiandrus lanceolatus (Walker, 1869)
• Hemiandrus luna Taylor-Smith, Trewick & Morgan-Richards, 2016
• Hemiandrus maculifrons (Walker, 1869)
• Hemiandrus maia Taylor-Smith, Morgan-Richards & Trewick, 2013
• Hemiandrus merope Trewick, Taylor-Smith & Morgan-Richards 2020
• Hemiandrus nitaweta Jewell, 2007
• Hemiandrus nox Taylor-Smith, Trewick & Morgan-Richards, 2016
• Hemiandrus pallitarsis (Walker, 1869)
• Hemiandrus sterope Trewick, Taylor-Smith & Morgan-Richards 2020
• Hemiandrus subantarcticus (Salmon, 1950)
• Hemiandrus superba Jewell, 2007
• Hemiandrus taygete Trewick, Taylor-Smith & Morgan-Richards 2020

Possibly also:

• Hemiandrus monstrosus Salmon, 1950 (listed as valid in the Orthoptera Species File,^[27] as a synonym by other secondary sources^[5])

References