Sigaus tumidicauda explained

Sigaus tumidicauda is a species of alpine grasshopper, endemic to New Zealand.^[1] Like all of New Zealand sub-alpine and alpine grasshoppers, S. tumidicauda has a 2- or 3-year life cycle. The eggs must "overwinter" before they will hatch. Hoppers are found throughout the year, and adult grasshoppers can be found throughout the New Zealand summer between December and April. This grasshopper is flightless.

Distribution and habitat

Sigaus tumidicauda is known only from the Otago and Southland regions of New Zealand.^[2] It can be found as far south as Cleughearn Peak and as far north as Mount Aurum Sigaus tumidicauda prefers alpine tussock grasslands between 1300mand1700mm (4,300feetand5,600feetm); it can, however, be found as low as 700m (2,300feet) near the Nevis River It is one of three known species of alpine grasshoppers that are found in Fiordland, the other two being Sigaus homerensis and Sigaus takahe.^[3]

Alpinacris tumidicauda is sister to the widespread species Sigaus australis.^[4] The genus Alpinacris included Alpinacris crassicauda previously thought to be sister to A. tumidicauda.^{[5] [6]} Climate change will reduce the current range of this species by 35 - 75%.^[7]

Species description

Sigaus tumidicauda is micropterous (small-winged), with wings measuring between 2mm4mm, making this species flightless like most New Zealand grasshoppers. Male body length is 12mm14mm; female body length is 21mm24mm.

Sigaus tumidicauda was described in 1967 by Robert Sidney Bigelow, in the genus Alpinacris, with a type locality of Obelisk in the Old Man Range A male holotype and paratype are deposited in the Canterbury Museum, Christchurch.

Type information

• Bigelow, R. S. (1967). The Grasshoppers of New Zealand, Their Taxonomy and Distribution. Christchurch: University of Canterbury
• Type locality: Obelisk, Old Man Range, Otago, 1372m (4,501feet)
• Type specimen: Male; 3 December 1963; R. S. Bigelow. Holotype and paratype are deposited in the Canterbury Museum, Christchurch.

Polymorphism

Four colour morphs are known for adult S. tumidicauda: green, olive, dark olive and yellow-brown. The most common colour morph is green, followed by the yellow-brown colour morph.

Notes and References

1. Trewick . Steven A. . Koot . Emily M. . Morgan-Richards . Mary . 2023 . Māwhitiwhiti Aotearoa: Phylogeny and synonymy of the silent alpine grasshopper radiation of New Zealand (Orthoptera: Acrididae) . Zootaxa . 5383 . 2 . 225–241 . 10.11646/zootaxa.5383.2.7 . 1175-5334.
2. Morris SJ. 2002. Distribution and Taxonomic status of New Zealand endangered grasshoppers (Orthoptera: Acrididae). Department of Conservation, Wellington.
3. Morris, S.J. 2003: Two new species of Sigaus from Fiordland, New Zealand (Orthoptera: Acrididae). New Zealand entomologist, 26: 65–74. PDF
4. Koot . Emily M. . Morgan-Richards . Mary . Trewick . Steven A. . 2020 . An alpine grasshopper radiation older than the mountains, on Kā Tiritiri o te Moana (Southern Alps) of Aotearoa (New Zealand) . Molecular Phylogenetics and Evolution . 147 . 106783 . 10.1016/j.ympev.2020.106783 . 1055-7903.
5. Trewick SA, Wallis GP. 2001: Bridging the “beech-gap”: New Zealand invertebrate phylogeography implicates Pleistocene glaciation and pliocene isolation. Evolution 55, No. 11: 2170–2180.
6. Heads, M. 1998. Biogeographic disjunction along the Alpine Fault, New Zealand. Biol. J. Linn. Soc. 63:161–176.
7. Koot . Emily M. . Morgan-Richards . Mary . Trewick . Steven A. . 2022 . Climate change and alpine-adapted insects: modelling environmental envelopes of a grasshopper radiation . Royal Society Open Science . en . 9 . 3 . 10.1098/rsos.211596 . 2054-5703 . 8889178 . 35316945.