Sigaus is a genus of grasshoppers in the tribe Catantopini that is endemic to New Zealand. All but one Sigaus species is endemic to the South Island: Sigaus piliferus is the only North Island representative and is the type species. Most species in this genus are restricted to alpine habitats. All are wingless and make no sounds.
There are thirteen species in the genus all are adapted to cold conditions, and many are coloured for camouflage against rocky ground.[1] [2] The largest species Sigaus villosus can reach 48mm (body length of adult female). The smallest species Sigaus minutus and S. childi are threatened with extinction.[3]
The taxonomy of New Zealand endemic grasshoppers was substantially revised by Bigelow in 1967, based mostly on female genitalia, and again in 2023 using genetic data.[4] The New Zealand radiation of cold-adapted grasshoppers is monophyletic but neither genetics nor morphology resolve distinctive genera, therefore it was suggested that all thirteen species be placed in the genus Sigaus. The genus Sigaus is distinguished from other Acrididae as flightless, silent acridids with short tegmina, crypsis colouration and endemic to New Zealand. Each species has distinctive pronotum shape and structures of the internal male genitalia: the epiphallus lophi are saddle-like in shape with the mesal protuberance of the lophus having a smooth, rounded outline.[5] The genus is monophyletic and sister to grasshoppers from Tasmania, Australia.[6]
| Sigaus australis | Sigaus campestris | Sigaus childi | Sigaus homerensis | Sigaus minutus | Sigaus piliferus | Sigaus obelisci | Sigaus takahe | Sigaus villosus | ||
|---|---|---|---|---|---|---|---|---|---|---|
| Photograph | ||||||||||
| Elevation[7] | 1,300–1,700 m (4,300–5,600 ft) | 400–1,500 m (1,300–4,900 ft) | 200–500 m (660–1,600 ft) | 900–1,000 m (3,000–3,300 ft) | 300–800 m (980–2,600 ft) | 1,600–1,800 m (5,200–5,900 ft) | 1,000–1,400 m (5,900–6,900 ft) | 1,800–2,100 m (–6,900 ft) | ||
| Described[8] | 1897[9] Hutton | 1897 Hutton | 1999[10] Jamieson | 2003[11] Morris | 1967[12] Bigelow | 1897 Hutton | 1967 Bigelow | 2003 Morris | 1950[13] Salmon | |
| Habitat[14] | Tussock grasslands | Dry rocky hillsides/ tussock grasslands | Dry rocky hillsides | Tussock grasslands | Fluvial outwash | Tussock grasslands | Alpine lichen fields | Tussock grasslands | Scree | |
| Polymorphism[15] | Highly cryptic | Highly cryptic | Highly cryptic | 2 | Highly cryptic | 2 | Highly cryptic | 1 | ||
| Regions | Canterbury Otago | Canterbury Otago Southland | Otago | Southland | Canterbury | Waikato Gisborne Hawke's Bay Manawatū-Whanganui Wellington | Otago | Southland | Canterbury | |
| Size[16] | Medium | Medium/large | Medium | Medium | Very small | Large | Large | Medium | Large | |
| Status[17] | Not threatened | Not threatened | Nationally Critical | Range Restricted | Nationally Endangered | Not threatened | Range Restricted | Range Restricted | Not threatened | |
| Wings[18] | Micropterous 2–3 mm | Micropterous 2–3 mm | Micropterous 1–2 mm | Micropterous 2–3 mm | Micropterous 1 mm | Micropterous 3–4 mm | Micropterous 3–4 mm | Micropterous 2–4 mm |