Micrarchus hystriculeus

Micrarchus hystriculeus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Phasmatodea
Family: Phasmatidae
Genus: Micrarchus
Species:
M. hystriculeus
Binomial name
Micrarchus hystriculeus
(Westwood, 1859)

Micrarchus hystriculeus is a species of flightless stick insect (order Phasmatodea) in the family Phasmatidae,[1] and is endemic to New Zealand.[2] It was first described by John Obadiah Westwood in 1859.[3] It is a widespread species of the genus Micrarchus and the only species recorded on North Island.[4] This species is known for its sexual size dimorphism,[5] prolonged mating behaviour,[2] and male-biased sex ratio.[6] It is currently classified as Not Threatened under the New Zealand Threat Classification System.[3]

Description

Micrarchus hystriculeus is apterous (wingless) and exhibit sexual size dimorphism.[5] Adult females are larger than males, exceeding 56 mm in length,[7] with proportionally longer mid and hind legs, which support their larger abdomens.[5] Males are less than 50 mm in length,[7] and are equipped with elongate tong-like claspers armed with a series of black teeth, used to grasp females during copulation.[7] This species is generally small, brown in colour with two rows of spines on their backs and spiky flangers on legs. Their eggs are distinctive and used for species identification.[1][8] Eggs have spine-like setae absent and the capsules are 1.7–2.4 times longer than broad.[7] They have a prominent keel arising steeply and a capitulum (knob-like structure) that is very short, flatly conical, and sharply pointed.[1][7]

Identification features:

Female[7]

  • Cerci distinctly shorter than the anal segment, not reaching the tip of the anal segment
  • Metatarsals of the mid and hind limbs lacking a dorsal lobe
  • Operculum extending up to halfway along the anal segment

Males[7]

  • Claspers forming elongate tong-like pinchers with separate black teeth
  • Dorsal abdominal spines located on the anterior margin of each tergite

Distribution and habitat

This species is widely distributed throughout New Zealand,[2] and is the only member of its genus found on the North Island.[4] It inhabits lowland arboreal habitats and is considered an ecological generalist.[4] Although this species is present in alpine areas, it is less cold-hardy compared to other Micrarchus species.[9]

Biology and ecology

Micrarchus hystriculeus is a plant-feeding stick insect,[5] known to feed on mānuka, ribbonwood and Hoheria.[10] Mating occurs when the male mounts the back of the female and curves his abdomen down and around the female's body, tightly grasping the operculum.[5] This species exhibits prolonged pairing which is thought to function as mate guarding.[11][5] Males compete in grappling contests where males attempt to dislodge males that are mounted on females.[5] Populations have male-biased sex ratio, with unpaired females rarely observed.[6]

Physiological research indicates that this species can survive low temperatures by supercooling but is not entirely freeze tolerant.[9] Compared to the alpine species, this lowland species has a significantly low (<50%) survival rate when ice is present.[9] This species uses a cold tolerance strategy called freeze avoidance, avoiding the internal formation of ice.[9]

Taxonomy and phylogeny

This species name is derived from the Latin word "hystriculeus," meaning “bristly” or "spiny," referring to the insect's spiny body.[7] First described by Westwood in 1859, this species belongs to the order Phasmatodea and is in the family Phasmatidae.[3] The genus Micrarchus contains several species, including an undescribed taxon from the northern area of the South Island of New Zealand, some of which are restricted to alpine habitats.[4]

Molecular phylogenetic analyses show that New Zealand stick insects, including Micrarchus, form a monophyletic radiation derived from a single colonisation event from New Caledonia.[12] Further studies confirmed that all New Zealand Phasmatidae are closely related to each other and to the New Caledonia species.[12]

References

  1. ^ a b c "Phasmida Species File - Micrarchus hystriculeus (Westwood, 1859)". phasmida.speciesfile.org. Retrieved 2025-08-30.
  2. ^ a b c Salmon, J. T. (1991). The Stick Insects of New Zealand. Reed.
  3. ^ a b c Buckley, T. R., Hitchmough, R., Rolfe, J., & Stringer, I. (2014). Conservation status of New Zealand stick insects, 2014. Department of Conservation, Wellington.
  4. ^ a b c d Dunning, L. T., Dennis, A. B., Sinclair, B. J., Newcomb, R. D., & Buckley, T. R. (2014). Divergent transcriptional responses to low temperature among populations of alpine and lowland species of New Zealand stick insects (Micrarchus). Molecular Ecology, 23(2), 271–285.
  5. ^ a b c d e f g Kelly, C. D. (2006). Sexual selection, phenotypic variation, and allometry in genitalic and non-genitalic traits in the sexually size-dimorphic stick insect Micrarchus hystriculeus. Biological Journal of the Linnean Society, 88(4), 607–615.
  6. ^ a b Kelly, C. D. (2008). Male-biased sex ratios and plasticity in post-insemination behaviour in the New Zealand stick insect Micrarchus hystriculeus. Behavioral Ecology and Sociobiology, 62(10), 1547–1555.
  7. ^ a b c d e f g h Jewell, T., & Brock, P. D. (2002). A review of the New Zealand stick insects: new genera and synonymy, keys, and a catalogue. Journal of Orthoptera Research, 11(2), 189–195.
  8. ^ Landcare Research. (2020). Classification and identification of stick insects. https://www.landcareresearch.co.nz/discover-our-research/restoring-ecosystems/plants-invertebrates-fungi-and-bacteria/invertebrate-systematics/stick-insects/classification-and-identification
  9. ^ a b c d Dennis, A. B., Dunning, L. T., Sinclair, B. J., & Buckley, T. R. (2015). Parallel molecular routes to cold adaptation in eight genera of New Zealand stick insects. Scientific Reports, 5, 13965.
  10. ^ Trewick, S; Morgan-Richards, M (2005). Stick Insects: New Zealand Wild. Hong Kong: Reed Publishing. ISBN 1 86948 570 X.
  11. ^ Sivinski, J. (1978). Insemination frequency and sperm competition in the stick insect Diapheromera veliei. Annals of the Entomological Society of America, 71, 373–376.
  12. ^ a b Buckley, T. R., Attanayake, D., Nylander, J. A. A., & Bradler, S. (2009). The phylogenetic placement and biogeographical origins of the New Zealand stick insects (Phasmatodea). Systematic Entomology, 34(2), 207–225.
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