Theclinesthes onycha

Theclinesthes onycha (Hewitson, [1865])
Cycad Blue
(previously known as Utica onycha)
POLYOMMATINI, POLYOMMATINAE, LYCAENIDAE, PAPILIONOIDEA

Don Herbison-Evans
(donherbisonevans@yahoo.com)
and
Stella Crossley

Theclinesthes onycha
(Photo: courtesy of Don Ashton, Mudgeeraba, Queensland)

The caterpillars of this species are initially green with a dark reddish dorsal line edged in paler green. Later instars are brown. The species is unique in that it is the only Australian butterfly caterpillar that feeds on Cycads, namely species from the families CYCADACEAE and ZAMIACEAE such as :

Ceratozamia robusta,

Cycas media,

Cycas megacarpa,

Macrozamia pauli-guilielmi, and

Macrozamia spiralis.

The caterpillars eat the young shoots and stems, feeding mainly nocturnally. By day they hide in the base of the plant or under the fronds. The caterpillars are often attended by various species of green or black ants.

male
(Photo: courtesy of CSIRO/BIO Photography Group, Centre for Biodiversity Genomics, University of Guelph)

The adult butterflies are brown with a lilac or purple sheen. There is often an obscure arc of dark spots around each hindwing margin. The undersides are brown with pale wiggly lines. The hindwings each have a little tail near the tornus, and one or two orange-edged black spots on each hindwing beside the tail. The butterflies have a wingspan of about 3 cms.

female
(Photo: courtesy of CSIRO/BIO Photography Group, Centre for Biodiversity Genomics, University of Guelph)

Males are reported to fly around hilltops, while the females can more often be seen around the foodplant. The species occurs in Australia and shows much variation, especially between seasons.

egg, magnified
(Photo: courtesy of Ken Walker, Millmerran, Queensland)

Eggs are very off-white, toroidal, and covered in a diamond-shaped lattice of ribs. The eggs have a diameter of about 0.6 mm. They are laid singly on young growth of a foodplant.

(Photo: Don Herbison-Evans, Mackay, Queensland)

Two subspecies have been recognised :

capricornia Sibatani & Grund, 1978, in the Northern Territory and the northern half of Queensland, and

onycha in southern Queensland and New South Wales.

There is some evidence that subspecies have different foodplant preferences, with subspecies onycha preferring Macrozamia species, and subspecies capricornia preferring Cycas species.

underside
(Photo: courtesy of Nick Monaghan, Mount Coolum, Queensland)

Further reading :

Michael F. Braby,
Butterflies of Australia,
CSIRO Publishing, Melbourne 2000, vol. 2, pp. 805-807.

Jak Guyomar,
Letter: Theclinesthes onycha
Butterflies and Other Invertebrates Club,
Metamorphosis Australia,
Issue 52 (March 2009), p. 30.

William Chapman Hewitson,
Utica,
Illustrations of Diurnal Lepidoptera, Lycaenidae,
London, Volume 2 (1865), p. 56, and also Plate 24, figs. 11-12.

John T. St. L. Moss,
The Mysterious Cycad Blue Butterfly, Theclinesthes onycha (Hewitson [1865])
Butterflies and Other Invertebrates Club,
Metamorphosis Australia,
Issue 53 (June 2009), pp. 11-14.

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(updated 22 March 2011, 18 November 2013, 11 August 2020)