Oristicta Tillyard, 1913

Burwell, Chris J., 2017, A second species of Oristicta Tillyard (Odonata: Isostictidae), Zootaxa 4323 (1), pp. 83-95 : 84

Genus Oristicta Tillyard, 1913

In the diagnosis of Oristicta Tillyard (1913) included the following crucial information ( Figs 1–3 ):

Basal postcostal nervule (=Ac) situated between the levels of the two antenodals, but closer to the first (=Ax1) than to the second.

Inferior sector of triangle (=1A) absent; superior sector (=CuP) terminating at level of nodus, forming only one cell beyond quadrilateral.

Median sector (=R4) arising after the nodal crossvein (=Sn).

Type species: Oristicta filicicola Tillyard, 1913 .

In the diagnosis of Phasmosticta (considered as a junior synonym of Oristicta , see below) Lieftinck (1951) included the following crucial information ( Figs 14–15 ):

Ac situated distinctly proximal to the level of Ax 1 in forewing, at that level in hindwing.

Cu1 (=CuP) one cell long, entering the wing border just beyond the first crossvein following the quadrilateral, which itself is situated before level of subnodus (=Sn).

Cu2 (=1A) absent.

First cross nerve between M3 and M4 (=R4) not in alignment with the subnodus, but situated far beyond that level.

Type species: Phasmosticta interposita Lieftinck, 1951 .

According to Lieftinck (1951) Phasmosticta can be at once distinguished from Oristicta by the more basal position of Ac, the smaller amount of petiolation and different shape of the wings, the non-aberrant pterostigma, and by the different colour scheme of the body. Watson (1974), however, regarded P. interposita as a junior synonym of O. filicicola and he expanded on this in Watson et al. (1991). This view was accepted by Houston and Watson (1988), Watson et al. (1991), Watson (1994), Theischinger & Hawking (2006) and Theischinger & Endersby (2009).

Figures

FIGURES 1 – 4. Oristicta filicicola Tillyard, male: (1 – 3) modified from Tillyard (1913): (1) hindwing; (2 – 3) anal appendages: (2) right side, dorsal; (3) lateral; (4) posterior lobe of pronotum, dorsal: (a) from Iron Range; (b) from Lizard Island nr Cooktown.

FIGURES 13 – 15. Phasmosticta interposita Lieftinck, Holotype male: (13) Habitus, lateral. Photo by J Van Tol; (14 – 15) Modified from Lieftinck (1951): (14) wings; (15) anal appendages, lateral.