Amphixystis siccata ( Meyrick, 1910 )

Karisch, Timm, 2022, First records of two non-indigenous tineid species from St Helena Island (Tineioidia: Tineidae), Metamorphosis 33 (1), pp. 68-71 : 68-70

Amphixystis siccata ( Meyrick, 1910)

Material studied (Figs 1, 2, 4, 5)

St Helena Island: Sandy Bay Valley , Ebony Cottage, 3 ♂♂ (1 ♂ barcoding MNVD-11449 -A05, gen. slide 3937, Karisch) 1 ♀ (gen. slide 3944, Karisch) 03.iii.2017, T. Karisch ( SDEI, MNVD); Joan Hill , Man and Horse cliffs, 1 ♀ (barcoding MNVD-11448 -F06) 27.II.2017, T. Karisch ( SDEI). BIN ( BOLD): ADR9744 .

Further observations

St Helena Island: Sapper Way, 1 ex. 12.x.1023, on Hibiscus plant; 1 ex. 26.ii.2014, on Pittosporum viridiflorum Sims ; 1 ex. 15.iii.2014, on Hibiscus plant, L. Fowler; Between Head O’wain Clinic to Burnt Rock road, 1 ex. 25.v.2014, on tree bark, L. Fowler; Burnt Rock , 1 ex. 22.vi.2014, on tree bark; 1 ex. 20.viii.2014, on soil ( Fig. 6 ); 1 ex. 09.i.2015, on house wall, L. Fowler; Millennium Forest , 1 ex. 12.x.2016, on Commidendrum robustum (Roxb.) DC., L. Fowler.

Amphixystis siccata was described by Meyrick (1910) from Mauritius from two specimens. There is a lectotype specimen in the collection of the NHMUK, probably labelled by Robinson, as he published a photo of this specimen with the note “ lectotype ” in his book ( Robinson 2009: fig. 99). Unfortunately this specimen (Fig. 2) has lost the abdomen, so it was not possible to directly compare the genitalia with the specimens from St Helena.

In 2016 M. Bippus published a paper about several Microlepidoptera from La Réunion, neighbouring island to Mauritius. He also found an Amphixystis species, which he identified as A. siccata , and with which he synonymised A. reunionella Guillermet, 2011 , also described from La Réunion.

Because both authors have given illustrations of the moth and the genitalia (male and female in Bippus 2016 – although very small, female in Guillermet 2011) I was able to verify the assumption, that the specimens from St Helena could also belong to A. siccata . Unfortunately, A. siccata was not listed in the database of BOLD and consequently a search for the barcodes does not yield a hit either.

The specimens from St Helena (Figs. 1–3) show the black dots and lines on the forewing, which are typical for A. siccata (Fig. 2). However, there is a slight variability. Sometimes the whitish ground colour of the forewing is more or less grey dusted, when the lines and dots are difficult to discern.

Male genitalia (Figs 4a, b)

With the characteristic, strongly sclerotised socii, the comparatively long and narrow valva and a projecting sacculus, in this species forming a curved tooth; saccus very long, rod-like, as described in Robinson & Tuck (1997) as typical for Amphixystis species, and illustrated in Bippus (2016) for A. siccata . The stout aedeagus (Fig. 4b) also matches the illustration in Bippus (2016).

Female genitalia (Figs 5a, b)

The main character of the female genitalia of A. siccata is the broad signum with the two pointed, curved, manta raylike lateral wings and the clasp-like curved sclerotisation at the beginning of the corpus bursae (fig. 5 b).

Distribution

As far as known A. siccata is distributed on the islands of La Réunion and Mauritius in the Indian Ocean East of Madagascar. It was beyond the scope of this paper to study all described species, but it is possible, that the very similar A. polystrigella ( Legrand, 1965) from Mahé Island ( Seychelles) is also synonymous with A. siccata .

Host plants

Not much is known about the host plants of Amphixystis in the Aethiopis, but Robinson (2009) mentioned, that A. polystrigella was bred from decaying husks of Lodoicea maldivica (J. F. Gmel.) Pers. (Coco de Mer, Palmae) and A. anchiala (Meyrick, 1909) ( Madagascar) was reared from dead stems of Euphorbia resinifera O. Berg. Therefore it may be assumed that the larvae of A. siccata also feed on decaying plant material. However, the answer to the question “how could A. siccata have reached the island of St Helena?” remains open.

Habitat

The records of A. siccata on St Helena are mainly from man-made habitats, such as plantations and gardens, and the ruderal tertiary vegetation following the destruction of secondary habitats by grazing goats. The species is established in areas at low and middle altitude.

Figures

Figure 6 – Live photo A. siccata, Burnt Rock, on soil (L. Fowler).