Homaledra Busck, 1900

Hayden, James E., 2021, Two new species of palm-leaf skeletonizers (Lepidoptera: Pterolonchidae: Homaledra Busck), Insecta Mundi 2021 (859), pp. 1-24 : 3-4

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Homaledra Busck, 1900


Homaledra Busck, 1900

Type species. Homaledra heptathalama Busck 1900: 236 , by original designation.

Diagnostic comments. The newly described species are placed in Homaledra Busck because they share numerous characters of adult and immature morphology with H. sabalella and H. heptathalama . Busck (1900) diagnosed Homaledra with external characters and venation in comparison to taxa known at the time. Examined specimens vary more in wing venation than his description indicates (see below), so his diagnosis is minimally useful. Homaledra is currently classified in Gelechioidea: Pterolonchidae Meyrick following the results of Heikkilä et al. (2014), so a proper diagnosis should be made in comparison to other genera in that family. However, that analysis did not include the type species H. heptathalama , which differs from the other species in a few morphological characters that are traditionally deemed significant at higher levels (see Variation below). Thus, the monophyly of Homaledra has not been tested by phylogenetic analysis. The data matrix of Heikkilä et al. (2014, their appendix 3) includes single terminals for most pterolonchid genera, so it would seem straightforward to draw the diagnosis from that. Unfortunately, the dataset includes a few erroneous scorings (L. Kaila, pers. comm. 2020 and pers. obs.) which would make such a diagnosis questionable. Examination of the characters scored by Heikkilä et al. (2014, appendix 2) finds that H. heptathalama and H. sabalella have the same states, except for the conditions (noted below) of the abdominal tergal spine fields, the larval submental pit, sclerotized rings around the SD1 setae, and the A9 SD1 seta.

Homaledra species , including H. heptathalama and the newly described ones, share the following characters. The male forewing retinaculum arises from Sc, not from a spur of Sc. The forewing CuP vein is present and tubular at the distal margin. The hind wing M 1 and M 2 veins are stalked, and the cell is open distally. Abdominal sternum 1–2 has venulae secundae close together, and apophyses are absent. The abdominal tergites have spiniform setae that are in continuous fields or divided in two subdorsal rows; these setae are concentrated on tergites 2–6, with a few on 1 and 7. The gnathos is absent. The transtilla is strongly arched dorsally, the ends arising from the dorsal articulation points of the valvae. A simple juxta is present that lacks lateral lobes. The valvae are simple, without costal or saccular processes or a fibula. The valvae are weakly articulated with the vinculum and are easy to spread apart in dissection and slide-mounting. The wall of the phallus has a narrow sclerite extended most of its length. In the larva, the V setae of T1–T3 are medioposterior of the coxae. The A1 SV group is bisetose. On A9, the D1, D2, and SD1 setae are not in a horizontal line, D1 being anterior of the D2-SD1 line. The female genitalia have one signum that is a round, spiniferous sclerite or a dense field of granules. The female S8 is not longer than other sterna. Adult females of H. heptathalama have not been observed.

Homaledra larvae key out to Stenomatinae in Carter (1998), couplet 68, with setae L1 and L2 on abdominal segment 9 close together. The SV formula is 2, 3, 2, 1, 1 on abdominal segments 1, 2, 7, 8 and 9. In H. sabalella and the species described below, the head has a submental pit ( Fig. 44 View Figures 38–47 : sp), and the abdominal SD1 setae are not surrounded by ringed sclerites. Larvae of H. heptathalama differ in some characters as noted below. The color is uniform pale pink or pale green during development, turning white in preservation ( Fig. 39 View Figures 38–47 ). Prepupal larvae develop bold, dark-pink longitudinal stripes ( Fig. 38, 40 View Figures 38–47 ); this is common to all the species, and no differences in the pattern of stripes was observed among them.

Variation in the genus is as follows. In the adult, a pecten on the antennal scape is present in H. octagonella and those described below but absent in H. sabalella and H. heptathalama . Homaledra heptathalama may have forewing Rs 3 and Rs 4 stalked ( Fig. 37 View Figures 34–37 ), in common with H. sabalella but contrary to Busck’s description. Likewise, the two species described below show variation in venation. Most species have chaetae evenly distributed on the abdominal tergites ( Fig. 11–13 View Figures 11–26 ), but these are divided into two parallel longitudinal rows in H. heptathalama ( Fig. 14 View Figures 11–26 ) and divided on posterior tergites of H. octagonella ( Fig. 15 View Figures 11–26 ). In the larva, a submental pit is present in most species but absent in H. heptathalama . The SD1 seta of A9 varies from normally elongate and seta-like in H. heptathalama , rather reduced in the newly described species, and short, curved, and more hairlike in H. sabalella . Sclerotized rings around the SD1 setae of A1–A8 are present in H. heptathalama but absent in the other species. The SV setae of A3–A6 range from 3 to 5 (rarely 6).

Within Pterolonchidae, Heikkilä et al. (2014) found Homaledra to be related to Syringopais , which includes one species, S. temperatella (Lederer) , in the Near and Middle East. The gnathos is absent in both genera. What Hodges (1998) may have mistaken for a gnathos is either the sclerotized dorsal edge of the tegumen or the dorsally arched transtilla. In contrast, Batrachedra species ( Batrachedridae ) possess a well-developed gnathos, lateral lobes of the juxta, and tergal spines always arranged in two narrow subdorsal rows. Most other pterolonchids possess a gnathos, but a gnathos is absent also in Houdinia flexilissima Hoare, Dugdale, and Watts , a New Zealand species ( Hoare et al. 2006). Homaledra and Syringopais share valvae that are easily separable ( Kemal and Koçak 2015), whereas most other Pterolonchidae have valvae that are relatively immobile and projected posteriad ( Heikkilä et al. 2014). Syringopais shares some of these characters, such as 2 A1 SV setae and presence of a submental pit ( Hodges 1998). Houdinia is described as having an elongate sclerite along the phallus ( Hoare et al. 2006), which all Homaledra species share ( Fig. 22 View Figures 11–26 : ps); a similar structure is known only in Blastobasidae among other gelechioids (M. Metz and D. Adamski, pers. comm. 2020).

Larvae of most Homaledra species feed on the epidermis of leaves of Arecaceae ( Howard et al. 2001) , except that H. octagonella feeds on lichens ( Eiseman 2008). Table 1 presents the host plants on which larvae were collected and moths were reared for the present study. Syringopais larvae are major leafmining pests of wheat and barley, and they also mine in a wide range of herbaceous dicots ( Yefremova et al. 2017). The larvae of Houdinia flexilissima mine the culms of Sporadanthus ferrugineus de Lange, Heenan and Clarkson ( Restionaceae ) ( Hoare et al. 2006). As far as known, a preference for concealed feeding on monocots is unique within Pterolonchidae to Homaledra , Syringopais , and Houdinia , but whether it is a synapomorphy remains to be tested.

A careful morphological comparison and cladistic analysis of all Homaledra species together with S. temperatella , Houdinia flexilissima , and other Pterolonchidae should be done to delimit the genera. If there is any possibility of generic synonymy, Homaledra Busck, 1900 has priority over most pterolonchid genera except Pterolonche Zeller, 1847 .