Sterrhinae (McGuffin, 1987)

Young, Catherine J., 2006, Molecular relationships of the Australian Ennominae (Lepidoptera: Geometridae) and implications for the phylogeny of the Geometridae from molecular and morphological data, Zootaxa 1264 (1), pp. 1-147 : 1-147

Sterrhinae

Monophyly of the Sterrhinae

The Sterrhinae are represented by only two species from two tribes, the Palaearctic species Idaea aversata (Sterrhini) and Scopula ornata (Scopulini) . In this analysis (28S D2) the monophyly of this clade is extremely well supported by the molecular data (Fig. 10), the morphological analysis (Fig. 16) and also the combined morphological and molecular analysis (Fig. 17). In this study (28S D2) the Sterrhinae are also supported as a sister group to (the Geometridae minus the Larentiinae ) (Fig. 10). Both these relationships were also recovered by the study by Abraham et al. (2001). However, in the latter study, Idaea Treitschke is nested within Scopula Schrank. Sequence divergence between the two species was 10.1% (Appendix 6).

The Sterrhinae are difficult to define on morphological characters. However most sterrhines are small moths with wings bearing numerous wavy fasciae and prominent discal spots on all wings. A pale spot often surrounds the discal spot on the hindwing (Holloway 1998; Minet & Scoble 1999). Eggs are laid flat and deposited loosely (a characteristic of herbaceous feeders) ( McFarland 1988). Larvae have a long slender body with two pairs of prolegs and sometimes a bilobed head ( Scoble 1995). The sterrhine pupa is generally distinguished from that of other subfamilies by the absence of setae on A1 and A9, the possession of a non­tapering mesothoracic leg and the prothoracic leg originating further caudad than in other geometrids ( Nakamura 1994). Interestingly an unusual record of exposed pupae in the Geometridae was recorded from two Australian species of the large Indoaustralian sterrhine genus, Perixera obrinaria Guenée and P. pallida Moore. These pupae were attached to the food plant by a central silken girdle in the characteristically butterfly­like manner perhaps further indicating relatively primitive status for this subfamily ( Common 1986).

Adults of S. ornata were unavailable for examination; however the characters shared by I. aversata and the Australian sterrhine Scopula perlata are as follows:

—fasciculate antennae; Sc + R 1 and Rs of hindwing fused near inner end of cell for less than ¼ of its length and then immediately diverging; epiphysis originating in upper half of fore­tibia; no spurs on hind­tibiae; hind­tibiae very swollen (width 0.16–0.18 x length) and with hair pencil but no groove as is present in other Geometridae possessing this character [this feature was also noted by Hashimoto (1992) as being particularly welldeveloped in I. biselata Hüfnagel and S. ignobilis Warren and that the primary function of the hind legs is in the secretion of the male pheromone and not locomotion]; bi­lobed papillae anales [Holloway (1998) commented that this was a tribal apomorphy for Scopulini )]; larvae feed on herbaceous plants.

The modification of the ovipositor was present in both genera of the Sterrhinae [clearly illustrated for Idaea in Fig. 237 (Holloway 1998)] and also the Drepaninae in this study (data not shown). The homology of this structure in the different families is uncertain. Certainly the position of the lobes is similar, however in the Drepaninae they are relatively larger (not illustrated).

Egg characters also support a close relationship between Scopula (Fig. 22) and Idaea ( Salkeld 1983) . Eggs of both species are characterised by the columnar arrangement of the cells and the prominent lengthwise ridges on the chorion.

The modification of the ovipositor lobes, unusual pupal attachment and also lengthwise ridges on the eggs support the relatively basally derived position of this subfamily.