Ectropis excursaria, Guenée, 1857

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

Ectropis excursaria and Phelotis cognata

The excellent bootstrap support for this clade from both molecular data sets (Figs 10, 12, 15) is reflected in the very low sequence divergence values of 0.0% (28S D2) and 1.2% (EF 1­) for these two Australian boarmiines.

Ectropis Hübner is a large, widespread genus including approximately 23 Australian species. E. excursaria is common and widely distributed in most parts of Australia. The wings of this species are triangular in shape and the adults rest with both wings exposed and closely appressed to the substrate. The brown and black, cryptically coloured and striated wings afford excellent camouflage against bark. The wing striation in the larger female tends to be more diffuse than in the male. Larvae are polyphagous and attack a wide variety of woody and herbaceous plants, both native and introduced. Adults fly throughout the year.

The monotypic P. cognata is also common and widespread in dry sclerophyll forests in southern Australia but is strictly monophagous and feeds on the Australian Native Cherry, Exocarpos cupressiformis Labill. ( McFarland 1988; Common 1993) where its larvae are well camouflaged on the conifer­like foliage. Adults of this species are small with grey and white striated wings that are also strongly appressed to the substrate with both wings fully exposed when adults are in the resting position. In both species the females are distinctly larger than the males

E. excursaria and P. cognata share typically boarmiine features. Both have large eyes, slender bodies a rounded and non­protuberant frons with no basal shelf and antennae that are not pectinate to the apex, although E. excusaria has the much less common quadripectinate condition. There is no distinct apical sensillae chaeticae on the unscaled rami of E. excursaria (see discussion below) but in P. cognata the rami are scaled and terminate in two sensillae chaeticae. Rami in P. cognata originate distally on the antennal segments. Wings are broad and the forewing foveate in both species but areoles are absent in E. excursaria . The two species have a scaly vestiture on the thoracic venter. The male A3 pecten is absent in both species. Interestingly Guest placed excursaria into Phelotis Guest on superficial features in 1887.

The male genitalia (Figs 82, 85) are also typically boarmiine. The uncus is simple, short and wide with a rounded apex and the gnathos short except that in E. excursaria the arms of the gnathos are unattached apically. The valvae are complex with well­developed claspers and have the following features:

—costa well­sclerotised and defined in both, but a free projecting arm in P. cognata ; harpe (clasper) a flap­like, sclerotised projection in both species but setose in E. excursaria ; sacculus, well­sclerotised and defined in both; valvula reduced in P. cognata .

Other features of the male genitalia (Figs 82, 85):

—socii (small) only present in E. excursaria ; vinculum wide and quadrate; saccus slightly extended and pointed posteriorly in P. cognata ; juxta well­developed and extended posteriorly in both species, but larger and bifid in E. excursaria . Note: a bifid juxta was mentioned as being typical of the Alcis Curtis group of Boarmiini by Sato (1984) and is also present in Alsophila aescularia (see above); sparse cristate hair.

The form of the aedeagus is different in the two species (Figs 83, 86). In P. cognata it is short and wide whereas, contrastingly, in E. excursaria it is long and slender. In both species cornuti appear to be sclerotised folds of the tube enclosing the vesica, similar to that found in the Geometrinae (see discussion above).

The female genitalia of E. excursaria (Fig. 84) are differentiated from that of P. cognata (Fig. 87) by the pronounced length of the ovipositor which facilitates the deposition of its fragile eggs into crevices and also wing­like lateral extensions of the lamella postvaginalis.

They share the following features:

—large, sclerotised colliculum; relatively long corpus bursae; a stellate signum; well­sclerotised lamella postvaginalis; membranous, poorly differentiated bursa copulatrix.

The larvae of E. excursaria and P. cognata show some important differences:

— E. excursaria , only, has a granulated integument; SV3 is absent on A 1 in P. cognata only (SV3 is usually present in Ennominae ); P. cognata lacks the fleshy protuberance dorsad of the A2 spiracle that is present in E. excursaria and many other boarmiines ( Sato 1984).

Pupae also show some differences:

—fore­femora only visible in E. excursaria ; dorsal and lateral grooves, although welldeveloped and deep in E. excursaria are absent in P. cognata ; the A5 spiracular furrow is only well­developed in P. cognata ; the cremaster is bifurcate in both, but the apical setae in E. excursaria are long, basally parallel and diverge apically whereas the terminal setae form a T­shape (similar to Alsophila , Archiearis , see above) in P. cognata . However setae are moderately long to long, pro­thoracic spiracles are present, the meta­tibiae are exposed, punctures are small, shallow, densely and randomly distributed on segments A1­ 8, in both species

These boarmiines show many distinct morphological differences in adult, larval and pupal stages despite the high DNA sequence similarity and excellent bootstrap support as sister species. The reason for this discordance may be explained by the following reasons. The highly conserved nature of these genes may prevent separation of some genera, although this is not apparent from the high intrageneric resolution of the archiearine taxa Acalyphes and Dirce using both genes. Accordingly E. excursaria and P. cognata may have undergone rapid divergence that is unable to be resolved by this sequence data. Alternatively the mophological differences may simply be an indication of the structural variation between closely related species.

Other Australian Ectropis species examined here, though similar, showed some heterogeneity in genitalic form. E. excursaria appears to be closest to E. bispinaria as both of these species have socii, a strongly developed bifid juxta, sparse cristate hair, a very long ovipositor and a globular and membranous corpus bursae. E. fractaria and E. despicata , on the other hand, lack socii, the juxta is not bifid, the cristate hair is very welldeveloped and the female ovipositor is short in E. fractaria (females of E. despicata were not available).

Ectropis is a large cosmopolitan genus with 110 species worldwide ( Scoble 1999). Sato (1980, 1984, 1986 and 1992) has recently redefined this genus and restricted the group to species close to the type, the Holarctic E. crepuscularia Denis & Schiffermüller. On the basis of the following comparison E. excursaria has most likely been misplaced in Ectropis .

E. excursaria is superficially similar to other members of the genus but possible significant differences are apparent. The wing venational characters of excursaria are typical apart from the absence of an areole in the forewing. E. excursaria has a quadripectinate antenna instead of the more usual quadri­fasciculate antenna however it is possible that the rami of excursaria are homologous to ciliate fascicles, as they resemble extended forms of fascicles. These structures are less robust than more typical rami, are densely ciliate, unscaled and lack the apical sensilla usually present in pectinate antennae.

Differences in the male genitalia are as follows:

—uncus short and wide, triangular, rather than long and slender; valva complex, as described above, instead of simple; juxta bifid, instead of simple (Fig. 82).

However the female genitalia (Fig. 84) have the following characteristics that Sato nominates as typical of Ectropis :

—a very long and retractile ovipositor; long apophyses; a pair of wing­like lateral extensions to the lamella antevaginalis; semicircular, well­sclerotised lamella postvaginalis; membranous ostium bursae; globular corpus bursae; single, stellate signum; sternite A9 clothed with long hairs.

Sato also defined characteristics unique to Ectropis larvae. First instar larvae have what he termed Ectropis ­ type pigmental pattern: head black, body greyish­black with many white spots, in contrast with the first instar of excursaria that has a yellowish­brown head capsule and a dark­brown body with broad, white dorsal and lateral bands. Of more significance is the presence in Ectropis (sensu Sato 1984) of the so­called SDX1 seta in all instars that is an extra primary seta positioned between D1 and SD1. This seta is absent in excursaria . This extra seta was also noted by McGuffin (1977) as present in the boarmiine genera (sensu Holloway 1994) Melanolophia Hulst and Eufidonia Packard. The L 2 seta is also typically directly ventrad to the spiracle in Ectropis whereas in excursaria it is anteroventrad of the spiracle.

In summary, although E. excursaria resembles its non­Australian congeners superficially and in female genitalic characteristics, differences in the male genitalia and larvae are most likely enough to warrant its placement into another genus. This species may be closer to the Alcis complex of Sato as a defining feature of this group is a bifid juxta. Other features that excursaria shares with this group are type one wing venation (Sc separate to R 1 and R 2) (sensu Sato 1984), granulated larval epidermis and striped firstinstar larvae (e.g. Alcis and Pseuderannis Inoue ). However, unlike excursaria , a signum is absent in this group. P. cognata also has type one wing venation but has a unicolourous light­coloured first instar larva, probably similar to Sato’s immaculate type. This pigmentation is also found in the Alcis complex (e.g. Rikiosato Inoue). In addition, inconsistencies in the morphology of the Australian representatives of Ectropis indicate that a revision of the genus is required to investigate the monophyly of the taxon.