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SUBFAMILY
EUSTROTIINAE |
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Cretonia Walker Type species: platyphaella Walker, Sierra Leone. Synonym: Swinhoea Hampson (type species vegetus Swinhoe, see below). The species have facies typically as in the two Bornean representatives described below, with the forewing rather rectangular, its apex and tornus rather rounded. The forewing is medium to dark blackish brown, and generally darker than the hindwing. It is crossed by a series of blackish fasciae: a curved antemedial, concave distad, that defines a paler basal zone; two much finer, zigzag medial and postmedial fasciae; a broader submarginal that is obtusely angled at one third from the costa. The labial palps are upcurved to well above the head (see also p. 70), with the third segment almost as long as the second. The male antennae are fasciculate. There are no evident phragma lobes to the second abdominal tergite. The male abdomen has the eighth segment unmodified except for shallow, obtusely angled and well separated apodemes to the slightly tapering tergite, which is usually strongly sclerotised around its margin. The genitalia have the tegumen and vinculum long, the latter forming a saccus. The tegumen has a spine arising from it ventrally on each side in a few species including the two from Borneo. The uncus is relatively short and slender, sometimes vestigial. The juxta is variably bifid dorsally. The valves are rectangular or slightly expanding, with a more membranous longitudinal strip separating the costa from the saccular part, and the apical part of the valve appears bifid, the costal part acute and the ventral part shorter, with a rounded cucullar apex that has a corona of setae. At the interior of the cleft between the two parts there is a rugose lobe or more acute process that marks the distal end of the sacculus. The aedeagus vesica has a large, blade-like cornutus in some species. In the female genitalia, the eighth segment forms a complete ring and has long, slender apodemes. There are lateral pockets between the sixth and seventh segments and sometimes a groove above the pleural membrane of the latter. The ostium is broad, sometimes with a bilobed margin, and set at the posterior margin of the seventh sternite, which is sometimes slightly reduced. The ostium leads into a short, sclerotised, conical ductus bursae, and this sclerotisation extends into the base of the corpus bursae. The corpus bursae is short, sausage-like, with increasingly dense scobination in its distal half. Insertion of the ductus seminalis is hard to locate, but probably on the corpus bursae. Placement of this genus in the Eustrotiinae is tentative, given that, as discussed on p. 61, the extension of the subfamily beyond the core Deltote group needs further study. Cretonia shares some features with Maliattha and Hiccoda, but it is not clear whether these are synapomorphies. In the male abdomen, the strengthening of the margin of the eighth tergite is seen also in the other two genera, where a central thinning is surrounded by a rectangular frame. The straight, slender and relatively small uncus is similar in the three genera, though much reduced in Cretonia. It is not clear whether the sclerite extending ventrally from the uncus in Maliattha noted by Ueda (1987) is present in Cretonia, but both genera have a slender subscaphial sclerite. The valves come together narrowly at the base of the sacculus in all the genera and, when mounted in a slide preparation, rest at about 60% or more from the vertical axis. The cucullus is spined with robust setae, and the valve is divided into costal and saccular zones of sclerotisation separated by a weakly sclerotised strip, the cucullus associating with the saccular part. However, where the transtilla extension of the valve costa is slender, angled sharply dorsally near the valve, extending from this angle to arch over the anellus in Maliattha, it is more robust but shorter in Cretonia, terminating at the juxta. The female genitalia show fewer similarities, with the ostium in Maliattha and Hiccoda associated with the interior of the eighth segment and leading into a long, narrow, unsclerotised ductus bursae. The corpus bursae is more delicately rugose or scobinate (sometimes with a small signum), with the ductus seminalis arising from it, often distally. The lateral pouches at the junction of the sixth and seventh segment in Cretonia are probably a modification to receive the spined cucullus, but pouches that are also seen in some Maliattha (e.g. signifera) and members of the Deltote group, such as Protodeltote Ueda, are usually sited more centrally in the pleurite of the seventh segment. The genus contains seven Indo‑Australian and three African species; many of the former were undescribed, as vegetus was discovered to be a species complex during the course of this study, with vegetus itself restricted to India. Two species occur in Borneo that have relatively wide distributions. Only one other, C. brevioripalpus Hulstaert, the most easterly, is named. Brief, diagnostic descriptions of the non‑Bornean species based on male and female genitalia characters are provided here. All are very similar externally, with facies generally as described above. |
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