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Rivula
Guenee
Type species:
sericealis
Scopoli, Slovenia.
Synonyms: Cholimma Walker (type species leucanioides Walker = aequalis Walker); Motina Walker (type species aequalis Walker, see below); Pasira Moore (type species ochracea Moore, India) praeocc.; Plotheia Walker (type species innotabilis Walker, see below) praeocc.; Paurosceles Turner (type species geminipuncta Turner, Australia, = everta Swinhoe); Rhazunda Walker (type species distributa Walker, Venezuela); Rivulana Bethune-Baker (type species ochrea Bethune-Baker, Angola); Thopelia Nye (replacement name for Plotheia).
The extent and cohesion of this genus requires further investigation, but the Bornean species could mostly be considered to be congeneric, as there are sufficient unusual features shown by a good number of these species to indicate that a natural group is involved, though the characters do not coincide exactly across the range of species, nor are there data on early stages for all of them.
However, the larval features mentioned in the previous section, and the mode of pupation described for several species in the sections below are common to all those species where the life history is known. The early stages of the Palearctic type species are described briefly by Bretherton et al. (1983).
The males usually have hair-pencils on the mid-tibia, and these may interact with a diverse array of corematous structures on the fifth and sixth sternites. However, not all species have these features, including the generic type species, that of Rivulana and those of Paurosceles, Cholimma, Motina and Pasira (a junior homonym), the last three being represented by aequalis Walker in Borneo. The only other Bornean species to lack these structures is curvifera Walker. All species have the eighth segment of the framed corematous type, again with some quite striking modifications as illustrated. The taxa without central abdominal ornamentation often have the eighth sternite more developed, such as by a dense mop of scales from the coremata. The genitalia usually have a narrow capsule with elongate, narrow valves that mostly lack processes, and have their bases well embedded in the upper part of the saccus. The juxta is broad, plate-like, and there is a transtilla immediately above it. The aedeagus is relatively large, and the vesica is generally coarsely scobinate over much or all of its area.
The female genitalia are diverse in structure, but the corpus bursae usually contains a signum or a pair of signa. These signa are often robust, tongue-like or trident-like in form and occur in the distal bulb of the bursa.
The species vary in wing facies, but many have forewings that are fawn, brown or greyish brown with a darker discal patch and only faint fasciation, the postmedial, when evident, often being sharply angled subcostally. Others have blocks of dark marking basally or longitudinally, and there is a group with white spotting on dark brown. The male antennae are usually ciliate. The labial palps extend forwards or are curved upwards to just above the level of the head, with a deep, rectangular or club-like second segment and a very short third one.
Amongst the generic synonyms listed above, Poole (1989) excluded Thophelia as a good genus, but its type species shows the features noted above. Rivula is most diverse in the Oriental tropics, moderately so in Australasia (see Robinson (1975) and Holloway (1979) for the south-west Pacific) and possibly Africa, but its extent in the New World is unclear. Six species of Rivula are listed in Nielsen et al. (1996) for Australia.
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