INTRODUCTION

Subfamilies of the Noctuidae included in this part of The Moths of Borneo are often referred to as the Trifinae because of the condition of the hindwing venation they mostly share: loss of vein M2 such that the posterior angle of the cell has only three veins arising from it, M3, CuA1 and CuA2. The group would appear to be a natural one, though classification of subfamilies within it is not satisfactory.

The trifines are of great interest for several reasons. The most important is that they have been highly successful at moving into, and diversifying within, open habitats, feeding on herbaceous plants. Many are highly dispersive, sometimes migratory, being quick to colonise ephemeral, weedy habitats, the early stages in vegetational succession. They form a major component of the faunas of isolated tropical islands, such as those of Polynesia, and the major component of faunas at high latitudes.

This versatility has brought many of them into conflict with man. Some of the most devastating pests in tropical agriculture are trifine noctuids: cutworms, armyworms, earworms and stem borers.

Their predominance at high latitutes is reflected in the tropics at high altitudes, where they are the predominant noctuid group. In Borneo most of the Noctuidae found only on G. Kinabalu are trifines, including the only noctuid of the small summit element, Diarsia barlowi Holloway.

The Trifinae as a natural group
Kitching (1984) suggested that the trifine subfamilies, together with the pantheinae, were held together on rather dubious grounds mostly the loss of vein M2 in the hindwing (Figure 1). Even this venation character is not seen in all currently recognised trifines. M2 is present in the Pantheinae and in genera of the Amphipyrini such as Bagada Walker, Condica Walker, Callopistria Hubner, Dipterygina Sugi, Lignispalta Gen. n., Mudaria Moore, and Yula Bethune-Baker.

Nevertheless there are other features that suggest that the majority of trifine genera do form a natural group and at some subgroups can be recognised.

The most important feature is the pair of hair pencils located in the base of the male abdomen. These have been discussed in detail by Birch (1972, 1979) and arise from the anterior of the basal sternite as sclerotised bands (the levers) that extend anteriorly lateral to the sternite to terminate each in a plate from which arises the scent pencil, a tuft of long hair-scales. Associated with each lever is a small glandular structure, Stobbe's gland. The scent pencils are enfolded in elongated pouches set laterally in more posterior sternites, and are only displayed during courtship. They are illustrated in Figs. 2-7. The complexity of this structure is such that it provides a strong synapomorphy for trifine groups. It is found in Agaristinae, Hadeninae, Noctuinae, Cuculliinae, Amphipyrinae, Heliothinae and Stiriinae. It is not found in the Acronictinae, and is only seen in Elydnodes Hampson of the Pantheinae, a probably polyphyletic group (Holloway, 1985).

Figure 1. Quadrifine (Stictoptera, left) and trifine (Spodoptera, right) hindwing venation. The arrow indicates vein M2 or the fold marking its position.

Several or many genera of each of these subfamilies lack the basal hair pencils, and they may be variably present within a genus (e.g. Mythimna Ochsenheimer). It is therefore difficult to assess whether the generally plesiomorphic Amphipyrini genera without them never had them or have secondarily lost them.

The next feature of interest is the ornamentation of the bursa by longitudinal, scobinate, band-like signa, often up to four in number, very rarely more. If this is considered apomorphic to the fine, general scobination seen in the bursa in many Amphipyrini, Acronictinae and Agaristinae, it serves to group together the Noctuinae, Hadeninae, Cuculliinae, Apameini (of the Amphipyrinae) and the Heliothinae and Stiriinae. In many genera of these they are lost or otherwise modified, but occur with sufficient frequency to suggest that these subfamilies might form a natural group.

Matthews (1988) discusses in detail the probable sister-relationship between the Stiriinae and Heliothinae. The larvae have a characteristically spiny skin and are flower, seed and fruit feeders in both groups. The harpe arises simply from the sacculus in a rather basal position as in Amphipyrini, Acronictinae and Agaristinae.

The Noctuinae, Hadeninae, Cuculliinae and Apameini mostly show variations on a different type of harpe. It occurs more distally on the valve and more towards the costa, and overlaps a process from the costa that extends across the interior lamina of the valve towards the ventral margin, often making the harpe appear bifid or trifid. The feature is seen most clearly in Diarsia Hubner (Noctuinae), Mythimna (Hadeninae) and Apamea Ochsenheimer (Apameini). It is often associated with development of the valve apex into a cucullus, a paddle-shaped structure, fringed distally by the corona and often bearing further stout spines on the interior. The groups showing this feature will be referred to subsequently as the 'higher trifines'.

Other features of adult morphology which might repay investigation are: the presence of a coronal row of stout setae at the valve apex, seen widely in trifine groups but probably absent from quadrifine groups; development of a strongly setose peniculus (the ventral part of each side of the tegumen); the presence of lateral rods to the male eighth sternite, seen widely in all except the higher trifines, but not surveyed in the quadrifines. In the higher trifines there is a tendency for the basal sternite of the abdomen to become wider and shorter (see Figs. 11, 12 compared with Figs 13, 14, 18), with the apodemes more widely separated. The aedeagus vesica is, in general, very much longer in the groups with the apomorphic state of the female bursa, and is correlated with marked development of the appendix bursae. In most higher trifines and a few 'lower' ones (e.g. Condica Walker, Sasunaga Moore) the male eighth tergite has two longitudinal bands of sclerotisation that are fused anteriorly, thence diverge and broaden posteriorly to be bridged distally by a broad, rather diffuse, transverse zone of sclerotisation to form a roughly triangular structure. In the eighth sternite coremata are variably present in lower trifines, but in higher trifines there is a trend towards loss of lateral rods, and, just posterior to the anterior margin, occurrence of a transverse band of long, hairlike setae.

Larval morphology may provide a means of testing these indications of relationship within the trifines; it is interesting to note that the only published attempt to order the characteristics of both tropical and temperate larvae, possible in India (Gardner, 1946-1948), led to an arrangement that was very much at odds with the Hampsonian classification then accepted (Kitching, 1984; 191). Subsequent work on larvae, reviewed by Kitching, has tended to identify the trifines as a unit but has varied widely in recognition of groupings within them.

Sugi (1987) included members of the previously quadrifine Belciana Walker complex of genera in the Acronictinae on the basis of larval features. The relationship of the more plesiomorphic trifines with such quadrifine genera requires further investigation.

Host-plant specialisations and economic importance.

It is generally true that herbaceous-feeding larvae are predominant in the higher trifines and Heliothinae and Stiriinae, exceptions being mainly in the Hadeninae and Cuculliinae, whereas in the more plesiomorphic trifines arboreal feeding is predominant.

Within the higher trifines there are three major groupings of grassfeeders which include very many serious pests of cereal crops and pastures, both tropical and temperate. In the Hadeninae there is the diverse Mythimna group, and in the Apameini the complex that includes Apamea and both temperate and tropical stem-boring groups; these are discussed in more detail later. In both cases the ovipositor lobes are distinctively modified to enable eggs to be inserted within the leaf sheath, though the modification is very different in each group. The third group of grass-feeders is found in the genus Spodoptera Guenee along with a number of dicotyledonous feeders, mostly polyphagous but with a few rather specialist taxa. Unlike the first two groups, there are no strong indications that the graminaceous taxa form a natural assemblage (I.J. Kitching, pers. comm.).

Most of the other herbaceous-feeding genera found in Borneo are polyphagous, exceptions being Actinotia Hubner on Hypericum (Guttiferae) and Condica Walker on Compositae.

The genus Callopistria Hubner is unusual in being restricted to ferns as host-plants, a restriction seen also amongst the trifines in the African hadenine genus Nyodes Laporte and the Old World tropical and subtropical  genus Appana Moore that occurs in Peninsular Malaysia and Sulawesi but has not been recorded from Borneo.

Amongst the arboreal feeders there are more specialist genera. In the Acronictinae the genera Craniophora Snellen, Thalatha Walker and Thalathoides Gen. n. all feed on the family Oleaceae. Agaristinae often show a strong preference for Vitaceae. Dipterygina Sugi is restricted to Callicarpa (Verbenaceae), and Sasunaga Moore and allied genera specialise in the Rhamnaceae. Tiliaceae, Sterculiaceae and Malvaceae are favoured by Chasmina Walker and possibly Dyrzela Walker. Prometopus species may be conifer feeders.

A most interesting specialisation is shown by the genus Mudaria Moore where the larvae are borers in fruits of Bombacaceae, attacking durian and kapok, and thus being of economic importance. This genus is a possible sister-taxon to Chasmina, and so the combined grouping is specialist on Malvales; Malvaceae and Bombacaceae have been treated as a single family in the past.

Most species of economic importance are found amongst the herbaceous feeders. Those attacking Gramineae have already been mentioned, but the genus Spodoptera also includes a number of highly polyphagous species that attack vegetable crops, a species that is used for control of water weeds in Thailand, and a rather bizarre indirect pest of fisheries in Fiji!

The Noctuinae contain a number of cutworm genera that include pests in temperate regions. In the tropics their species tend to be montane but could become more serious pests if there were an expansion of cultivation of temperate vegetation at high altitudes. Agrotis Ochsenheimer species are of particular importance in this respect.

The Bornean Heliothinae number only two but both are known pests, attacking the seeds and fruits of a number of crops such as maize, solanaceous fruits, pulses, citrus and cucurbits.

The majority of pests in the Hadeninae is in the genus Mythimna as discussed above, but the polyphagous larvae of Tiracola Moore species have also been recorded as defoliating a large number of plants of economic importance.

The Amphipyrinae include Spodoptera and the complex of graminaceous stem-borers already referred to. The latter are far less diverse than in Africa, perhaps reflecting the greater extent of natural grasslands in Africa. The genus Athetis Hubner contains a number of generalist herbaceous feeders that are often common in agricultural ecosystems. Condica Walker, a specialist genus on Compositae, contains pest species that attack safflower in India and are frequently encountered where weedy compositae are common.

The non-pest species found in abundance in agricultural systems feeding on weeds may be of importance both for weed control and as reservoirs for populations of non-specialist parasitoids and other natural enemies of pests.

Ecology and geography.
Trifine noctuid species in the Oriental tropics fall into three main categories:species of lowland rainforest; species of early successional and agricultural systems; montane species (Holloway, Robinson & Tuck, in press).

Most of the arboreal feeding 'lower trifines' fall into the first category. The genera are, with a few exceptions such as Craniophora Snellen, entirely tropical, mostly found only in the Indo-Australian tropics and a few restricted to the Oriental tropics (e.g. Eulepa Walker) or most diverse there (Dyrzela Walker, Mudaria Moore, Bagada Walker).

The open habitat species of the lowlands are more cosmopolitan, occurring in the Neotropics also, such as Spodoptera, Condica, Tiracola, Athetis and Callopistria Hubner. The last is unusual in its fern-feeding habit and includes denizens of the forest habitats as well. Most of these genera extend into warm temperate areas, some, such as Athet is, strongly so. Many species migrate towards higher latitudes at times.

The Heliothinae are most diverse in semi-arid habitats from the tropics to Mediterranean latitudes. The hadenine genus Mythimna has taxa characteristic of both lowland open habitats and montane ones, and is diverse also at temperate latitudes. However, the graminaceous stem-borers in the Amphipyrinae appear to segregate into distinct tropical and temperate complexes, the latter perhaps allied to the Apamea group of genera that includes more general feeders (leaf, stem and root) on grasses. A few members of the tropical Sesamia Guenee complex extend into southern Europe.

The montane species are drawn mainly from genera diverse in temperate latitudes, particularly the eastern Himalayas, and extend through the mountains of the tropics often to south temperate latitudes. All noctuine genera are of this category, as is Phlogophora Treitschke of the Apamemi, though this genus may have its greatest richness within the tropics and subtropics. Most of the 'higher trifines' fall into this category though some, such as Apospasta Fletcher, Euplexidia Hampson and Xenotrachea Sugi, are virtually restricted to mountains in the tropics and subtropics.

Bornean endemism is highest at the specific level in the montane category, including one genus, Bornolis Gen. n., in the Hadeninae and several species found only in the higher zones of G. Kinabalu. Endemism is moderate in the lowland forest category, with many purely Sundanian species, and absent from the open habitat category where species widespread in the Indo-Australian tropics predominate, many extending also to Africa.


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