A Brief Spotlight on Scopariines

The moths of the Pyraloidea are perhaps one of the more under-appreciated sectors of lepidopteran diversity. With many thousands of species, they comprise a significant proportion of the order in terms of both taxonomic and ecological diversity. Nevertheless, with most species being small and dull in coloration, many Lepidoptera enthusiasts will tend to lump them in the too-hard basket for study. One subgroup of the pyraloids to which this issue definitely applies is the subfamily Scopariinae.

Scoparia spelaea, copyright Donald Hobern.

Close to 600 species of Scopariinae are known from around the world with the highest diversity found on tropical mountains and islands (Léger et al. 2019). They are mostly a mottled greyish in coloration, blending in among the rocks and tree trunks on which they settle during the day. Like other pyraloids, they have large palps that extend in front of the head; pyraloids as a whole are sometimes referred to as 'snout moths' in reference to the appearance this gives them. Forewing venation is characterised by clear separation of vein R₂ from R₃₊₄ and absence of CuP (Nielsen & Common 1991).

Meadow grey Scoparia pyralella, copyright Hectonichus.

The majority of scopariine species feed as larvae on mosses, living concealed within a slight silk web. A smaller number feed on dicotyledons or lichens. One New Zealand species, the sod webworm Eudonia sabulosella, has been known to cause economic damage to pasture during sporadic outbreaks. Other species generally do not cause significant impact to humans.

Eudonia lacustrata, copyright Tony Morris.

Identification of scopariines is notoriously difficult with many species closely approximating each other in pattern or exhibiting confounding intra-specific variation. The two largest genera Scoparia and Eudonia can only be reliably separated by examination of the genitalia. Two genera, the Indo-Australian Micraglossa and the Neotropical Gibeauxia, are distinguished by the presence of shiny golden scales on head, thorax and abdomen. With such significant challenges to their study, it would not be surprising if 600 species should turn out to be a marked under-estimate of their true diversity.

REFERENCES

Léger, T., B. Landry & M. Nuss. 2019. Phylogeny, character evolution and tribal classification in Crambinae and Scopariinae (Lepidoptera, Crambidae). Systematic Entomology 44: 757–776.

Nielsen, E. S., & I. F. B. Common. 1991. Lepidoptera (moths and butterflies). In: CSIRO. The Insects of Australia: A textbook for students and research workers 2^nd ed. vol. 2 pp. 817–915. Melbourne University Press: Carlton (Victoria).

Ophiusini Corrections

Earlier this year, I presented a post on the noctuoid moth tribe Ophiusini. As it turns out, that post includes some notable errors. One of the main sources I used, Zahiri et al. (2012), stated that Ophiusini "have a strongly modified apex to the proboscis, with strong and enlarged spines and erectile, reversed hooks that are used in fruit-piercing or lachrymal-feeding behaviour". As reviewed by Zilli (2021), such hooks on the proboscis are unique to a separate subgroup of the family Erebidae, the Calpinae. Ophiusini have thin, nail-like spines on the proboscis but no erectile hooks. They are still fruit-piercers but no ophiusins have been observed to date engaging in lachrymal feeding.

Artena dotata, copyright Shipher Wu.

Zilli (2021) had further comments on the historically fraught concept of Ophiusini. As noted in my earlier post, 'Ophiusini' has historically been recognised as a cosmopolitan group of moths but molecular studies have lead to its restriction to the Old World, North American exemplars being transferred to the related tribe Poaphilini. However, though the two groups are each supported as monophyletic by molecular data, they are not well defined morphologically. Characters previously thought distinct to one or the other do not always hold true. Ophiusini have been described as having reduced coremata but some ophiusins have coremata larger than those of some poaphilins. Ophiusins have been supposed to lack the waxy bloom on the pupa found in other noctuoids but some species do indeed have such a bloom. Some have pointed to the use of Euphorbiaceae as host plants by Poaphilini but not Ophiusini, but not all poaphilins feed on Euphorbiaceae and their use of this plant family is generally correlated with species being more generalist feeders overall.

One character that may yet distinguish the two tribes is the location of the androteca, a groove along the top of one of the leg segments in the male that contains a long brush of dense hairs (I'm not sure just what the function of this structure is meant to be but I would suspect something to do with dispersing pheromones). In Ophiusini, this structure is found on the femur of the fore leg. In Poaphilini, it is on the tibia of the mid leg. Nevertheless, Zilli (2021) questions the reliability of this feature: both arrangments are found in other tribes and neither alone is diagnostic.

Conversely, molecular phylogenies support the two tribes as sister taxa, and they share a number of distinctive features of the terminalia. While he does not formalise the suggestion, Zilli (2021) seems to feel that we might be better served by a return to a broader Ophiusini uniting the two tribes as one. I commented in my previous post that noctuoid classification has been in a continuous flux for as long as it has been a thing. It would be presumptuous to believe that it has finally been settled.

REFERENCES

Zahiri, R., J. D. Holloway, I. J. Kitching, J. D. Lafontaine, M. Mutanen & N. Wahlberg. 2012. Molecular phylogenetics of Erebidae (Lepidoptera, Noctuoidea). Systematic Entomology 37: 102–124.

Zilli, A. 2021. Tabwecala robinsoni gen. nov., sp. nov., from Vanuatu and its systematic postion in the 'Ophiusini-Poaphilini' clade (Lepidoptera, Erebidae). Nota Lepidopterologica 44: 193–211.

Piercing Fruit and Piercing Souls

The moths of the superfamily Noctuoidea are one of the most diverse subsections of the Lepidoptera, with probably somewhere between fifty and seventy thousand species known to date (Zahiri et al. 2012; as with other massively diverse clades, the lack of proper checklists and revisions makes the question of species number surprisingly difficult to answer). For many people, the classic image of a 'moth' will evoke a noctuoid: broad-winged, often nocturnal, often predominantly brown or grey in colour. Obviously, a group this size is going to have a complex taxonomy, and one of the significant subgroups of the noctuoids is the tribe Ophiusini.

Variable drab moth Ophiusa mejanesi, copyright Bernard Dupont.

Historically, the classification of noctuoids has been something of a mess. One researcher commented in 1975 that "It is exceptional to find any two authors who use the same combination of subfamily names within the Noctuidae" and Zahiri et al. admitted in 2012 that the validity of this statement still stood. Until recently, the majority of noctuoids were dumped in a broad family Noctuidae but recent studies (particularly influenced by molecular data) have lead to a significant rearrangement. As a result, the Ophiusini went from being usually placed in the family Noctuidae, subfamily Catocalinae, to the family Erebidae, subfamily Erebinae. A number of genera previously included in the Ophiusini were also transferred elsewhere; most notably, these included all New World representatives so the Ophiusini are now regarded as an exclusively Old World group.

Thyas juno, copyright Alexey Yakovlev.

The Ophiusini are mostly robust-bodied moths with wings of a fairly uniform background colour marked with simple, linear lines on the forewings. The males lack well-developed coremata (eversible structures used for dispersing pheromones) on the genital valves. The caterpillars are elongate semi-loopers with the front two pairs of abdominal prolegs much reduced compared to the rear two pairs. Larvae have been recorded from a wide range of host plant families but the most commonly exploited hosts are members of the Combretaceae and Myrtaceae (Holloway 2005). The pupa lacks the waxy bloom found in many other erebines.

Caterpillar of guava moth Ophiusa disjungens, copyright Robert Whyte.

Many members of the Ophiusini also have a modified apex to the adult proboscis bearing strong, enlarged spines and reversed, erectile hooks (Zahiri et al. 2012). This formidable apparatus is used to pierce the skins of fruits, allowing the moth to feed on their juice. As well as damage caused by browsing caterpillars, ophiusins may therefore also be of concern to horticulture due to damage from this fruit-piercing behaviour. As well as the damage caused by the moth itself, the resulting holes may allow the fruit to be attacked by disease or other insects not capable of breaching the rind themselves. The modified proboscis may also function in what is somewhat daintily referred to as lachrymal feeding: the process of applying the proboscis to the eyes of mammals (more rarely birds) and feeding on secreted fluids. Yes, these are moths that can potentially destroy an orchardist's crop... and then proceed to drink his tears.

REFERENCES

Holloway, J. D. 2005. The moths of Borneo (part 15 & 16): family Noctuidae, subfamily Catocalinae. Malayan Nature Journal 58: 1–529.

Zahiri, R., J. D. Holloway, I. J. Kitching, J. D. Lafontaine, M. Mutanen & N. Wahlberg. 2012. Molecular phylogenetics of Erebidae (Lepidoptera, Noctuoidea). Systematic Entomology 37: 102–124.

Blue Moon

Male blue moon butterfly Hypolimnas bolina, photographed by Comacontrol.

My native country of New Zealand is not home to a large diversity of butterflies. Only a couple of dozen or so species are known from the entire country. It would not be unreasonable for a keen butterfly spotter to attempt to track down them all. But one particular species of butterfly generally included in New Zealand lists would a touch of luck: the aptly named blue moon Hypolimnas bolina.

This is because the blue moon is not a regular resident of New Zealand (I've personally never spotted one). It is native to a wide region stretching from Madagascar and India to Japan and northern Australasia where it is usually referred to by the more prosaic name of common or greater eggfly. The only examples found in New Zealand are vagrants who lost their way on southwards migrations. Nevertheless, such vagrants are regular enough for its local appellation to be thought worth coining. Not only does it reflect their rarity, it also describes the appearance of the male, with the wings bearing blue-ringed white spots on a black background.

Two females of Hypolimnas bolina. On the left, a mimetic individual, copyright Greg Hume; on the right, a non-mimetic individual, copyright W. A. Djatmiko.

The appearance of the female is a bit harder to explain because it can vary between individuals. Females of the eggfly genus Hypolimnas are commonly mimics of other, poisonous butterflies of the subfamily Danainae, to which eggflies are only distantly related (both groups belong to the family Nymphalidae but eggflies are placed in the subfamily Nymphalinae). For instance, the diadem or danaid eggfly H. misippus of Africa and Asia (and also introduced into parts of the Americas adjoining the Caribbean) is a mimic of the plain tiger Danaus chrysippus. The chosen model of H. bolina in the western part of its range is the common crow Euploea core and in the region of India almost all females are a remarkably good copy of that species (above left). But as one moves east, one starts seeing females of H. bolina that are not mimics like the individual shown above right; by the time one reaches Australia these make up the greater part of the population. Mimetic females may also vary to resemble different Euploea species, depending on which model is locally present.

Female danaid eggfly Hypolimnas misippus, copyright Raju Kasambe. Males of this species are similar to those of H. bolina but lack the blue rings around the white spots on the wings.
There are about two dozen species of Hypolimnas eggflies found in various parts of the Old World tropics. Hypolimnas misippus is also found in parts of the Americas around the Caribbean where its presence is usually explained as the result of an early introduction (possibly, and somewhat poignantly, in connection to the slave trade). Their vernacular name is probably derived from the unique behaviour (for butterflies) of a number of species whose females stand guard over their eggs, beating their wings over them to protect them from predators until hatching. About two-thirds of Hypolimnas species are mimics. In some of these species, both sexes are mimetic; others resemble H. bolina and H. misippus in that only the females are mimics (Vane-Wright et al. 1977). One might be tempted to ask why this variation exists. One point to be considered is that there are limits on when mimicry is likely to be effective. The mimic needs to be much less abundant than its model, otherwise potential predators may not learn to associate the distinctive coloration with the toxic original. Swinhoe (1896) noted that males of Hypolimnas misippus were very active, aggressively defending their territories from other butterflies, and suggested that this agility might provide males with alternative defences to mimicry. The more sedentary females (especially when egg-guarding) might be expected to benefit more from the passive protection mimicry provides, but mimesis might be expected to disappear in areas where their model is less abundant.

REFERENCES

Swinhoe, C. 1896. On mimicry in butterflies of the genus Hypolimnas. Journal of the Linnean Society, Zoology 25: 339–348.

Vane-Wright, R. I., P. R. Ackery & R. L. Smiles. 1977. The polymorphism, mimicry, and host plant relationships of Hypolimnas butterflies. Zoological Journal of the Linnean Society 9: 285–297.

Large Yellow Underwings

Above is an example (copyright Richard) of the large yellow underwing Noctua pronuba, the most widespread species of its genus. Noctua pronuba is a relatively large moth, with a wingspan of up to 60 mm. The forewings are fairly dull and dark in colour, but the hindwings are a bright yellow-orange (hence the vernacular name) with a black border. It can usually be found out and about in mid summer to early autumn. Its larvae are one of the types of caterpillar known as 'cutworms', which live buried in the soil during the day and emerge at night to feed. They get their vernacular name because their soil-dwelling habits mean that they tend to feed on plants from the base, often toppling small plants and seedlings like a lumberjack taking down a tree. The larvae of the large yellow underwing are not overly discerning in their food preferences; though they most often feed on grasses, they will quite happily dine on other herbaceous flowering plants such as legumes.

Larva of Noctua pronuba, copyright Nigel Richards.

The large yellow underwing is native to a wide part of the Palaearctic region, i.e. Europe and northern Asia. In 1979, it was also found introudced to Nova Scotia in North America. Since then, it has spread rapidly and can now be found over much of temperate North America, reaching British Columbia in the west and Louisiana in the south (Copley & Cannings 2005). The large yellow underwing is a strong flier and is known to undertake significant migrations in its native range. Females may also lay large numbers of eggs at a single time on the underside of leaves or on non-host plant substrates, where they can easily be carried between locales by human transportation. For the most part, a significant impact of the large yellow underwing on native or horticultural production in North America has not been recognised, though a number of authors have suggested that this species' generalist diet may lead to any such impact going unnoticed.

The Azorean Noctua atlantica, copyright Jens Jacobasch.

Historically, a large number of species have been included at one time or another in the genus Noctua, but a revision of this and closely related genera by Beck et al. (1993) cut it down on the basis of larval and male genital morphology to just two species. The only other species retained in Noctua sensu stricto by Beck et al. was N. atlantica, a species endemic to the Azores islands west of Portugal. Noctua atlantica is somewhat smaller than N. pronuba with duller hindwing coloration. It is restricted in its home range to the laurisilva, a particular subtropical forest type dominated by laurels and other evergreen, broad-leaved trees. Noctua pronuba is also found on the archipelago but inhabits are wider range of habitats. Genetic comparisons between the two species suggest that their populations diverged about five million years ago, a time frame that is not inconsistent with the origin of the Azores archipelago about four million years ago (Montiel et al. 2008). Perhaps an early population of N. pronuba became isolated on the Azores long enough to evolve into a distinct species, followed by a later re-colonisation of N. pronuba from the mainland. This would be similar to patterns seen in my home country of New Zealand, where repeated immigrations from Australia have lead to species pairs such as the endemic takahe Porphyrio hochstetteri and the more widespread pukeko P. melanotus, or the endemic (now extinct) Eyles' harrier Circus eylesi and the modern swamp harrier C. approximans.

REFERENCES

Beck, H., L. Kobes & M. Aloha. 1993. Die generische Aufgliederung von Noctua Linnaeus, 1758 (Lepldoptera, Noctuidae, Noctuinae). Atalanta 24 (1–2): 207–264.

Copley, C. R., & R. A. Cannings. 2005. Notes on the status of the Eurasian moths Noctua pronuba and Noctua comes (Lepidoptera: Noctuidae) on Vancouver Island, British Columbia. J. Entomol. Soc. Brit. Columbia 102: 83–84.

Montiel, R., V. Vieira, T. Martins, N. Simões & M. L. Oliveira 2008. The speciation of Noctua atlantica (Lepidoptera, Noctuidae) occurred in the Azores as supported by a molecular clock based on mitochondrial COI sequences. Arquipélago 25: 43–48.