Ghost Moths and Other Obscurities

During my early years in rural New Zealand, I would often take note of the variety of insect life that could be seen coming to the screen doors at night, attracted by the light from inside the house. Among the most spectacular animals that would sometimes turn up was a gigantic pale green moth, about three inches long as it crawled across the screen. This was the puriri moth Aenetus virescens, perhaps New Zealand's best known member of the moth clade Exoporia.

Puriri moth Aenetus virescens, copyright Nga Manu Images NZ.

The Exoporia is one of the more basal moth groups alive today. The name of the clade refers to one of its most distinctive features: a female genital system with separate external openings for the seminal receptacle and the oviduct, meaning that the male's sperm has to travel along an external groove between the two if it is to fertilise the egg (in other Lepidoptera, there is a single cloacal opening, or there are separate openings but the cavities are connected by an internal duct). Other important features of the clade include dicondylic antennae, with two instead of just one articulations between the antenna and the head, and a male reproductive system without a sclerotised tubular intromittent organ (Kristensen 1978; the males instead have the gonopore opening on a shorter protuberance). Six families are generally recognised within the clade but the majority of species (including the puriri moth) belong to just one of these families, the Hepialidae, commonly known as the ghost moths.

Bentwing ghost moth Zelotypia stacyi, copyright CSIRO.

Hepialids definitely buck the phylogenetic trend among moths. Lepidopterists commonly divide the moth and butterfly order between two main groupings, somewhat self-explanatorily referred to as Micro- and Macrolepidoptera. To some extent, this is merely a division of convenience (the practicalities of working with smaller and larger moths can be quite different) but Macrolepidoptera is also used as the name of a major clade within the order with micro-Lepidoptera then indicated for any lepidopteran not belonging to this clade. By this measure, hepialids are by far the largest micro-Lepidoptera out there (most other examples are unquestionably micro). I've already alluded to the fifteen centimetre wingspan of the puriri moth but this isn't even close to being the largest hepialid out there. The honour perhaps goes to the bentwing ghost moth Zelotypia stacyi of eastern Australia which reaches a wingspan of 25 centimetres, a full ten inches. The larvae of hepialids are commonly borers in live trees; the puriri moth, for instance, gets its name because it burrows into puriri trees Vitex lucens. Other species live as larvae in burrows in soil, emerging at night to feed on pasture or leaf litter, or feeding externally on tree roots. Adult hepialids are short-lived and do not feed, and as such their proboscis is reduced or absent. They may emerge en masse at particular times of year. Following mating, females may scatter their eggs at random during flight or lay them in loose masses on the ground, with larvae finding a suitable food source after hatching. Because of the high mortality rates associated with this scatter-shot method, laying rates can be exceedingly large: females of some genera may produce around 18,000 eggs apiece (Nielsen & Common 1991).

Mnesarchaea acuta, copyright George Gibbs.

The other exoporian families are all much less diverse and more localised. They are also all small moths, far more typical 'micro-Lepidoptera'. The genus Mnesarchaea, endemic to New Zealand, retains functional mouthparts and is believed to be the sister group to all other exoporians. Larvae of Mnesarchaea live in silken galleries among mosses and liverworts, feeding on moss and liverwort leaves, algae, fungal spores and the like. The remaining families all lack functioning mouthparts as adults but their habits are otherwise all but unknown. Anomoses hylecoetes is placed in its own family known from rainforests in eastern Australia. The family Neotheoridae was until recently known from only a single female specimen collected in Brazil, but a few further species of this family were described recently by Simonsen & Kristensen (2017). Prototheora, another genus held worthy of its own family, is found in southern Africa. Finally, the family Palaeosetidae is known from a small number of genera with disjunct distributions in Colombia, south-east Asia and Australia. Because of its scattered distribution, some authors have questioned whether this last family is monophyletic, but an analysis of exoporian phylogeny by Simonsen & Kristensen (2017) continued to support it as such. It is not impossible that this family is more widespread, its apparent rarity due to the overlooking of small moths emerging for only very short periods, living just long enough to breed and deposit their eggs in as-yet-unknown locales.

REFERENCES

Kristensen, N. P. 1978. A new familia of Hepialoidea from South America, with remarks on the phylogeny of the subordo Exoporia (Lepidoptera). Entomologica Germanica 4 (3–4): 272–294.

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).

Simonsen, T. J., & N. P. Kristensen. 2017. Revision of the endemic Brazilian 'neotheorid' hepialids, with morphological evidence for the phylogenetic relationships of the basal lineages of Hepialidae (Lepidoptera: Hepialoidea). Arthropod Systematics and Phylogeny 75 (2): 281–301.

ID for Heather?

The deadine for my crowdfunding drive has been extended. Thanks to your support, I am over 40% of the way towards success! But I'm still going to need everyone's help if I'm to be succesful. Please visit my page at Experiment.com and consider offering your support!

I was recently contacted by Heather Adamson who wanted to know if I could identify the animal in the above picture. She photographed it on an old post in the region of West Coolup, south of Mandurah here in Western Australia. I can tell her that it is some form of Lepidoptera larva (in other words, a caterpillar) and it looks like it may be beginning to weave itself a cocoon. Beyond that, I couldn't say. Do any of my readers have a better idea of what it is than I do?

Update: I shared this post to the Western Australian Insects group on Facebook, and Daniel Heald has suggested that Heather's photo may show the pupa of a lymantriid moth Teia athlophora. This species constructs itself a loose, cage-like cocoon from its own irritant hairs. The male, when he emerges, is a fairly standard looking brown moth, but the female is fat and flightless with only tiny stubs of wings. She will continue to live in and around her pupal cocoon, awaiting visits from courting males.

Yponomeutoids and their Boring Larvae

...because some puns will never die.

Larvae of the bird-cherry ermine moth Yponomeuta evonymella, from here.

As noted in an earlier post, most people's perception of Lepidoptera, 'butterflies and moths', is heavily skewed towards the larger members of the group while the greater diversity is actually to be found among the smaller species (this sentence, offhand, could be repurposed for just about any animal group). The subject of today's post, the Yponomeutoidea, are a clade of about 1800 species of the much-overlooked smaller Lepidoptera. Yponomeutoids have been recognised as a group primarily on the basis of a single synapomorphy, the presence of posterior lobes on the eighth abdominal pleura (a 'pleuron' being a sclerite on the side of the body wall). This character has been secondarily lost in some subgroups of the Yponomeutoidea, but the clade is also supported by molecular data (Sohn et al. 2013). The larvae of yponomeutoids are plant-feeders, with the clade including some species that feed internally as leaf-miners or stem-borers, and others that feed externally on leaves though they do conceal themselves within a silk webbing. A number of species are effectively both, starting out as internal leaf borers then changing to external leaf webbers as they grow larger. Some species are notable horticultural pests, such as the diamondback moth Plutella xylostella that attacks brassicas*.

*Horticulture is the only human endeavour in which you will hear something described as 'attacking' a cabbage.

Apple leaf miner Lyonetia clerkella, photographed by Jeff Higgott.

The most recent review of the clade's systematics by Sohn et al. (2013) recognised eleven families within the Yponomeutoidea, but this was not the first re-organisation of the yponomeutoids and it will probably not be the last. Many of the families have few distinct synapomorphies, and a few recognised by Sohn et al. lack recognised morphological synapomorphies altogether and are united by molecular analysis only. Most yponomeutoids follow the usual microlepidopteran pattern of being small and generally brown, but there are some exceptions. The 'mega-plutellids' of New Zealand and Tasmania (placed by Sohn et al. in the family Glyphipterygidae rather than Plutellidae) are relatively large, with the Tasmanian Proditrix nielseni having a wingspan of over six centimetres (McQuillan 2003). The adult of the ailanthus webworm Atteva pustulella has a fairly striking array of black-ringed white patches on an orange background.

Galapagos bitterbush moth Atteva hysginiella, photographed by Rich Hoyer.

Though the clade is diverse in its habits overall, feeding habits tend to be conserved within each of the constituent families. It is not entirely clear whether internal or external feeding represents the original lifestyle of the yponomeutoids, though there may be a slight tip towards internal feeding. If this is the case, then external feeding has arisen within the yponomeutoids on a number of occasions, and the pine needle miners of the genus Zelleria in the family Yponomeutoidea probably represent at least one case of a internal feeder derived from externally feeding ancestors. Some families show a bias towards particular plant hosts: the Attevidae are primarily found on Simaroubaceae, while the Bedeliidae show a preference for Convolvulaceae. Others are more diverse in their selection.

REFERENCES

McQuillan, P. B. 2003. The giant Tasmanian ‘pandani’ moth Proditrix nielseni, sp. nov. (Lepidoptera: Yponomeutoidea: Plutellidae s. l.) Invertebrate Systematics 17: 59-66.

Sohn, J.-C., J. C. Regier, C. Mitter, D. Davis, J.-F. Landry, A. Zwick & M. P. Cummings. 2013. A molecular phylogeny for Yponomeutoidea (Insecta, Lepidoptera, Ditrysia) and its implications for classification, biogeography and the evolution of host plant use. PLoS One 8(1): e55066. doi:10.1371/journal.pone.0055066.

Deceptive and Poisonous Sisters

Iphicleola sister Adelpha iphicleola, photographed by Arthur Chapman.

The butterfly genus Adelpha includes 85 species, many with multiple subspecies, found widely in North and South America (Willmott 2003a). Some of you may recognise 'adelpha' as the Greek word for 'sister', which is also the vernacular name for these butterflies. Supposedly, the white stripes on the wings of many species resemble the edges of a nun's habit (or, at least, so sayeth Wikipedia). The sisters belong to a group of butterflies called the Limenitidini, members of which tend to sit with their wings open when resting, and have a distinctive gliding flight pattern in which the wing tips are pointed downwards (Willmott 2003b). Adelpha is the only genus of Limenitidini found in South America. In North America, Adelpha bredowii is found as far north as Oregon, while in South America species are found down to Uruguay. Not surprisingly, the highest diversity is found in the tropics, though some species are relatively uncommon throughout their ranges (Willmott 2003a).

As caterpillars, Adelpha species feed on a wide variety of food plants, with individual species varying from very host-specific species to broadly catholic species. As befits Neotropical caterpillars, some species possess a ludicrous array of protrusions and outgrowths:

Caterpillar of Adelpha serpa selerio, photographed by Artour A.
When feeding on a leaf, the caterpillars leave the midrib intact, and use it as a support when resting. Over time, they extend the midrib using a combination of faecal pellets and silk to extend their support, and they also sit on this support when moulting. After moulting to the final larval instar, they leave the support and rest on the upper leaf surface. They also attach masses of mixed silk and faecal pellets to the base of their support or hanging off it. One species, Adelpha basiloides, builds small, curved, larva-shaped faecal masses that it places on the leaf surface several millimetres away from its support: Aiello (1984) speculated that these might functions as decoys to distract potential predators from the real caterpillar.

Arizona sister Adelpha eulalia, photographed by Tom Bentley.

The adults of Adelpha have a reputation for being tricky to identify; DeVries described them as "the most difficult and trying taxonomically of all the nymphalids". For a long time, Adelpha species were divided into groups on the basis of their wing patterning, but comparisons with other features such as caterpillar morphology have revealed that species with similar wing patterns are often not closely related (Aiello 1984; Willmott 2003b). Instead, it has been suggested that mimicry has been a significant factor in the genus' evolution: certain species feeding as caterpillars on toxic plants such as members of the Rubiaceae (and hence sequestering the plant toxins to render themselves distasteful) are imitated by species with more innocuous diets. Because the appropriate model for such mimicry may vary with distribution, some mimetic species are quite variable in appearance; prior to the genus' revision by Willmott (2003a), some members of a single species were classified in entirely separate species groups!

REFERENCES

Aiello, A. 1984. Adelpha (Nymphalidae): deception on the wing. Psyche 91 :1-46.

Willmott, K. R. 2003a. The Genus Adelpha: Its systematics, biology and biogeography (Lepidoptera: Nymphalidae: Limenitidini). Scientific Publishers.

Wilmott, K. R. 2003b. Cladistic analysis of the Neotropical butterfly genus Adelpha (Lepidoptera: Nymphalidae), with comments on the subtribal classification of Limenitidini. Systematic Entomology 28: 279-322.

Colour vs Crypsis

The southeast Asian Lyssa zampa, a large nocturnal uraniine. Photograph by Alexey Yakovlev.

Even if you don't know much about insects, you've probably been taught the difference between a butterfly and a moth. Butterflies are ornate, colourful and active during the day, while moths are... ornate, colourful and active during the day?

A cryptic epiplemine Crypsicoela subocellata, photographed by Stephen Luk.

The Uraniidae are a family of about 700 species of mostly pantropical moth. The family is united primarily by their distinctive sexually dimorphic tympanal organs: in females, the tympanal organs open ventrally on the first abdominal sternite (as in a number of other moths), but in males they open dorsally or laterally at the junction of the second and third segments (Scoble 1995). About 600 of the 700 species of uraniid are assigned to the subfamily Epipleminae, and are generally nocturnal, brown and cryptic. Many epiplemines roll their wings up when at rest, so that they resemble a small brown stick.

The South American migratory Urania fulgens. Photo from here.

However, some members of the subfamily Uraniinae have become diurnal. These diurnal species have brightly iridescent wings with prominent tails, and have often been compared to swallowtail butterflies. One of the best-known species is Urania fulgens, a South American species that migrates north into Central America at certain times of year. Migrating individuals may reach as far north as the southern United States.

REFERENCES

Scoble, M. J. 1995. The Lepidoptera: Form, function and diversity. Oxford University Press.

Blues (Not All of Them Blue) (Taxon of the Week: Polyommatus)

I'm heading into the field tomorrow for two weeks and won't be able to respond to comments on this post, so I'll just give you a light coverage for the latest Taxon of the Week, the butterfly genus Polyommatus:


Male of the blue butterfly Polyommatus escheri, a widespread species in Europe. Photo by Eric Sylvestre.

Polyommatus is a genus of about 200 species of butterfly found in Eurasia and northernmost Africa with the highest diversity seemingly around west central Asia from Turkey to Iran. It is divided into a number of subgenera (recognised as separate genera by some authors) with the largest, Agrodiaetus, including about 130 species (Wiemers et al. 2010). As the common name 'blue' would suggest, the males of most species are a brighter or paler shade of blue; females are generally brown.


Female of Polyommatus semiargus (or Cyaniris semiargus). Photo by James Lindsey.

The majority of Polyommatus species lay their eggs on plants of the family Leguminosae. Like many other species of the family Lycaenidae to which they belong, caterpillars of Polyommatus show an association with ants. In the species in which this association has been most studied, the common blue P. icarus, the association is facultative only; the caterpillars may reach maturity without ever being tended by ants (other lycaenid species may require tending to survive).


Female of Polyommatus agestis. Photo by Hans-Peter.

When the caterpillar of Polyommatus icarus reaches its fourth instar, it starts producing honeydew from an organ on its abdomen. It will also produce vibrations that travel through the ground and may attract ants. Arriving ants are presented by the caterpillar with honeydew, in return for which they tend the caterpillar and protect it from predators and parasitoids. The caterpillar also possesses a pair of eversible tentacles on either side of the honeydew organ that it displays when it registers the presence of ants; displaying the tentacles seems to encourage attention from the ants somehow, perhaps by releasing pheromones (Axén et al. 1996). When the caterpillar moults into a chrysalis, the ants bury it under a light covering of soil and leaf litter where it remains until the adult butterfly emerges after two weeks.


Polyommatus ainsae (or Agrodiaetus ainsae), an inhabitant of northern Spain. Photo by Teresa Farino.

REFERENCES

Axén, A. H., O. Leimar & V. Hoffman. 1996. Signalling in a mutualistic interaction. Animal Behaviour 52: 321-333.

Wiemers, M., B. V. Stradomsky & D. I. Vodalazhsky. 2010. A molecular phylogeny of Polyommatus s. str. and Plebicula based on mitochondrial COI and nuclear ITS2 sequences (Lepidoptera: Lycaenidae). European Journal of Entomology 107: 325-336.

Caterpillars and their Capers (Taxon of the Week: Belenois)

The brown-veined white, Belenois aurota, of southern Africa. Photo from Bronberg Conservancy.

Belenois is a genus of about thirty species of butterfly of the family Pieridae found in tropical and subtropical regions of the Old World, with the greatest concentration of species in Africa. The caterpillars feed on plants of the caper family Capparaceae, though Moulds (1999) suggested that early records of 'cabbage whites' feeding on Brassica species in Australia prior to the confirmed introduction of any Pieris species might refer to Belenois java (the families Capparaceae and Brassicaceae are very closely related). Like most other pierids, Belenois species are medium-sized butterflies (the sole Australian species, B. java, has a wingspan of 55 mm - Braby 2000) with white or yellow background coloration patterned with black or brown on the wings. Individuals of a single species may vary in coloration patterns. Studies on B. java teutonia, which has distinct dark and pale forms, found that larval food species was one factor potentially affecting variation - caterpillars raised on Capparis umbonata always emerged from their pupae as dark form individuals, caterpillars from C. lasiantha were always pale, while caterpillars from C. spinosa could be either dark or pale (Braby, 2000).


The African veined white, Belenois glidica abyssinica. Photo by Johan van Rensburg.

Migratory habits have been recorded for a number of Belenois species, particularly B. java in Australia and B. aurota in southern Africa. Belenois aurota is one of the most abundant butterfly species within its range - one observer recorded witnessing a migration of about 500,000 individuals in Lesotho (Kopij 2006). A number of females will lay their eggs together in loose clusters on a suitable host plant. Braby (2000) notes that in some seasons a single tree may carry tens of thousands of eggs of B. java and the tree may end up being completely defoliated by the voracious caterpillars. Mortality among the caterpillars is high; only a few will reach adulthood.


The caper white, Belenois java teutonia, of Indonesia, New Guinea and Australia. Other subspecies of this species are found on islands of the Pacific. Photo by Peter Shanks.

REFERENCES

Braby, M. F. 2000. Butterflies of Australia: their identification, biology and distribution vol. 1. CSIRO Publishing: Collingwood (Australia).

Kopij, J. 2006. Lepidoptera fauna of Lesotho. Acta Zoologica Cracoviensia 49B (1-2): 137-180.

Moulds, M. S. 1999. The history of Australian butterfly research and collecting. In Biology of Australian Butterflies (R. L. Kitching et al., eds) pp. 1-24. CSIRO Publishing: Collingwood (Australia).

The Butterflies Get All the Glory (Taxon of the Week: Gelechioidea)

Caterpillar of a parsnip moth, Depressaria daucella (Depressariidae or Oecophoridae). Depressaria moths are notable for feeding on toxic umbelliferous host plants that other animals (for instance, certain Greek philosophers) find distinctly unpalatable. Photo by Percherón.

The Lepidoptera, butterflies and moths*, are one of the most familiar groups of insects, and have the enviable advantage of tending to receive a more favourable response from the general public than other insects do. Some Lepidoptera, particularly the butterflies, are almost treated as honorary vertebrates - they receive a degree of attention and enthusiasm usually reserved for those animals of a more endoskeletal disposition. You might be forgiven, then, for assuming that the Lepidoptera are overall a well-known and studied order - but you'd still be wrong.

*Though in our lab, they tend to get referred to simply as "leps".

Traditionally, Lepidoptera have been divided into two, reasonably self-explanatory, groups - the microlepidoptera and macrolepidoptera. Though originally divided simply by size, the terms have been redefined in recent years on a phylogenetic basis - the name Macrolepidoptera has been attached to a particular clade, while leps outside this clade are dubbed microlepidoptera. The intuitive meanings of the names still work reasonably well - the majority of large Lepidoptera are indeed Macrolepidoptera (though the often very sizeable Hepialidae are, phylogenetically speaking, microlepidoptera). And, not surprisingly, it is the Macrolepidoptera that get most of the attention, while the microleps (which, just to make the point, probably constitute the greater part of lepidopteran diversity) tend to get shoved to one side.


Esperia sulphurella, Oecophoridae. Larvae of this species feed on rotting wood. Photo by Keith Edkins.

The Gelechioidea are a large microlepidopteran superfamily. They are spectacularly diverse - Hodges (1998) referred to there being well over 16,000 described species. As if this wasn't impressive enough, perhaps only about a quarter of the world's gelechioids have been described. Most of the Gelechioidea are extremely small - one of the largest, Cryptophasa setiotricha, is 25 mm long, while one of the smallest is Siskiwitia falcata, a mere two millimetres in length (Hodges, 1998). Like many other tiny moths, the wings often have a long fringe of hairs. The larvae of gelechioids are usually retiring herbivores, often concealing themselves in a web of silk or binding leaves to form a hide. Some are detritivores or fungivores, while a few have become carnivores of other insects such as scales (Kaila, 2004). The monophyly of the Gelechioidea is not certain - the morphological analysis of Kaila (2004) supported gelechioid monophyly, but three of the four supporting characters were homoplasious with other Lepidoptera, while the only character unique to Gelechioidea (antennae meeting mesally in the pupa) had been lost in a number of gelechioid subgroups.


Oecophora bractella (Oecophoridae), an atypically colourful gelechioid (yes, I know that means that all the photos are of oecophorids, but you see, most gelechioids can basically be described as "kind of brown"). Photo by Sean McCann.

Homoplasy was similarly rife within the superfamily itself. Kaila (2004) resolved two major clades, a "gelechiid lineage" including (among others) the Gelechiidae, Cosmopterigidae and Coleophoridae, and an "oecophorid lineage" with the Xyloryctidae, Oecophoridae and Elachistidae, but both were supported solely by homoplasious characters. Bucheli & Wenzel (2005) used molecular data as well as morphology, but included less taxa in their analysis than Kaila (2004) - they continued to support the oecophorid lineage, but resolved the gelechiid lineage as paraphyletic. Probably as a result of such rampant homoplasy, no two revisions have agreed on the best way to divide the gelechioids into families - the major families listed are fairly safe, but various minor "family-type groups" move in and out of them at will.

Relatively few gelechioids are of economic significance to humans. A few are plant pests (such as Pectinophora gossypiella, the cotton bollworm) or can feed on stored grain or textiles, but for the most part they are just as retiring as they look. There's still an awful lot of them, though.

REFERENCES

Bucheli, S. R., & J. Wenzel. 2005. Gelechioidea (Insecta: Lepidoptera) systematics: A reexamination using combined morphology and mitochondrial DNA data. Molecular Phylogenetics and Evolution 35 (2): 380-394.

Hodges, R.W., 1998. The Gelechioidea. In Lepidoptera: Moths and Butterflies (N. P. Kristensen, ed.) pp. 131–158. Walter de Gruyter, Berlin and New York.

Kaila, L. 2004. Phylogeny of the superfamily Gelechioidea (Lepidoptera: Ditrysia): an exemplar approach. Cladistics 20 (4): 303-340.

The Sphinxes that aren't like the Others (Taxon of the Week: Smerinthini)

Female of the smerinthin moth Marumba quercus. Photo by Tony Pittaway.

Quick question - should the plural of "sphinx" be "sphinxes" or "sphinges"?

The sphinx moths or hawkmoths (Sphingidae) are one of the easiest lepidopteran families to recognise. Sphinxes tend to be fairly large (but not inordinately so), and are generally the speedsters of the moth world. Their rapid mobility is reflected in their wings, which are narrower, more streamlined and more pointed than those of other moth families. Sphinxes are not usually brightly-coloured, but they are none the less very handsome animals, with dapper patterns of earthy colours such as browns and soft pinks. The name "sphinx" is derived from their caterpillars - sphinx caterpillars have a way of sitting with the front of the body raised that is supposed to be reminiscent of the famed Egyptian statue.

Adult sphinxes are most famed as nectar feeders - with their long proboscides and ability to hover in front of the flowers they feed on, Old World sphinx moths have been described as the ecological counterparts of New World hummingbirds (I won't repeat the Xanthopan praedicta story here, but look it up if you're interested). One group of sphinxes, however, has decided to buck the trend. Sphinxes are divided into three subfamilies - Sphinginae, Macroglossinae and Smerinthinae. Smerinthinae are distinguished from the other two subfamilies because they lack the super-long proboscides. In at least one of the smerinthine tribes, Smerinthini, the adults are completely non-feeding (the subfamily as a whole is sometimes described as such, but the presence of pollen on proboscides of Ambulycini indicates that members of that tribe are still flower feeders - Beck et al., 2006). Adult Smerinthini are weaker fliers than other sphinx moths, and have less streamlined wings to match. Also, while caterpillars of other subfamilies tend to be fussy eaters, Smerinthini are relative gourmands, feeding on a wide range of host plants.


Paonias astylis, one of the few North American Smerinthini. The small-eyed and blinded sphinxes of the genus Paonias (so-called, I'm guessing, because the unusual relative position of the fore- and hindwings means that the eyespots on the latter are hidden) are perhaps some of the most distinctive sphinx moths. Photo by Jim McCormac.

Sphingidae as a whole are regarded as good dispersers, and European sphingid species tend to have wider ranges than moths of other families. However, a study of sphingid distributions in Indonesia found that, in line with their lower dispersal capabilities, smerinthine species showed a higher turnover between islands than members of the other two subfamilies (Beck et al., 2006). Smerinthini are mostly found in the Old World - only two species are found east of "Lydekker's line" between the Moluccas and New Guinea, and a handful of species are found in Nearctic North America.

It is easy to imagine a connection between the distinctive smerinthine life cycle and their poor dispersive abilities - with their short-lived adults and polyphagous larvae, female Smerinthini have neither the freedom nor the need to invest a lot of time in seeking out suitable host plants for their eggs. What is more uncertain is whether the smerinthine life cycle is derived from a more typically sphingid ancestor. The Smerinthinae have been suggested to be the basalmost subfamily of Sphingidae, and in some features they are more like members of closely-related families than other sphingids - their short proboscides (like Brahmaeidae) and preference for tannin-bearing trees over tannin-free shrubs (like Saturniidae). On the other hand, a genetic analysis by Regier et al. (2001) found support for a Sphinginae-Smerinthini clade excluding Macroglossinae. Mind you, Regier et al.'s analysis did not include representatives from the other smerinthine tribes.

Oh yes, and at least some Smerinthini have stridulatory apparatuses on their genital valves (Conner, 1999). These are singing moths.

REFERENCES

Beck, J., I. J. Kitching & K. E. Linsenmair. 2006. Wallace's line revisited: has vicariance or dispersal shaped the distribution of Malesian hawkmoths (Lepidoptera: Sphingidae)? Biological Journal of the Linnean Society 89 (3): 455-468.

Conner, W. E. 1999. 'Un chant d'appel amoureux': acoustic communication in moths. Journal of Experimental Biology 202: 1711-1723.

Regier, J. C., C. Mitter, T. P. Friedlander & R. S. Peigler. 2001. Re: Phylogenetic relationships in Sphingidae (Insecta: Lepidoptera): initial evidence from two nuclear genes. Molecular Phylogenetics and Evolution 20 (2): 311-316.

And then... Beautiful butterfly!

Susannah at Wanderin' Weeta has managed to photograph a caterpillar in the process of chrysalising! (if that's a word) Wow.

Taxon of the Week: Butterflies on Parasites

This week I've got something a little more recognisable to go on, at least in general - butterflies! I've referred to butterflies in the past as "honorary vertebrates", as they seem to be about the only group of invertebrates that receive as much attention and recognition as vertebrate groups seem to. What those of us in the know can tell you, though, is that really butterflies are just a flashy kind of moth. Specifically, today I'll be looking at butterflies of the genus Delias.

Delias, commonly known for no particular reason as 'jezebels', are found from southern and south-east Asia to the northern tip of Australia (the image above is of Delias aglaia and is from Answers.com). The bright colouration in the photo above is usually restricted to the underside of the wings, while the upper side is far plainer - most often white with black edging, as shown in the illustration below (from Wikipedia) of Delias aganippe (a notable exception in Australia is Delias aruna, which has the upper surface of the wings bright orange-yellow). Nevertheless, they appear to be among the more colourful members of the generally modest family Pieridae, which may be best known to many of you by the cabbage whites of the genus Pieris.


There are a large number of species of Delias (I couldn't be bothered actually counting them up) placed in 23 species groups. If you want to know exactly what they all are, I'd recommend looking at Les Day's exceedingly thorough site dedicated to Delias at http://www.delias-butterflies.co.uk/. The caterpillars feed on mistletoes (hence the title of this post), which makes them notable from a conservation point of view - many mistletoes are rare and/or endangered (their thick, fleshy leaves make them very attractive to browsers), and if a species of mistletoe goes extinct then its specialist herbivores go extinct as well. While most members of Pieridae lay eggs singly, Delias lay their eggs in large clusters. The caterpillars come in a range of colours, and have long white hairs - the photo here from Wikipedia of Delia eucharis caterpillars shows both the hairs and their gregarious habits. The chrysalis is brightly-coloured, usually bright yellow or orange.

Many species of Delias have seasonal varieties, with the dry-season or winter variety being darker above, or having the underside more cryptically coloured. Studies in other Pieridae have shown that rather than being genetically determined, these variations appear to be determined by the photoperiod the larva is exposed to during development, specifically during the third and fourth instars (Hoffmann, 1973). Experimental manipulation of photoperiod exposure has even been able to induce 'seasonal variation' in species that are univoltine (only one generation per year) instead of multivoltine (multiple generations per year - Shapiro, 1977).

REFERENCES

Braby, M. F. 2004. The Complete Field Guide to Butterflies of Australia. CSIRO Publishing: Collingwood (Australia).

Hoffmann, R. J. 1973. Environmental control of seasonal variation in the butterfly Colias eurytheme. I. Adaptive aspects of a photoperiodic response. Evolution 27 (3): 387-397.

Shapiro, A. M. 1977. Evidence for obligate monophenism in Reliquia santamarta, a Neotropical-alpine pierine butterfly (Lepidoptera: Pieridae). Psyche 84: 183-190.

Diversity and Distribution of Tropical Lepidoptera: a bit of cross-purposes

This is the first of the commentaries I promised yesterday. While the rest of the world seems to have become bizarrely fixated on some fossil find from some minor mammalian clade, yesterday's Nature also included two far more interesting papers on the distribution of herbivorous insects in tropical rainforests.

"Short-range endemics" is a bit of a buzzword here in Australia at the moment, referring to the pattern in a number of taxa, especially invertebrates, of large numbers of closely-related species of exceedingly restricted distributions (a study one of my supervisors recently conducted of subterranean arachnids called schizomids found that almost each individual mesa that housed schizomids housed its own individual species). The current papers could be very interesting in light of short-range endemism. They are also very interesting in light of the overall question of why the tropics are so hyperdiverse compared to higher latitudes.

As I said yesterday, the two papers differed somewhat in their conclusions (but more on that later). First off, the paper by Novotny et al. looked at diversity within a 75,000 square kilometre area of lowland rainforest in Papua New Guinea. While the area of rainforest was continuous, the Sepik River does cut through it, and some of the plant species compared had quite restricted distributions. Novotny et al. looked at Lepidoptera (caterpillars), ambrosia beetles (Scolytinae and Platypodinae) and Tephritidae (fruitflies) and compared the species found on each host plant genus investigated between eight sites. They found that there did not appear to be a significant change in species composition from one area to another - the species that were found on Ficus at one site were pretty much the same as those found on Ficus at another, over the entire area investigated. The Sepik River did not appear to be a major barrier to dispersal.

At the same time, Dyer et al. looked at average host specificity of herbivorous caterpillars at different latitudes in the Americas. They found that tropical species tend to have much higher host specificity than temperate species. This is in direct contrast to a paper Novotny et al. published last year, that found no significant difference in host specificity between taxa in Papua New Guinea and Europe. Instead, Novotny et al. attributed the increase in insect diversity in the tropics to the shear increase in number of potential host plant species.

So on the one hand we have a paper that seems to argue for wide distributions of tropical taxa, on the other we have one that argues for high host specificity (and hence, one suspects by implication, more restricted distributions). After reading through the papers, I don't think the conflict is actually that strong, as I'll explain in a moment.

Dyer et al. do offer some suggestions for why their results were different to Novotny et al.'s last year. One is that there may be actual difference between the Old World and the Americas. I just can't see that being significant - while there are some differences in which families are dominant in each hemisphere, there are many families that are present in both, and the latitudinal influences are still similar in each - far north it's still colder. The other factor that I think is far more likely to be significant is that Dyer et al. looked at a far greater range of host species than Novotny et al - the latter looked at 18 species in each area, while Dyer et al. looked at up to a maximum of 281 species in Costa Rica. Most significant of all, though, is that Dyer et al. looked at only one potential host species per genus per area. This would tend to bias their results towards higher measurements of host specificity, but is arguably more informative. If you compare a tropical species that feeds on three species of Ficus to a temperate species that is recorded feeding on one species each of Euphorbia, Quercus and Fagus, the temperate species should obviously be regarded as far less host-specific in light of the far greater phylogenetic distance separating its hosts. Unfortunately, a solely numerical metric will not distinguish the two.

Which brings us back to my point that the two Nature papers are not as contradictory as they first appear. The paper from Papua New Guinea compared species from different areas of the same genus. It looked at a different level of resolution than the Dyer et al. paper. As for the implications of the Novotny et al. paper for short-range endemism, the obvious point seems to be that most short-range endemics appear in taxa such as arachnids, myriapods and troglobites - taxa with relatively low dispersal capabilities. In contrast, Novotny et al. looked at insects - winged, and therefore one would expect able to disperse over greater distances more easily, so long as a suitable host plant was present when it got there. In support of this, spiders that disperse by a 'ballooning' stage when young (such as Nephila, the golden orb weaver) tend to be far less diverse with individual species found over much greater areas.

Of course, the number of potential host species in the tropics is still doubtlessly a factor. But this just begs a further question. If insects are so much more diverse because the plants are so much more diverse - then why are the plants more diverse?

PS. I really feel that I should mention that the study by Novotny et al. had a large proportion of the fieldwork conducted by locally trained staff, a number of whom are in the author list below. With the low levels of scientific education available in third world countries, the organisers of this study are to be commended on this front.

REFERENCES

Dyer, L. A., M. S. Singer, J. T. Lill, J. O. Stireman, G. L. Gentry, R. J. Marquis, R. E. Ricklefs, H. F. Greeney, D. L. Wagner, H. C. Morais, I. R. Diniz, T. A. Kursar & P. D. Coley. 2007. Host specificity of Lepidoptera in tropical and temperate forests. Nature 448: 696-699.

Novotny, V., P. Drozd, S. E. Miller, M. Kulfan, M. Janda, Y. Basset & G. D. Weiblen. 2006. Why are there so many species of herbivorous insects in tropical rainforests? Science 313: 1115-1118.

Novotny, V., S. E. Miller, J. Hulcr, R. A. I. Drew, Y. Basset, M. Janda, G. P. Setliff, K. Darrow, A. J. A. Stewart, J. Auga, B. Isua, K. Molem, M. Manumbor, E. Tamtiai, M. Mogia & G. D. Weiblen. 2007. Low beta diversity of herbivorous insects in tropical forests. Nature 448: 692-695.