Tag Archives: Moths

A new study shows that even short-tubed flowers can specialise on hawkmoths as pollinators

Of all of the “classical” pollination syndromes, flowers that are hawkmoth pollinated have one of the highest levels of predictability. If a flower is pale in colour, opens at night, is highly scented, and possesses a long tube at the bottom of which is a supply of nectar, there’s a very high likelihood that it’s pollinated by long-tongued hawkmoths (Sphingidae).

Indeed, one of the foundational stories about the development of our understanding of how pollination systems evolve, relates to Charles Darwin, the long-tubed orchid Angraecum sesquipedale and the hawkmoth Xanthopan morganii praedicta.

Fast forward 160 years and we now know that pollination syndromes are more complex than 19th and early 20th century scientists imagined – see my recent book Pollinators & Pollination: Nature and Society for a discussion of this topic. That’s not surprising because, as I point out, we probably have data on the interactions between plants and their pollinators for only about 10% of the estimated 352,000 species of flowering plants. There’s still much to be discovered!

As an example of how our understanding of specialised flower-hawkmoth interactions is developing, consider this recent study that I’ve just published with my Brazilian colleague Felipe Amorim and other collaborators. In it we have shown that, contrary to expectations, a species of Apocynaceae (Schubertia grandiflora) with a relatively short floral tube can specialise on hawkmoths with much longer tongues than we might predict.

The full reference with a link to the study is shown below, followed by the abstract. If you would like a PDF, please drop me a line via my Contact page:

Amorim, F.W., Marin, S., Sanz-Viega, P.A., Ollerton, J. & Oliveira, P.E. (2022) Short flowers for long tongues: functional specialization in a nocturnal pollination network of an asclepiad in long-tongued hawkmoths. Biotropica https://doi.org/10.1111/btp.13090

Abstract:

Since Darwin, very long and narrow floral tubes have been known to represent the main floral morphological feature for specialized long-tongued hawkmoth pollination. However, specialization may be driven by other contrivances instead of floral tube morphology. Asclepiads are plants with a complex floral morphology where primary hawkmoth pollination had never been described. We detailed here the intricate pollination mechanism of the South American asclepiad Schubertia grandiflora, where functional specialization on long-tongued hawkmoth pollinators occurs despite the short floral tube of this species. We studied two plant populations in the Brazilian Cerrado and recorded floral visitors using different approaches, such as light-trapped hawkmoths for pollen analysis, direct field observations, and IR motion-activated cameras. Finally, using a community-level approach we applied an ecological network analysis to identify the realized pollinator niche of S. grandiflora among the available niches in the pollinator community. Throughout a period of 17 years, long-tongued hawkmoths were consistently recorded as the main floral visitors and the only effective pollinators of S. grandiflora. Flowers rely on highly modified corona and gynostegium, and enlarged nectar chambers, to drive visitors and pollination mechanism. Despite its relative short-tube, network analysis placed S. grandiflora in the module including exclusively long-tongued hawkmoth pollinators and the most phenotypically specialized sphingophilous plants in the community. These results represent the first example of functional specialization in long-tongued hawkmoths in an asclepiad species. However, this specialization is uncoupled from the long floral tubes historically associated with the sphingophily syndrome.

Last year’s mother, this year’s child: cinnabar moths in the garden

2019-07-06 11.48.35

Most summers we have a small colony of cinnabar moths (Tyria jacobaeae) reproducing in the garden.  The garish yellow-and-black caterpillars feed on species of ragwort and we leave a patch of common ragwort (Jacobaea vulgaris) to grow in the lawn.  The caterpillars eat for a few weeks, virtually destroy the ragwort, and in the process accumulate alkaloids from the host plant into their bodies.  This renders them toxic in much the same way as monarch butterflies accumulate toxins from their Asclepias food plants – see my recent post about the Monarchs and Milkweeds workshop.  Hence the stripes to warn birds of their unpalatability.

Ragwort is a much-maligned plant, hated by those with horses and livestock, and subject to a largely hysterical campaign of eradication – see here for example.   However John Clare clearly appreciated its virtues in a poem dedicated to the plant:

Ragwort, thou humble flower with tattered leaves
I love to see thee come & litter gold,
What time the summer binds her russet sheaves;
Decking rude spots in beauties manifold,
That without thee were dreary to behold.

The full text of the poem can be found here.

Once they have fed their fill, the caterpillars dig themselves into the soil to spend twelve months or so underground as pupae, before emerging as gorgeous adult moths, advertising their toxicity with a different colour scheme.

The adults live for a few weeks at most, during which time they feed on nectar, mate, lay eggs and die.  This (unposed) photograph that I snapped on my phone in the garden yesterday just about sums it up: an exhausted mother has laid her last batch of eggs then died, while a nearby young caterpillar munches away on the ragwort.  And so the generations pass.

Cinnabar caterpillars on ragwort

Another new garden pollinator record – Lunar Hornet Moth

Lunar Hornet Moth cropped

Following on from last week’s post about the Ashy Mining Bee, here’s yet another new record for our garden that I spotted yesterday – the Lunar Hornet Moth (Sesia bembeciformis), one of the Clearwing Moths (family Sesiidae).  It’s a fabulous example of Batesian Mimicry in which a harmless species (the moth) has evolved to resemble a more dangerous or toxic species, in this case large wasps or hornets.  I certainly had to look twice when I saw it!  

These moths do sometimes visit flowers such as umbellifers though the shot below is posed: the moth flew out of my hands as I was moving it and landed on this cultivated geranium.  The larvae feed on sallow and willow (Salix spp.) which we don’t have in the garden, but there’s lots in and around this part of the town.

Looking at the NBN Atlas account for the species I think that this may be a first record for Northampton town itself, though it is recorded out in the county.

Lunar Hornet Moth on GeraniumP1040014