 |
| a settling moth, the bindweed or four-spotted moth, Tyta luctosa Denis & Schiffermüller (Noctuidae) on a cosmos (Cosmos) flower |
Settling moths are known from the moth families Noctuidae, Geometridae, Crambidae, Hepialidae, Zygaenidae, Pterophoridae, Gracillariidae, and Prodoxidae. Probably moths from other families also pollinate, but it hasn't been reported. Moths as a group are nocturnal, camouflaged so they can sleep safely by day, and many are difficult to identify to scientific name. Often researchers find pollinating moths not by watching them pollinate the flowers, but by attracting them to a light, capturing them, and looking to see if they are carrying pollen. Then the pollen has to be identified. But whether the moth actually pollinated, carrying pollen from one flower of a species to another of the same species, has to be inferred. Maybe the moth only went to one flower, just before being lured to the light. Studying moths as pollinators is difficult.
Some plants, though, are well known to be pollinated by settling moths. Plants of the genus Silene, campions (carnation family, Caryophyllaceae), widely distributed across the Northern Hemisphere, worldwide, are pollinated by settling moths. Many species have white or pink flowers, the flowers open at or after dark, and they release a pleasant, in some cases, strong, scent into the dusk. White campion, Silene latifolia, shown below, is a good example of the group. While settling moths have been shown to pollinate them, e.g. Europe's silver-Y (Autographa gamma Linnaeus, Noctuidae), they are also pollinated by sphinx moths (which hover) and a variety of bees. The details vary with the place and the species; some campions are mainly pollinated by settling moths, others are visited by settling moths but bees or sphinx moths provide equally good pollination.
 |
| well-known moth pollinated plant white campion, Silene latifolia |
Just as other pollinators go to plants whose flowers indicate moth pollination, moths will visit and pollinate flowers that are not obviously the right shape or color, for example the four-spotted moth visitng Cosmos in the first photo above.
In the late 1970s as a newly hired plant ecologist at the University of Nebraska-Lincoln, I took my book-learning into the prairie and spotted a long-tubed white-flowered plant that became more visible in the evening and emitted a lovely scent about dark, the sweet sand-verbena, Abronia fragrans (Nyctaginaceae). Aha! I postulated it was moth-pollinated.
Settling moths also pollinate flowers than are not white or tubular. Glochidion (spurge family, Euphorbiaceae) is a large genus of small trees in Asia with small, open pale flowers, suitable for moths but rather generalized (link); the moths whose larvae grow on its seeds are its most effective pollinators.
Moths that might be settling moth pollinators are so numerous that there are many we know little about. Since they pollinate by night, we rarely see them. Nevertheless for some plants they are well-known to be important pollinators. Try to notice plants with the fragrant white tubular flowers that are well-suited to moths and watch for the moths, especially as it gets dark. A mysterious but very cool group of pollinators.
 |
| flower of sweet sand-verbena, Abronia fragrans |
The literature had no reports of its pollination, so Myra Fredricks and I went out to catch a pollinator. It was pretty discouraging, hanging around in the darkness, barely seeing the flowers, hoping to glimpse a bit of movement. I was expecting a sphinx moth, which is pretty big, likely dark against the white flowers, and hovers, often audibly. We never saw a sphinx moth, but we observed and then caught a noctuid moth, Nycterophaela luna (Morr.)
 |
| Nycterophaela luna |
and found pollen on its proboscis (the dots in the close-up below).
 |
| Nycterophaela luna showing pollen on proboscis |
We were pretty pleased. But, although our little study adds to the list of moth-pollinated plants, it hardly begins to answer all the questions one has about pollination of sweet sand-verbena. Maybe it is pollinated by many other moths. Some of the campions (Silene species) have been shown to have four or five settling moths that pollinate them. A related species, Abronia macrocarpa in Texas, is pollinated by both settling moths and sphinx moths. A pink Abronia, A. umbellata, had many more flower visitors by day but the effective pollination occurred at night, the nocturnal pollinators including moths in the families Geometridae, Noctuidae, and Pyralidae as well as a sphinx moth (Sphingidae).
The relationships of pollinating settling moths to the plants they pollinate can be complex. Some of the same moths that pollinate Silene species feed on them as caterpillars. Many of the settling moth pollination studies in the literature describe moths that both feed on and pollinate the plant, including the famous yucca-moth yucca mutualism and the senita cactus and its pollinating pyradid moth (see other blog post).
Groups of plants that include species with flowers pollinated by settling moths include clematis (Clematis), campions (Silene), pinks (Dianthus), soapwort (Saponaria), columbines (Aquilegia), evening primroses (Oenothera), jasmins (Jasminum), morning glories (the white ones, Ipomoea), sand verbenas (Abronia) and diverse cacti. Some are visited by just by settling moths probably most by both settling moths and hovering moths (sphinx moths).
 |
| evening primrose, probably pale evening primrose Oenothera pallida (evening primrose family. Onagraceae) on a cloudy morning so the flowers that opened just after dark were still open in daylight (western Nebraska) |
Moths that might be settling moth pollinators are so numerous that there are many we know little about. Since they pollinate by night, we rarely see them. Nevertheless for some plants they are well-known to be important pollinators. Try to notice plants with the fragrant white tubular flowers that are well-suited to moths and watch for the moths, especially as it gets dark. A mysterious but very cool group of pollinators.
 |
| an unknown moth |
References
Doubleday, L.A. D. and C. G. Eckert. 2018. Experimental evidence for predominant nocturnal pollination despite more frequent diurnal visitation in Abronia umbellata (Nyctaginaceae). Journal of Pollination Ecology. 22: 67-74. link (Accessed 3/8/25)
Kato, M., A. Takimura and A. Kawakita. 2003. An obligate pollination mutualism and reciprocal diversification in the tree genus Glochidion (Euphorbiaceae). PNAS (Proceedings of the National Academy of Science, USA). 100: 5264-5267. link (Accessed 3/8/25)
Keeler, K.H. and M.S. Fredricks. 1979. Nocturnal pollination of Abronia fragrans (Nyctaginaceae). Southwestern Naturalist. 24: 692-693. link (digital commons, UNL) (Accessed 3/8/25)
Kephart, S., R. J. Reynolds, M. T. Rutter, C. B. Fenster and M. R. Dudash. 2006. Pollination and seed predation by moths on Silene and allied Caryophyllaceae: evaluating a model system to study the evolution of mutualisms. New Phytologist. 169: 667-680. link (Accessed 3/8/25)
Williams, P. S., L. Muliani and G. K. Janssen. 1994. Pollination biology of Abronia macrocarpa (Nyctaginaceae), an endangered Texas species. The Southwestern Naturalist 39: 336-341.
Kathy Keeler
A Wandering Botanist
More at awanderingbotanist.com
Join me on Facebook: https://www.facebook.com/AWanderingBotanist
No comments:
Post a Comment