A fleshy flower and a chemical signal
Stapeliads and their relatives belong to the dogbane family, Apocynaceae. Fleshy stems store water, while flowers create an elaborate system of chemical, visual and tactile signals. Flies respond to it while seeking food or a site for offspring development. At the flower centre, their movement is directed towards structures that transfer pollinia. [Meve and Liede 1994] [Bruyns et al. 2014]
Sapromyophily includes different associations with organic matter. A flower may mimic carrion, dung or another substrate attractive to a particular group of flies. The biological meaning of the scent derives from insect ecology, the composition of the volatile mixture and behaviour after landing. These three elements can be studied separately and then compared. [Jürgens et al. 2006]
Four chemical profiles
Jürgens, Dötterl and Meve analysed volatile compounds from fifteen species belonging to eleven genera. Scent was collected by adsorption from air surrounding the flower, and composition identified by chromatography and mass spectrometry. Large differences emerged between species. A high proportion of p-cresol was linked to mimicry of herbivore dung, while predominance of volatile sulphur compounds was linked to carrion or carnivore and omnivore dung. [Jürgens et al. 2006]
Other profiles contained abundant heptanal and octanal or hexanoic acid. The authors interpreted these in relation to animal substrates and urine scent, respectively. This is a chemical and ecological classification. Identifying compounds allows a signal hypothesis to be formulated, whose specific function is then tested through insect responses. [Jürgens et al. 2006]
Scent is produced in osmophores
In Orbea variegata and the Boucerosia indica material studied, Płachno, Świątek and Szymczak described specialised scent-producing tissues. Glandular papillae occur on the corolla surface, with active cells beneath them containing organelles associated with secretion synthesis and transport. Details of the cuticle and intercellular spaces indicate routes of compound release into the surroundings. Intense scent is a product of active floral metabolism. [Płachno et al. 2010]
Orbea variegata. Visibility and spots
In experiments by du Plessis and colleagues, Orbea variegata (in the paper, Ceropegia mixta) attracted flies even when the flower was concealed. Visible flowers, however, received more visits. Models with natural scent showed greater attraction to black than yellow, with no detected effect of size or the presence of spots. [du Plessis et al. 2018]
The most important pollinator in the populations studied was the housefly, Musca domestica, with smaller contributions from blowflies and flesh flies. Insects probed the flower centre, and pollinia attached to their mouthparts. Pollinium removal and subsequent deposition were measured separately, as was fruiting. [du Plessis et al. 2018]
Stapelia hirsuta. Hairs prolong the visit
Shuttleworth and colleagues studied Stapelia hirsuta var. hirsuta (in the article, Ceropegia pulvinata var. pulvinata). The paper, published in June 2026, describes field experiments from 2016. Removing hairs did not change fly arrival frequency, but shortened flower probing time. Hairs therefore help shape the behaviour of an insect already present. [Shuttleworth et al. 2026]
Flower position also proved important. Raising it by one metre reduced visits, while raising it by half a metre did not have this effect. Yellow and burgundy flowers in the population studied were visited similarly. Pollinia were found on Lucilia and some flesh flies, although other flies also visited the flowers. [Shuttleworth et al. 2026]
Edithcolea grandis. Possible wound mimicry
The paper by Meve and colleagues from October 2026 documents pollination of Edithcolea grandis by female Musca xanthomelas in the observed population in Tanzania. These flies use animal dung and secretions, including blood available in wounds. The narrow, recessed flower centre directs their mouthparts towards the gynostegium. [Meve et al. 2026]
The scent of a separately studied flower from a cultivated plant contained compounds including p-cresyl isobutyrate and butyrate, δ-cadinene and α-copaene. The authors proposed mimicry of a wound as an adult fly feeding site. This hypothesis links flower structure, scent composition and pollinator biology. Detection of a single egg indicates that signals associated with egg laying may overlap with it. [Meve et al. 2026]
From attraction to pollination
Success requires successive events, including insect arrival, appropriate probing, removal of a pollinarium and deposition of a pollinium in the next flower. Each stage faces different constraints. In Orbea lutea subsp. lutea, an important filter is the size of the passage in the corona. In the Stapelia hirsuta studied, hairs affect contact duration. Comparing these papers shows how similar scents can lead to specialised pollination through different routes. [Shuttleworth et al. 2017] [Shuttleworth et al. 2026]
Prepared from scientific publications. Accepted names were checked in POWO on 9 October 2026.
Floral biology and pollination in stapeliads — new results and a literature review
Meve U., Liede S., Floral biology and pollination in stapeliads — new results and a literature review, Plant Systematics and Evolution, 1994, 192(1–2):99-116, doi: 10.1007/BF00985911
The study describes the structure of the gynostegium, pollinia and attachment apparatus, and the mechanics of stapeliad pollination by flies. It combines observations with a review of earlier reports. It discusses scent, flower surfaces, nectar and the fit of insect mouthparts to floral structures.
The chemical nature of fetid floral odours in stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae)
Jürgens A., Dötterl S., Meve U., The chemical nature of fetid floral odours in stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae), New Phytologist, 2006, 172(3):452-468, doi: 10.1111/j.1469-8137.2006.01845.x
A GC-MS analysis of the scents of fifteen species belonging to eleven stapeliad genera. It distinguishes groups dominated by sulphur compounds, p-cresol, aldehydes or hexanoic acid. The authors interpret the chemical profiles in relation to mimicry of different food sources and sites for fly larval development.
Entering through the narrow gate: A morphological filter explains specialized pollination of a carrion-scented stapeliad
Shuttleworth A., Johnson S. D., Jürgens A., Entering through the narrow gate: A morphological filter explains specialized pollination of a carrion-scented stapeliad, Flora, 2017, 232:92-103, doi: 10.1016/j.flora.2016.09.003
The field study of Orbea lutea subsp. lutea combines fly observations, morphometry, scent analysis and measurements of pollination success. In the population studied, pollinia were carried by females of one Atherigona species whose heads fitted between the corona lobes. The paper shows how a mechanical pollinator filter works.
Pollination of the “carrion flowers” of an African stapeliad (Ceropegia mixta: Apocynaceae): the importance of visual and scent traits for the attraction of flies
du Plessis M., Johnson S. D., Nicolson S. W., Bruyns P. V., Shuttleworth A., Pollination of the “carrion flowers” of an African stapeliad (Ceropegia mixta: Apocynaceae): the importance of visual and scent traits for the attraction of flies, Plant Systematics and Evolution, 2018, 304(3):357-372, doi: 10.1007/s00606-017-1481-0
The study of Orbea variegata, described as Ceropegia mixta, examines pollinators, scent composition and experiments with the visibility and colour of model flowers. Scent also attracted flies to concealed flowers, while visibility increased visits. The size and presence of dark spots did not change the frequency of visits to the models.
Hairy, hairy quite contrary: Pollination and functional floral traits in a hirsute carrion-scented stapeliad
Shuttleworth A., du Plessis M., Bruyns P. V., Johnson S. D., Hairy, hairy quite contrary: Pollination and functional floral traits in a hirsute carrion-scented stapeliad, TAXON, 2026, 75(3):e70174, doi: 10.1002/tax.70174
Field experiments on Stapelia hirsuta var. hirsuta, treated in the paper as Ceropegia pulvinata var. pulvinata. The authors analyse scent, colour, hairs and the height at which flowers are presented. Removing hairs shortened probing time, and raising flowers by a metre reduced the number of visits.
Large-flowered stapeliad Edithcolea grandis (Apocynaceae: Asclepiadoideae) is pollinated by dung- and blood-feeding African face flies (Muscidae: Musca xanthomelas)
Meve U., Heiduk A., Dötterl S., Liede-Schumann S., Large-flowered stapeliad Edithcolea grandis (Apocynaceae: Asclepiadoideae) is pollinated by dung- and blood-feeding African face flies (Muscidae: Musca xanthomelas), TAXON, 2026, 75(5):e70251, doi: 10.1002/tax.70251
Observations of an Edithcolea grandis population in Tanzania document pollination by female Musca xanthomelas. A separate scent analysis was conducted on a flower from a plant cultivated in Germany. The paper describes unusual volatile p-cresyl esters and develops the hypothesis of wound mimicry as a fly food source.
Evolution of the stapeliads (Apocynaceae–Asclepiadoideae) – repeated major radiation across Africa in an Old World group
Bruyns P. V., Klak C., Hanáček P., Evolution of the stapeliads (Apocynaceae–Asclepiadoideae) – repeated major radiation across Africa in an Old World group, Molecular Phylogenetics and Evolution, 2014, 77:251-263, doi: 10.1016/j.ympev.2014.03.022
An analysis of 192 stapeliad species based on nuclear and plastid markers. It reconstructs repeated radiations in Africa and relationships between lineages with very different floral structures. The results challenge the monophyly of some traditionally recognised genera.
Can a stench be beautiful? – Osmophores in stem-succulent stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae-Stapeliinae)
Płachno B. J., Świątek P., Szymczak G., Can a stench be beautiful? – Osmophores in stem-succulent stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae-Stapeliinae), Flora, 2010, 205(2):101-105, doi: 10.1016/j.flora.2009.01.002
A microscopic study of osmophores in Orbea variegata and Boucerosia indica. It describes glandular papillae, subepidermal cells, organelles and routes of secretion release. It explains the anatomical basis for the intense scent of living flowers.
