Floral biology of Hesperantha (Iridaceae: Crocoideae): How minor shifts in floral presentation change the pollination system. P Goldblatt, I Nanni, P Bernhardt, JC Manning 2004 Annals of the Missouri Botanical Garden 91: 186–206.

has this interesting insight (I might mention that it follows a few paragraphs debunking floral syndromes, so perhaps a bit of salt might be necessary):

As described in the genera Babiana, Gladiolus, and Lapeirousia, tubular flowers that are

• pink to the human eye (e.g., Heserantha. brevicaulis, H. grandiflora, H. huttonii, H. woodii) are most likely to be pollinated by the Nemestrinidae: Prosoeca ganglbauri and Stenobasipteron wiedemannii.
• intense blue to purple flowers (e.g., H. latifolia, H. oligantha) are pollinated by Prosoeca peringueyi or Prosocea sp (undescribed).
• Pale yellow to cream, tubular flowers are more likely to be pollinated by long-proboscid Tabanids in the genus Philoliche.

Rhinomyiophily is largely a Cape Flora phenomenon. Well documented by Vogel in 1954, a consists of a guild of flies with long beaks (some carried forward like spears, others straight down like brooms and others with them tucked below and between their legs) in several families - mainly Bombylidae, Tabanidae and Nemestrinidae.

Plants pollinated by these flies have long, very thin tubes, with flags at the front (distal) end to attract the flies and - just as importantly - guide the tongues into the flowers. The flies have to hover in front of the flowers in order to insert their beaks. They tend to be big, to fly in spring, on hot, less windy, days around midday.

This is a fascinating Syndrome: here we collect both the flies and the flowers.
To contribute, please add the project "Rhinomyiophily" to your observation. This project is restricted to southern Africa.