Extra floral nectaries on Catasetum?

[Connie Star]

I acquired a Catasetum csm Dentagranum in February from Sunset Valley Orchid, my first one in the US, having previously grown a Cynoches in Costa Rica. It’s doing beautifully with multiple buds along a raceme. My husband who is very knowledgeable about insect/plant interactions noticed some small 1/4 “ ants, and that each one seemed to be doing something at the base of a bud, many of which (buds) had a single small white dot. Although the plant is plenty big, the insects are so tiny that photos are impossible, and even with a hand lens we couldn’t make out if these were extra floral nectaries. Some plants in the tropics provide these, or protein containing Beltian bodies to attract ants that then protect the plant from other herbivores. Anybody know?

[Louis_W]

All of my cattleyas seem to exude a drop of honeydew at the base of the bud and at the tip of the bud. I dont think this is the same substance as nectar but it is very sweet. I think there is just excess sugars that the plabt has to get rid of for whatever reason. These areas turn white when the sap dries and cryatalizes a little bit too

I bet the ants are feeding on these sugars, and perhaps in nature they would mount some sort of protection for the plant.

[Connie Star]

Yes, I know about the honeydew and have seen it on various parts of my orchids. But I know that some non-orchids provide specific organs where the honeydew is located often at the base of a leaf or other vulnerable part of the plant. I just don't know if this is a phenomenon of some orchids.

The picture shows ants enjoying them on an Acacia

[Louis_W]

It seems like a short leap from natural honeydew excretion to ant partnership. I bet a lot of orchids have an early-evolution relationahip with ants! Not to mention the parasitic insects that go after them like scale and mealybugs

Myrmecophila is a genus which has hollowed pseudobulbs specifically for ants.

Judging from your photo, are you also a bird watcher?

[Connie Star]

Originally Posted by Louis_W

It seems like a short leap from natural honeydew excretion to ant partnership. I bet a lot of orchids have an early-evolution relationahip with ants! Not to mention the parasitic insects that go after them like scale and mealybugs

Myrmecophila is a genus which has hollowed pseudobulbs specifically for ants.

Judging from your photo, are you also a bird watcher?

Is the Pope Catholic? I am a long-time serious birder although I still consider myself a very experieinced beginner. Also a bird photographer, as is my amateur entomologist, dendrologist husband (he's not on OB)

I know about myrmecophila and would like to have one. Sometimes the ant genus has to be specific to the plant though. The ants on the acacia are a genus called Azteca

If your interested in the subject, my husband and I have a presentation on ants, plants, and birds. I could probably figure out a way to share it with you on Google Drive. I'll post some photos from it.
White Tipped Sicklebill hummingbird seen once and unfortunately could not get a picture of it on a Heliconia.
Euglossine bees on a Cynoches orchid, from the seasonally dry Guanacaste province of Costa Rica
Pair of Fiery Billed Toucans and a pair of Mot-Mots, just for fun. We should have a forum for interactions between orchids and pollinators or other animals that interact with them

[Louis_W]

Nice photos! Ive been a birder all my life! Im relatively casual about it but ive had the pleasure of looking for birds and plants all over the world.

Id love to see your presentation. Is it on simbiotic relationships?

[SG in CR]

I've not observed any nectaries or other bits that the ants feed on specifically on my Catasetums. But you are right that the inflorescences attract ants. Catasetum maculatum is entering the blooming season now and several of them that have a constant presence of mean little ants on the buds. My guess is that they are exuding honeydew. It's something I've observed on quite a few orchids such as Encyclias and Cohniella.