Hoya krohniaia was published in 2009 as a seperate species from Hoya lacunosa. These two Hoyas may resemble each other at a glance but when viewed side be side there are obvious differences. If you look at the webpages provided by the two links below you can compare some good floral photos side by side. You are lookig for differences in the corona of each species flowers as well as differences in the pollinia or pollen masses. There are some great photos of the pollinia of both species at the bottom of each page.

These two species are close relatives and belong to section Otostemma of which Hoya lacunosa is the type species. If you have any other questions let us know.

Hoya krohniana on GrowingHoyas.com

Hoya lacunosa on GrowingHoyas.com

Mike

So Mike, you agree, they are the same species? Pretty much identical in all respect except for leaf form which is VERY variable in lacunosa.

Lest just say that whatever Mr. Kloppenbugh publishes is often disputed. I am not a taxonomist nor a botanist so my opinion on the matter is not important. I am not knowledgeable enough to be arguing this case. I agree that the plants are very similar but there are differences as well. Of course you would have to examine multiple different specimens and NOT only the ones from growers collections that are more likely than not grown from cuttings of only a few original plants.
I am just so used to taxonomic changes that I tend to just go with the flow. The orchid family has be split up so many times that it's mind-numbing.

Check out the article written by Christine Burton. Her arguments are always well executed and informative and provide the details that are often lacking elsewhere.

Mike

Here is a link that might be useful: Hoya krohniana in The Hoyan

I had already read Burton's comments which was one of the reasons I posted this message. Although she is a venomous she makes some really good points. Supposedly the floral structure in H. australis is extremely variable yet it's one species. I am new to Hoya but not plants. Taxonomist almost always lump plants together. I think that is one reason taxonomist not hobbiest should be describing species and that includes Burton.
Randy