Acineta Season is Here

Acineta mireyae flowering in April in the Orchid Display House

The petals are lightly spotted with maroon

Removing one petal and one sepal allows a lateral view of the lip

A longitudinal section through the lip

The lip in dorsal view with the column removed

This has been a terrific year for our acinetas. So far, in April and May, we've had at least a half dozen plants in four different species in bud and flower. Most likely it's because last year we moved them to a brighter drier cooler location for the growing season. It's so gratifying to finally see them thriving!

Like other members of the subtribe Stanhopeinae, acinetas are pollinated by fragrance collecting male Euglossine bees. The globose flowers point downward on a pendant raceme like a loose cluster of grapes. The petals and sepals form a hood over the lip and column, creating a tunnel for the bee to enter. The bee scratches at the base of the lip to obtain the liquid fragrance. As he backs out, the sticky base of the pollinarium is applied to his back.

According to Christenson's review of the genus Acineta, in Orchid Digest (2006), the only recorded precise distribution for Acineta mireyae is from the type specimen, collected in Panama. Christenson considered mireyae a synonym of wolteriana.

Identifying our Acineta

Great news: we have a name on our mystery Acineta. And it's not erythroxantha, the name that was on the label when we received it from a Panamanian grower. In order to make the determination, it was necessary to dissect a couple of flowers and send photographs to Dr. Günter Gerlach at Münich Botanical Garden. He was very specific about which floral parts he needed to see. Here is what I sent him.

Shown above, I've removed two lateral sepals and one of the lateral petals in order to show the lip in side view. Each side of the lip has two deep incisions, creating a side lobe. The column is white and partly hidden by the lip.

Next, I made a longitudinal cut through the lip to show it in cross section. The interior has blood red spots. You can see the callus, chair-shaped and white in cross section.

Then, I removed a second flower and cut off everything but the the lip and the ovary. Above, you can see the lip, face up. It is shaped like a shallow scoop. Just above the broadly U-shaped edge of the lip is the callus, which is wide and thin seen from above. The lip and callus are important diagnostic features.

The underside of the lip.

The pollinarium, including two pollinia and a sticky orange viscidium.

This must have been an easy call for Dr. Gerlach, who described this species, Acineta mireyae, in 2003. Additonal photos appear on his amazing Stanhopeinae image data base, where you can compare A. mireyae with some closely related Central American species, Acineta sulcata and Acineta sella-tucica. In fairness to the grower from whom we purchased our plant, I should mention that it was shipped to us in 2002, before publication of the epithet mireyae. Our thanks to Dr. Gerlach for solving this mystery!

Open at last... But what is it?

It's not very often that we flower an Acineta, so there has been tremendous anticipation as the spike of this Acineta erythroxantha has elongated to an astonishing 28 inches. Bud development has been agonizing. ('Slow as Christmas' is the phrase around here.) But at last we have open flowers. And a surprise...

This isn't actually Acineta erythroxantha at all, as the label would indicate. The lip is very different. We received this plant in 2002 as A. erythroxantha from a Panamanian source. Could this be the Panamanian species, Acineta mireyae?

For an answer, I'm turning to Dr. Mark Whitten at University of Florida-Gainesville and Dr. Günther Gerlach at Münich Botanical Garden, rockstars of Euglossine bee-orchid research. Acineta identification is tricky and I want a definitive answer. Dr. Gerlach is the author of the original 2003 publication of  A. mireyae, so I'm sending pictures of these flowers, dissected. We'll see what he says.

Acineta belongs to the Stanhopeinae subtribe, and like Stanhopea, they are pollinated by Euglossine bees of the genus Euplusia.

The waxy fragrant flowers are carried on a pendant raceme. The sepals and petals form a hood around the column, creating a tunnel for the bee to enter. The bee obtains the fragrance by scratching at the base of the lip inside the tunnel. As the bee backs out, the viscidium of the pollinarium is stuck to the bee's scutellum. If the bee enters another Acineta flower, the pollinia are placed on the stigma as the bee backs out, and thus the flower is pollinated.