Bulbophyllum Grace Thoms traps a fly

The flower of this Bulbophyllum proved irresistible to a local fly.  The hinged lip pressed the fly into the stigmatic cavity.  The fly got stuck in place due to the stigmatic fluid.  The fly was struggling and trying to escape but without success.  Very gently I released it, the fly fled with admirable alacrity.  So far no other insect has become trapped in the flowers.  I suspect the flower is producing a fragrance with a distinct fecal tone for the flies to be so interested in the them, but so far I haven't been able to detect any fragrance at all.

A tale of manipulation, desire and grisly violent death on a Bulbophyllum flower

Do you want a hug?  Seem to say this crab spider
sitting on top of a Bulbophyllum flower lip.

You can see the spider sitting on the lip of the flower

When the spider would go away from the lip
 the fly would move to it.

The spider tries to hide from me.

A fly, not the fly in the previous photos, became dinner.

Yesterday I noticed that a Bulbophyllum inflorescence had become a focus of fly activity.  I decided to take a few photos but instead of the usual 18 to 55 mm zoom lens I use, I decided to try to see if I would be able to get some decent shots using my 100mm macro lens.  This macro lens is wonderful to take photos of still subjects such as orchid flowers but a real nightmare to use with subjects that keep moving even if they only move a few millimeters when you are focusing.

To my surprise the fly that was over one of the leaves of the orchid was strangely indifferent to my presence.  Yes, it would fly away if I got too close, only to return quickly if I retreated a bit.  I was able to get within a few inches of the fly and take the closest macro shots of a fly I have ever gotten.  I wondered whether the brain of the fly was somehow addled by the scent of the flower but what happened the next day disproved that theory.

In the morning, a fly, maybe the same one, was sitting on the flowers.  But there was a new visitor on the flowers.  It seems I was not the only one to notice that flies were being attracted to the flowers.  A small green crab spider had taken residence on one of the flowers.  The fly seemed aware of the presence of the spider as it would not go near it.  When I started taking photos of spider, it became agitated and ran away. It tried to hide in the base of the inflorescence.  I decided to leave the spider alone for a while.  The fly, when the spider had retreated, went all over the place where the spider had been.  I could see the spider was watching the fly, which was much larger than the spider, the fly activity was probably a very powerful lure to the spider to return to the flower.

Several times I came near the spider with the camera and every time the spider retreated to the perceived safety of the inflorescence.  But in the end, the spider decided to (metaphorically of course) grit its teeth and tolerate my presence.  The spider would sit on top of the lip of the orchid with its front legs outstretched, ready to grab any insect foolhardy enough to come close.  The theory that the fly was somehow befuddled by the orchid fragrance was disproved by the fierce way the fly would attack any other fly that would come close to the flowers.  I saw it confront aggressively and chase away, two other flies that alighted on the flowers.   In a perverse way, the strong allure that the flowers had for this fly was preventing them from being pollinated.  The large black fly had the wrong weight to properly activate the hinged mechanism of the orchid lip that ensured that the fly received the pollen.  The fly was fiercely preventing any fly of the appropriate size to affect pollination from sitting on the lip of the flowers.  So paradoxically even thought the flowers were surrounded by flies but not one flower had lost its pollinia or had been pollinated.

By the afternoon the flies had left and the spider remained sitting on the flower.  At 5:30 pm I went to take a look and discovered that the spider had been successful in catching a fly, just not the big flies that were around the flower in the morning.   I wonder if the spider will be there tomorrow, the flowers are getting close to senescence and will probably last only two or three more days.  Tomorrow I will again look to see if a new drama of manipulation, desire and grisly death plays itself out in the flowers.

Ponthieva racemosa, the shadow witch, an orchid native of Puerto Rico

Ponthieva racemosa

Inflorescence, top view

A fly with pollinia stuck to its mouth parts

Pontieva racemosa goes by the common name “the shadow witch”, I don’t know the origin of the name but I am sure it is due to its preference for growing in shaded locations.  It has a patchy distribution in the Rio Abajo forest where it can be locally abundant.  When this plant is not in bloom there is little to betray that it is an orchid.   You can sometimes see it in roadside banks among the weeds as a low growing rosette of leaves growing in the shadow under the trees.  Locally it blooms in the winter and all the plants in a location bloom together.  The flowers are green and small.  It is not in cultivation and I have never seen it exhibited in any of our local orchid shows.

A group of Ponthieva racemosa

Bulbophyllum biflorum flower and two flies fighting over it

These flies are usually quite wary as in the garden there are a plethora of predators that think of flies as convenience food. However it seems the smell of this Bulbophyllum biflorum had them entranced to such a degree that they would not move from the flower even when I approached very closely. When I shooed one away the other one would quickly jump on the flower. When both landed on the flower a scuffle ensued and one was thrown from the flower. I could not help but think of two gunslingers that were waiting to see who would make the first move. I have tried to detect a smell but it I can't smell anything. Perhaps other people who have this plant can describe the smell. I assume it is a fecal smell due to the type of fly that is attracted to the flower. Even though ordinarily I would shoo the flies away as to prevent them removing the pollen and causing premature folding of the flowers, in this case I am going to allow the poor blighters some leeway. The truth is that the life of these flies must be one big and smelly pile of s**t, so if they are trying to get their jollies in much pleasanter surroundings I will not be the one to deprive them of the opportunity.