Dendrobium spectabile flower visited by the large carpenter bee Xylocopa mordax

Because I live in the tropics, my orchid collection is all outside.  I live in the middle of an state forest which means that insects of all sorts are plentiful (this means the place is also infested with lots of spiders).  It is a common occurrence for orchids to be visited by insects.  However getting a photo of pollinators is not necessarily easy, as most visits are over in seconds.  I was lucky enough to catch this large carpenter bee in flagrante delicto.

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.

The orchid, the spider and the fly seem like they are playing "cat and mouse",

Last week a Bulbophyllum Elizabeth Ann 'Jean' bloomed in my garden.  It started attracting flies. All the fly activity got the attention of a spider that moved to the flowers.  What I find most remarkable of this is that the flies don't seem to do anything on the flower, they certainly are not pollinating it, or drinking nectar, or even laying eggs, they just sit on the flowers and defends them from other flies with remarkable vigor.  What stimulus the flower is using on the fly to elicit this behavior is a mystery to me, although I suspect it is the fragrance.  The presence of a crab spider make staying on the flower a perilous thing.  The fly seems aware of the spider, however to my surprise, sometimes it gets dangerously close to it.  The spider in question is a crab spider, this spider doesn't make a web, instead, it is build up like a wrestler, with large front legs for grabbing and overpowering prey.  Getting near this spider is the last thing a fly should do, but in this case the flies seems almost desperate to sit where the spider is.  The spider, which preyed on a less alert fly last thursday, was noticeably fatter on friday.  Unfortunately I left home for the weekend and by the time I am back the flowers will have fallen and I will never know if these particular flies survived its obssesion with the flowers.

Bulbophyllum tingabarinum Garay, Hammer, Siegrist 1994, has proven to be wildly attractive to a species of local fly.

The flowers of Bulbophyllum tingabarinum opened about two days ago.  This morning when I walked into the garden I found the flowers had attracted four or five flies that were walking all over the flowers.  I sampled the fragrance and found it stinky and disgusting.  However it appears the flies found it highly attractive.  The fragrance, at least in my orchid is not strong, you have to get close to the flowers to "savor" the full effect.  Most of the flies fled when I moved the orchid to a new location to take photos of the flowers.  But a stubborn one hanged for dear life from the flower and would not leave it even when I got very close with the camera.  The fly seemed particularly taken with the lip, in particular the area just under the column.  This particular fly was too small and light to properly activate the pollination mechanism in the flowers of Bulb, tingabarinum.   The fly seemed to be looking for something in the flower and explored every single part, the sepals, the petals, the lip and even the column.  When I finished taking photos, the fly was still busy and oblivious, moving over the inflorescence.

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

The Bulbophyllum lepidum flowers: Like porn for flies.

Incoming!

My Bulbophyllum lepidum showing several inflorescences

Those flowers look... Hmmm... so alluring and soft and nice smelling

Hey you!  Are you talking to me!

Do you come here often?

Can I buy you a drink?

Your place of mine?  Hey, hey, stop!, stop! !@$%#@$%##^%^%$&$!!!!!!!

 Bulbophylum lepidum is a small orchid that produces inflorescences that resemble half a daisy.  It comes as somewhat of a surprise that a plant in the orchid group will try to resemble a plant in the Compositaceae, the group that includes daisies.  But it all has to do with the need to attract pollinators.  It seems that in this orchid original haunts the local pollinators are strongly attracted to daisies.  Each petal of the “daisy” is an individual orchid flower.  To make things even more interesting the lip of the flowers is hinged and carefully balanced.  If a fly steps on to it, the lip suddenly bends downwards against the column of the flower putting the fly in contact with the adhesive parts at the base of the pollinia.  I have seen unwary flies tumble head first into the flowers of Bulb. lepidum and their reaction never fails to amuse me.

The flowers seem to be mighty attractive to certain small flies.  I have tried to detect what could be so alluring for the flies but so far I have not been able to perceive any fragrance or objectionable smell.  I have to add that the flowers are apparently not attractive all the time, I have only seen activity on them in middle morning.   Whatever attractant the orchid uses to seduce the flies, it is impressively effective.  The flies seem mesmerized by the flowers and become reluctant to fly away from the area.  The fact that my garden is packed with a plethora of reptile, amphibian and arachnid predators that view these insects as flying sandwiches, make this detail even more amazing.   The flies give the impression that they are observing the flowers with the intensity and attentiveness that humans usually reserve to porn, boxing events and lottery drawings.   This disregard for the proximity of potential danger, in which the flies throw caution to the wind, has allowed me to take surprisingly close photos of the flies with my point and shoot camera.  But let’s explain what happens when a fly gets land of a flower.

The flies land on the lip of the flower and then proceed to orient themselves over the long axis of the flower.  Then they slowly move closer to the base of the flower and to the lip.  This may take some time and may be preceded by several flights around the flower as the fly react to alarming stimuli or to other flies buzzing nearby.  Eventually some of the flies step into the lip and are flipped against the column. 

The sudden flip into the column is a startling and frightening event for the flies and you can hear them buzzing loudly and wagging their legs violently.  With only one exception all the flies that have gone through this ordeal have extricated themselves from the flower quickly and flown away with great alacrity so that I have lost them from sight.  On the single case I was able to make observations after the fly had fallen into the flower, I could see the yellow pollinia in the back of the fly.  The fly with the pollinia stood still for a while and then flew away, apparently none the worse for having the pollinia on its back.

Of all my Bulbophyllum this species is the most hardy and undemanding.  It has been growing in the same tree fern pole for the last six years and has covered most of it.  It blooms faithfully for several months every year.  Because it has many pseudobulbs that bloom following their own particular time table the plant has flowers intermittently over a period of months instead of a single flush of many inflorescences at the same time. Each inflorescence last only a few days, they last even less time if they are damaged by strong rain.

My plant is fertilized with 20-20-20 at the rate of one teaspoon per gallon every week during the growing season.  I don’t fertilize if the plant is not producing new growth.

It is grown in what is called “Cattleya light” conditions, which is stronger than for most of my other Bulbophyllums which like more shade, but suits this species fine.  My plant grows better under brighter light and blooms more often.  It gets watered every day when the weather is hot to avoid dehydration.  The rest of the year it can grow fine watered two times a week, but remember I live in a tropical country with a high degree of environmental humidity.

Temperatures locally fluctuate during the year from 65F at night in winter to 95 during the day in the height of the summer.  There is a 10F difference in temperature between the day’s high and low temperatures.

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.