Shining a Golden Light on Serpent Eyes   6 comments


Philip Davison. Costa Rica. Blog. Nature Diaries

Ray of Light

This July was probably the wettest that I have experienced in 16 years of living on the Osa Peninsula.  Here at Cabo Matapalo the total rainfall for the month was 38 inches.  But a lot of the rain came in heavy torrential downpours.  We did see a great deal of sun between the downpours.  Also much of the rain fell overnight.  One morning following a night long deluge the sun rose but while still low in the sky it cast rays of light through the tree trunks.  The shafts of light were emphasized by the rapid rising misty droplets creating a heated steam.

Osa Peninsula. Costa Rica.

The early morning sun breaks through.

Close Encounters of the Bird-eating Kind.

Snakes are notoriously hard to find in a tropical rain forest.  There are snakes on the ground and snakes in the trees, there are snakes out at night and there are snakes out during the day but locating snakes can be a thankless task at best and fruitless preoccupation at worst.  Sometimes snake hunters come to the lodge armed to the teeth with knee length leather boots, grab sticks and snake hooks wanting to engage in 24 hours snake hunting trips.  I have to lower their expectations by telling them that they can turn over every log and rock in the forest and they won’t find snakes.  Conversely people come and walk with trepidation on the forest trails in a state of dread in case they happen upon a snake.  Invariably these will be the people who will find them.

Last week while out on the butterfly transect I was walking through a section of forest, handheld recorder in one hand, camera in the other when I noticed a fairly large snake on the forest floor just to the side of the trail.  I stepped off the path to a position in front of the snake which had frozen and was watching me as I sunk slowly to my knees while lifting the camera to my eye.

As well as being hard to find snakes are difficult to photograph due to the linear dimensions of the body.  Unless they are coiled then only the head will be in focus while the rest of the body is either out of shot or too long for the depth of field to accommodate.  As I leaned forward to get my belly on the ground the snake lifted its head and the performance began.

The snake I was looking at was a Tropical Bird-eating Snake, (Pseustes poecilinotus).  It is also known as the Hissing or Puffing Snake as it has a tendency to turn its head sideways while flattening its neck laterally to give the impression of being larger than it actually is.  It whatever it is that is upsetting the snake, in this case me, it will strike out.  I managed to stay out of range as I did not want to risk a bite to the face.  This species is non-venomous but a snake bite in the vicinity of the eyes may not be such a pleasant experience.  However I did manage to get several shots before rising to my feet and continuing on my way while letting the snake go about its business once more.

Pseustes poecilinotus

Tropical Bird-eating Snake, (Pseustes poecilinotus)

Tropical Bird-eating Snakes are one of the larger serpents to be found in this area.  Fully grown they can reach up to 6 feet in length.  The ground color of the body is a pale blue/grey fused with orangey-brown patches.  The lips and lower sides are a brighter orange and quite often with a yellow belly and dark top to the head. As the name suggests their principal prey item are birds, more particularly chicks and eggs taken from nests.  Rodents make up some of the diet and I have seen them eat bats too.

Tropical Bird-eating Snake

Tropical Bird-eating Snake in Threat Pose

Remember if you visit the area it is highly unlikely that you will see a snake and the ones that you may stumble across will probably be non-venomous.  The snakes want as little interaction with you as you will of them and they will make themselves very scarce in short time so it is not something that should detract from the enjoyment of walking the trails.

Pecked Out Eyes

One of the comments that I come across is the eye spots on an Owl Butterfly when the wings are open resemble the eyes of an owl, (or any other large potential predator), and scare off whatever is trying to catch the butterfly.  As I have said previously in this blog it sounds like a good anti predator strategy but fails when put into practice as when the butterfly opens it wings, the spots which are on the ventral surface are then underneath and can’t be seen.

Morpho helenor

Damaged Blue Morpho, (Morpho helenor)

Many predators when aiming to catch, subdue and kill their prey will direct an attack in the area of the eyes because lying behind the eyes is the major part of the central nervous system, the brain.  Destroy the prey’s brain and the battle is over.  So many butterflies have a ruse that will use this attack to their advantage, they create a false eye.  It is usually large and distinct and placed at the trailing edge of the hind wing.  Any bird or lizard taking a peck or bite at the “eye” area will only be rewarded with a tatty piece of wing membrane while the main body of the butterfly makes its escape.

Caligo eurilochus

Damaged Owl Butterfly, (Caligo eurilochus)

With these two butterflies this damage can be seen quite nicely illustrated.  The Blue Morpho, (Morpho helenor), has a line of eye spots down the trailing edge of the upper and lower wing.  As can be seen the wing has already been pecked at and torn in that area yet the butterfly is still capable of flight.  With the Owl Butterfly, (Caligo eurilochus), very obviously the attack was directed against the “eye”.  More often than not, unless it is newly emerged, the Owl Butterflies will be missing this part of the wing when seen in the wild.  It buys the butterfly a second change to locate a mate to partner with and reproduce.

Big-legged Bug

It is thought that the term bug comes from the Old English word for a goblin.  The tern bug when applied zoologically refers specifically to the order: Hemiptera.  This order is divided into two sub orders depending upon the structure of the wings.  The sub order: Heteroptera have the wings divided almost equally into a thick basal part and a thin distal part.  The sub order: Homoptera have the wings completely thin and cellophane-like.

As you can see this Big-legged Bug, (Pachylis tenuicornis), is a heteropteran with wings being clearly divided into two textures. It belongs to the family: Coreidae, the Big-legged or Flag-legged Bugs.  The hind legs are very swollen and stout.  This individual flew past me in an area of grassland where it landed not too far away on the ground.  The thing that caught my eye was the bright red coloration of the body beneath the wings.

Big-legged Bug

Big-legged Bug, (Pachylis tenuicornis)

The Big-legged Bugs when attacked by a predator lift the wings to reveal that bright coloration which warns of an impending defensive measure, notably that it is about to spray from glands an offensively odorous fluid.  The fluid discharges from a gland on the thorax and opens by way of a pore on either side.  The gland has a valve which allows one or the other or both pores to discharge at once.  The cuticle around the pores is sculpted so that when the fluid is sprayed some of it remains on the body providing even further protection.  Thankfully I did not disturb this individual so much as to stimulate such a reaction.

How to Spin a Golden Orb

One of the commonly seen spiders in this area, due to their large size and elaborate webs, is the Golden-orb Spider, (Nephila clavipes).  Its large size and striking black and yellow coloration along with the “furry” legs make it look very dangerous but it is in fact totally harmless to humans.

Nephila clavipes

Female Golden-orb Spider, (Nephila clavipes)

Like just about all other spiders they are carnivores using both traps and venom to catch and immobilize the prey.  The trap is the web or orb.  In the case of the Golden-orb Spider it is made from a yellow silk which gives the spider its name.  Outside the forest the web is made from a deeper yellow silk which attracts bees so a large percentage of its diet in more open areas is bees.  Inside the forest it is made from a much paler silk.

Normally with orb weavers when something lands in the web they rush towards it and envelope it in sheets of silk to completely immobilize it before injecting the venom. The Golden-orb Spiders on the other hand bite first and then wrap in silk.  If the victim caught in the web is a large or aggressive ant or wasp she won’t take it on because there is a good chance she will be stung o bitten before she can get her bite in.

Webs are fascinating structures.  Although not so obvious to the human eye each spider has a web that is structurally pertinent to the species.  That means there are as many different types of webs as the number of species that create them.  As most people are aware the web is made from silken strands that are meticulously meshed together to produce one of nature’s most amazing death traps.

Silk is not exclusive to spiders, some other invertebrates are capable of producing silk, it is just that spiders are the unreserved masters in the production and utilization of silk and all spiders are capable of producing silk.  Silk itself is a remarkable substance.  It is a proteinaceous material stored as a liquid in the spinning glands.  When spun by the spider it turns from a water soluble liquid to an insoluble silken thread and this change occurs due to tension orienting the molecules rather than exposure to air.  The nature of the thread means it has both strength and elasticity. Spiders can produce many types of silk depending upon the use to which it will be put.  In a web there may be dry silk which is stiff and used as the framework while a moist viscous silk capable of stretching 300% of its original length is used as the sticky catch net.

Golden-orb Spider

Golden-orb Spider, (Nephila clavipes) producing silk

The spider has 3 pairs of independently mobile spinnerets on its abdomen.  Each spinneret ends in a spigot through which the silk gland exudes the silk.  As the proteinaceous silken thread is produced other cells in the silk glands secrete mucopolysaccharides which give it a viscous coating.  The mucous coating takes water from the atmosphere which separate into small droplets along the length of the fiber which in turn gives it the highly elastic quality to take the momentum from a large insect hitting the web as well as the glue-like adhesiveness which then holds it there.

Nephila clavipes spinnerets

Golden-orb Spider close up of spinnerets

I used extension tubes with a 105mm macro lens to try and capture a close up of the spinnerets of this Golden-orb Spider.  The spider is fairly large which made the task a little easier.  You can see the silken line being produced as well as the mucous globules along its length.

Philip Davison is a Biologist, Writer and Photographer Based in Costa Rica.

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6 responses to “Shining a Golden Light on Serpent Eyes

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  1. Fascinating stuff Philip, especially about the silk from the spiders. It never occurred to me that the silk was stored as a liquid. I love the close up shots.

    “Remember if you visit the area it is highly unlikely that you will see a snake…”

    It’s sure a lot easier to see one when the friendly neighborhood naturalist plunks one down in the middle of your breakfast table…good times!

  2. Thank you Philip ~ Julijana and I talk constantly (still!) about our December 2012 visit, which you summed up nicely with the phrase “Invariably these will be the people who will find [snakes].” After all our pre-occupation, we saw a juvenile snake the second I stepped 6″ off the path to answer the call of nature. I am thankful it was a scorpion who got me and not one of your bothrops friends. The bumpy ride out at high speeds did not sound like fun. Shoulder still twinges occasionally from falling off the waterfall (and people ask, “wait, this was a vacation, right?”), but we are still planning on returning. Your hikes were a watershed in my appreciation of our world. All the best, Larry and Julijana

  3. Apologies for “sort of” abusing your comment column. I wanted to ask if you have more photos available of the orchid bees: I am working on a book cover that they would work very well for, and “the more bees from different perspectives the better.” I will need to isolate them from the background, but need images of live bees working; and I love the photo of the dead bee with the orchid pollinate on his head. I’m willing to pay for images that I end up being able to use. I am hoping you might have more that are not posted here? (June 2011). Thank you for your assistance. You have created a wonderful scientific resource here. Thank you.

    Margaret Cotrofeld

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