Archive for the ‘Eciton burchelii’ Tag

ARMY ANTS:  A LIVING WAVE OF BLACK DEATH   6 comments


Veridion Adventures. Philip Davison. Rainforest animals. Rainforest plants

November is upon us.  The wet season continues, relentless heavy rain falling if not all day then at least part thereof.  One day last week over 14 inches of rain fall in an overnight deluge.  The following day the forest trails were more akin to newly formed streams, the water flowing downhill until it reached a point where it could tumble into the main creek that runs through the grounds, swelling its volume and increasing its velocity to that of a raging torrent.   There have been some dry, sunny days and if the weather continues its normal pattern then progressively as we move through the month the number of rainless days should increase.

I have been away for a month and upon my return, as with each and every year, the first thing I hear is the call of the Summer Tanager, (Piranga rubra), which has spent the summer in North America.  Not much has changed in the area while I was away.   The resident wildlife can still be found without any effort.  The White-nosed Coati, (Nasua narica), populations are growing at a steady and sustained rate.  I have never seen as many wandering the grounds as I do now.  The solitary males are normally bold creatures, but the females tend to be shy and retiring.  Now, however, the females and their young will allow you to approach very close without scurrying off into the shelter of the trees.

Rainforest lizards. Costa Rica. Polychrotidae. Anolis osae. Osa Anole. Philip Davison. Veridion Adventures.

Osa Anolis, (Anolis osae)

The wet conditions have proved to be conducive in allowing the amphibians to continue their courtship and breeding.  There are not so many egg masses present as in the main breeding period, (May – July), but there are still several species spawning on a nightly basis.  Feeding on the eggs are the Cat-eyed Snakes, (Leptodeira septentrionalis), which can be found every night by the pond.  The ever-present anoles of several species can be seen in the forest.  The commonest and most obvious is the Osa Anole, (Anolis osae), with its bright orange dewlap.  If one male is signaling to another to leave his territory then you can’t miss that flash of color against the dark background.

Ants Are Everywhere

Ants are ubiquitous insects in the forest.  On the trees you will see lines of Tiger Ants, (Camponotus sericeiventris), walking in line, foraging for food.  They receive their name from the black and yellow coloration rather than an aggressive nature.  In the lawns you would be well advised to avoid stepping in those small powdering mounds of earth that betray the presence of Fire Ants, (Solonopsis sp), living just beneath the surface.  I have never known anything so small cause so much pain as the fire ants.  The problem is that they are so small you don’t know you are covered in them until they start to bite and they all do so together.  It would be almost impossible to miss the presence of Leaf-cutter Ants, (Atta cephalotes), in these forests, whether it be descending the tree trunks with freshly cut leaf fragments or seeing lines of ants moving as a green river, snaking across the forest floor as they make their way back to, the nests with, what essentially is composting material for their fungus gardens.  Leaf-cutter Ant nests occur every 100 meters or so in whatever direction throughout the forest and can easily be identified by the large waste tips of excavated material marking the nests’ peripheral boundaries.

Rainforest insects. Hymenoptera. Formicidae. Atta cephalotes. Leaf-cutter Ant. Philip Davison. Veridion Adventures.

Pebble-capped towers formed by heavy rain on Leaf-cutter Ant nest waste tip

Army Ants:  A Living Wave of Black Death

It is a warm day, the rain has stopped, the sun is shining and you are quietly walking through the forest, binoculars strung around your neck and camera in hand.  The air is still and there is little sound bar the occasional call of a bird here and there and the soft white noise of calling insects which is not too intrusive.  You walk in a state of reverie, not thinking about anything in particular, your eyes scanning the vegetation for small subjects to photograph or watching for movement that may indicate a bird or mammal is moving across your path.  It is a day for enjoying your surroundings and contemplating the life contained within.  You are blissfully unaware of the carnage being carried out in the forest ahead.

As you make your way forward you start to hear more birds calling.  Some of the sounds you are familiar with; a Black-hooded Antshrike, (Thamnophilus bridgesi), Bicolored Antbirds, (Gymnophythis leucaspis), and Chestnut-backed Antbirds, (Myrmeciza exul).  This seems as if it might provide some good photographic opportunities so you make sure the camera is ready with the correct settings.  Now some other birds fly past you and land on the tree trunks, most of them a variety of treecreepers; Streak-headed, (Lepidocolaptes souleyetii), Tawny-winged, (Dendrocincla anabatina), and Ruddy, (Dendrocinclo homochroa).  The bird calls are increasing in intensity, excitement and volume as you make your way to where they seem to be congregating.  As you approach you can see them briefy dropping from the vegetation to the ground and back up again.  There is another sound, a hum which pervades the air.  Having left your dreamlike state and become more acutely aware you see that you are surrounded by flies buzzing everywhere. You see one or two Gray-headed Tanagers, (Eucomectis penicillata), amongst the mixed bird flock, the presence of which along with the flies provide the clues as to what is happening.   Finally you hear, a sound like softly falling rain and yet there is not a cloud in the sky.  From about 5 meters in front of you and advancing rapidly towards you like a sheet of black polythene being pulled across the forest floor is a foraging front of Army Ants, (Echiton burchellii); a living wave of black death.

Rainforest ants. Hymenoptera. Formicidae. Dorylinae. Eciton burchellii. Army Ant. Costa Rica. Philip Davison. Veridion Adventures.

Army Ant, (Eciton burchellii), on the march

The feet of thousands of miniature assassins moving as one across the dried leaves give the illusion of rain falling.  You stand dumbstruck by the scene playing out in front of you.  As the procession of annihilation moves closer you can see down by your feet beetles, cockroaches and crickets running for their lives.  These are the lucky few.  The killers are insatiable.  Any small creature unfortunate enough to caught in their unrelenting path will be overwhelmed, stung to death, and then decapitated, dismembered and disemboweled.  The wickedly sharp mandibles of the army ant hunters slash and cut through exoskeleton, muscle and connective tissue.  The victim’s mutilated body fragments are then carried away by the mindless insect ghouls to provide a feast macabre for the larvae.  As fascinating to witness as this bloodbath at the macro level is, you had better move.  The ants are now crossing the path all around your feet. You might be too big for them to tackle, but the long stinger and virulent toxin can cause a lot of pain.

Rainforest insects. Hymenoptera. Formicidae. Dorylinae. Eciton burchellii. Army Ant. Costa Rica. Philip Davison. Veridion Adventures.

Army Ants, (Eciton burchellii), carrying severed spider leg back to feed larvae

For those insects capable of flight and able to escape the ravaging mandibles of the ants, the danger is not over.  The birds were attracted to the ant swarm to take advantage of the free meal they provide by flushing insects from their hiding places.  Gray-headed Tanagers are obligative followers of the army ants.  Wherever they are, you will find the tanagers.  The flies are there for the same reason.  These are Coffin Flies, (Phoridae sp).  When an insect attempts to escape by taking flight, the parasitic phorid fly swoops in, lays an egg and flies out again.  The eggs will hatch and the grub will eat the victim.

Army Ants are one of the major predators in the forest.  They rank alongside Boa Constrictors, Harpy Eagles and Jaguars as one of the top of the food pyramid predators in the forest.  They are a nomadic ant and they have to be nomadic because being such a super-efficient predator, should they settle in any one area for any length of time, they would deplete it of all small forms of life very quickly.

They have 2 three week cycles; a nomadic stage when they move in a flowing column of ants, the queen travelling with them, until they find a new hunting ground.  They do not construct a nest, they make a bivouac, generally at the base of a tree, which is a huge ball of ants held together by the interlinking of legs. The queen moves to center and swells up.  She starts to lay approx. 60, 000 eggs per day.  When the eggs hatch and the larvae emerge, the emit a pheromone which elicits a hunting response from the other workers.  They then move through the forest in a front anything up to 60 feet, (20 meters), across and take all small forms of life in their path: insects, small frogs, small lizards, small snakes, fledgling birds, if it is there then they will have it.  Once it has been butchered into small pieces, these are taken back via feeder columns to the bivouac to feed the larvae.  When the larvae pupate, the hunting response is switched off and  they return to the nomadic stage making their way through the forest once again.

A New Assassin

Rainforest ants. Hymenoptera. Formicidae. Dorylinae. Nomamyrmex sp. Army Ant. Costa Rica. Philip Davison. Veridion Adventures

Army Ant, (Nomamyrmex sp) carrying pupa from Leaf-cutter Ant, (Atta cephalotes), nest

There are many species of Army Ant and the species described above is the most commonly found in the area Echiton burchellii.  Last week I found a species that I had never seen before.  As well as slaughtering prey items on the forest floor, army ants will also enter the nests of other ants and take out the eggs, larvae, pupae, workers and queen.  They one ant they fight shy of taking on are the Leaf-cutter Ants.  There may be several hundred thousand in an army ant colony, there can be up to 8 million in a leaf-cutter ant colony.  The soldier leaf-cutters are huge and equipped with razor sharp mandibles.  They are programmed to fight to the death.  The army ants would lose so many of their own numbers if they were to raid a leaf-cutter ant nest.  Even if they come across them on a trail they will not interfere with them.

Rainforest animals. Hymenoptera. Formicidae. Atta cephalotes. Leaf-cutter Ant. Philip Davison. Veridion Adventures.

Leaf-cutter Ant, (Atta cephalotes), soldier

It was to my surprise therefore when last week a watched for the first time an army ant raid on a leaf-cutter ant nest.  Luckily I had the camera in my hand and found a place to lie down and take photos.  On this occasion the leaf-cutters seemed to be helpless to stop the nest being ransacked.  When I downloaded the images and looked at the images I did not recognize the species at all.  Despite their distinctive flat, square heads, extensive searching produced no I.D.  Eventually I found one photo and some information.  The genus is Nomamyrmex and it contains two species.  I am not sure which one I had been watching but I was happy to have witnessed an event I had never seen before being carried out by an ant I had never seen before and had the photos to prove it.

Rainforest insects. Hymenoptera. Formicidae. Dorylinae. Nomamyrmex sp. Army Ant. Philip Davison. Veridion Adventures.

Army Ants, (Nomamyrmex sp), raiding Leaf-cutter Ant, (Atta cephalotes), nest

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

 

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Small Balls of Fire   Leave a comment


Felipe del Bosque Blog June 4th  2012

Flash & Crash

The week started bright and sunny but after a few days the heat built up, the hot moist air rose, condensed in the upper atmosphere and those thunderstorms so typical at this time of year arrived.  Here the storms pass overhead more often than not, bringing with them spectacular lightning shows, thunder that rattles all the buildings down to the foundations and of course the inevitable torrential rain.

The bosque creek still is running very low, but it won’t take too many of these downpours to fill it up.  The ground, which for the time being is soft and sticky, will soon become wet and cloying.

Dripping New Life

Now that it has been wet for a month or so, conditions that have encouraged the male amphibians to be out calling, the females having joined them and we are starting to see lots of eggs.  The Red-eyed Green Tree Frogs, (Agalychnis callidryas), have been laying their eggs in small masses under the leaves overhanging the pond.  The Smokey Jungle Frogs, (Leptodactylus savegei), are foam nesters and their distinctive egg containing frothy masses can be seen around the pond.  The smaller Banana Frogs, (Dendropsophus ebrecattus), lay their eggs on the vegetation floating on the pond surface.

All 3 of the above species have initially taken their eggs out of the water to develop away from aquatic predators.  With each, the eggs develop until about a week, then the larvae will drop into the water where they have to undergo a tadpole stage before metamorphosing into a terrestrial or arboreal frog.

The Leaf-cutter Ants have now been stimulated into 24 hour action on all of the trails.  During the dry season they normally work at night, away from the drying effects of the sun and high temperatures that could possibly desiccate the piece of leaf they are carrying over such long distances thereby rendering all that hard work to useless.  Now, with a change in the humidity it is possible to cut and carry all day and all night.

Stop and You’re Dead

Over the past week it has not just been the Leaf-cutter Ants making their presence obvious; the Army Ants have been out in force too.  Their unmistakable foraging columns can be seen traversing the forest floor, a living river of ants moving with unswerving purpose.

If you are lucky you may see the foraging front that the columns are serving.  This is a relentless forward marching line of ants up to 60 feet across and 10 feet or so in depth.  It is the phase in the recurring cycle of Army Ant activity where they move through the forest killing, dismembering and transporting any unfortunate small creature too slow to escape their advancing numbers.

You will be alerted to the presence of the murderous hymenopterans by the excited activity of so many birds; Antbirds, Antpittas, Ant Wrens, Ant Shrikes, Ant-tanagers, Ant Thrushes, Ant Vireos, woodpeckers, woodcreepers, tinamous and the ever present followers of the Army Ants, the Grey-headed Tanagers.  These birds are here, not to feed on the ants, but to take advantage of the easy meal afforded them by the frantic efforts of the insects to escape the jaws of the ravenous hordes.

There will be a hum in the air near the front of the seething black mass of ants; this is the sound of parasitic Phorid flies that are in the vicinity for the same reason as the birds.  As insects are flushed from their hiding spots, in go the flies, lay an egg on them and then retreat post haste.

The ants return with the mutilated remains of recently dead prey to a bivouac, a massive ball of ants that provide temporary accommodation for the colony by linking together their legs to construct a nest of living bodies.  This shelters the queen and the larvae while they feed and grow.  As soon as they pupate, the bivouac deconstructs and the ants then enter their nomadic phase, moving through the forest until they arrive at new killing fields to start the carnage once again.

All mammal life is as normal with many daily sightings of Howler, Spider, Capuchin and Squirrel Monkeys.  Solitary male White-nosed Coatis can commonly be seen around the grounds of the lodge while out in the forest, large groups of females in attendance of their large litters of offspring have been seen, particularly on the Titi Trail.  Agoutis too have been seen walking around with young ones, which have now left the shelter of the dens, in close proximity.

Philip is a biologist, writer and photographer as well as the onsite naturalist guide at Bosque del Cabo Rainforest lodge on the Osa Peninsula, Costa Rica.

www.bosquedelcabo.com

 Photo Feature

 Ball of Fire

Paper Wasp Nest         Paper Wasp Nest         Paper Wasp Nest

I you look under the leaves of many of the plants around the grounds you will see suspended structures that vary in shape from globular to cylindrical with various forms in between.  These are the nests of the paper wasps.

Paper Wasp Nest

The shape of the nest tends to be unique to the species of wasp making it.  The nests are made from carton which is chewed up plant material, normally wood.  Sometimes the wasps can be seen around the bar and restaurant area scraping away the surface layer of wooden rails with their mandibles.  They chew it into a pulp from which they make the paper that gives them their names.  They pulp is deposited layer upon layer to build the nest which houses the combs that constitute the brood chambers for the eggs and subsequently the developing larvae.  The nest may vary in color depending upon the source of the original construction material.  Some nests may be adorned with decorative features such as hanging flanges.

Polybia sp         Polybia sp         Polybia sp

Wasps are carnivores and feed on a wide variety of small arthropod prey.  The paper wasps generally belong to the genus Polybia.  Depending upon species they range in size from about 1.5 inches to .25 of an inch.  They are generally dark in color but banded with yellow.  They don’t use the sting to kill prey, which they do with the mandibles.  The sting is used for defensive purposes and to that effect contains chemical agents guaranteed to cause maximum pain.  They may be small but they are pugnacious and will defend the nest with vigor.   To that effect it is probably better to view them from a distance rather than close up.

Polybia sp

Text and Photographs are taken from the forthcoming book:

The Natural History of Bosque del Cabo by Philip Davison

Temperature and Rainfall

Average Daily Rainfall 0.37 ins.  Total Weekly Rainfall 2.59 ins

Average Daily Rainfall 9.4 mm.  Total Weekly Rainfall 65.8 mm

Highest Daily Temp 90°F.  Lowest Daily Temp 75°F.

Highest Daily Temp 32.2°C.  Lowest Daily Temp 24.2°C.

 

Species List for the Week

Mammals

  • Howler Monkey
  • Spider Monkey
  • White-faced Monkey
  • White-nosed Coati
  • Common Opossum
  • Agouti
  • Red-tailed Squirrel

 

Birds

 

  • Orange-cheeked Parakeets
  • Scarlet Macaws
  • Red-lored Amazons
  • Crested Caracara
  • Pale-billed Woodpecker
  • Grey-necked Woodrail
  • Lineated Woodpecker
  • Chestnut-backed Antbird
  • Black-hooded Antshrike
  • Common Paureque
  • Short-billed Pigeon
  • White-tipped Dove
  • Long-billed Hermit
  • Rufus-tailed Hummingbird
  • Blue-crowned Manakin
  • Red-capped Manakin
  • Chestnut-mandibled Toucan
  • Blue-crowned Motmot
  • Long-tailed Woodcreeper
  • Banaquit
  • Cherrie’s Tanager
  • Golden-hooded Tanager
  • Green Honeycreeper
  • Red-legged Honeycreeper
  • Bright-rumped Atilla
  • Golden-crowned Spadebill
  • Great Kiskadee
  • Great Tinamou
  • House Wren
  • Black-throated Trogon
  • Masked Tityra
  • Black Vulture
  • Turkey Vulture

 

Reptiles

 

  • Central American Whiptail
  • Central American Smooth Gecko
  • Clawless Gecko
  • Common Basilisk
  • Five-lined Ameiva
  • Golfo Dulce Anolis
  • Mediterranean House Gecko
  • Norops limifrons
  • Northern Cat-eyed Snake
  • Salmon-bellied Racer
  • Tropical Bird-eating Snake

 

Amphibians

 

  • Banana Frog
  • Black and Green Poison Arrow Frog
  • Gladiator Frog
  • Golfo Dulce Poison Arrow Frog
  • Marine Toad
  • Red-eyed Green Tree Frog
  • Smokey Jungle Frog

 

Butterflies

 

  • Anartia Fatima
  • Arawacus lincoides
  • Archaeoprepona demophon
  • Ascia monuste
  • Autochton neis
  • Battus belus
  • Caligo eurilochus
  • Cupido comyntas
  • Eueides lybia
  • Eurema albula
  • Glutophrissa Drusilla
  • Heliconius cydno
  • Heliconius erato
  • Heliconius hecale
  • Heliconius ismenius
  • Heliconius sapho
  • Heraclides cresphontes
  • Hermeuptychia hermes
  • Marpesia berania
  • Mechanitis polymnia
  • Morpho helenor
  • Morpho Menelaus
  • Pareuptychia occirhoe
  • Perophthalma lassus
  • Philaetria dido
  • Phoebis sennae
  • Siproeta stelenes
  • Taygetis andromeda
  • Turesis basta
  • Urbanus simplicius
  • Urbanus tanna

 

Plants

 

  • Alamandra  cathartica Flowering
  • Alpinia purpurata Flowering
  • Anthurium salvinii Flowering
  • Apeiba tibourbou Flowering and Fruiting
  • Arachis pintoi Flowering
  • Aristolochia Fruiting
  • Arundina graminifolia Flowering
  • Astrocaryum standelyarum Fruiting
  • Atrocarpus heterophyllus Fruiting
  • Averrhoa carambola Fruiting
  • Brassavola nodosa Flowering
  • Brownea macrophylla Flowering
  • Calathea lutea Flowering
  • Callistemon viminalis Flowering
  • Cascabella thevetia Flowering
  • Chamaedorea costaricana Fruiting
  • Cocos nucifera Fruiting
  • Crestentia alata flowering and Fruiting
  • Clusia rosea Fruiting
  • Clusia valerii Fruiting
  • Costus speciosus Flowering
  • Couroupita guianensis Flowering and Fruiting
  • Eichhornia crassipes Flowering
  • Ficus insipida Fruiting
  • Garcinia madruno Fruiting
  • Genipa Americana Flowering
  • Gustavia brachycarpa Flowering
  • Hedychium coronarium Flowering
  • Heliconia chartacea Flowering
  • Heliconia latispatha Flowering
  • Heliconia pogonantha Flowering
  • Heliconia psittacorum Flowering
  • Heliconia rostrata Flowering
  • Hibiscus rosa-sinensis Flowering
  • Hymenaea coubaril Fruiting
  • Lacmellea panamensis Fruiting
  • Lantana camara Flowering
  • Lagerstroemia speciosa Flowering
  • Mangifera indica Fruiting
  • Miconia argentia Flowering
  • Morinda citrifolia Fruiting
  • Musa acuminate Fruiting
  • Naucleopsis ulei Fruiting
  • Pandanus tectonus Fruiting
  • Passiflora vitifolia Fruiting
  • Piper auritum Flowering and Fruiting
  • Piper umbellatum Flowering and Fruiting
  • Plumeria rubra Flowering
  • Psidium guajava Fruiting
  • Spathiphylum freidrichsthalii Flowering
  • Symphonia globulifera Fruiting
  • Terminalia catappa Flowering
  • Virola guatemalensis Fruiting
  • Virola koschnyi Fruiting
  • Vochysia ferruginea Fruiting

 

 

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