Archive for the ‘Leaf-cutter Ant’ Tag



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), a migrant 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 as they did in the past.

Close up head of Golfo Dulce Anolis Lizard, (Anolis osae)

Golfo Dulce Anolis Lizard, (Anolis osae)

The wet conditions have allowed 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 frog 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 fiery 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.

Leaf-cutter Ant, media caste carrying leaf fragment

Leaf-cutter Ant (Atta cephalotes),, media caste carrying leaf fragment

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.

Army Ants, Echiton burchellii), carrying larva taken in a raid

Army Ants, (Echiton burchellii)

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.

Army Ants, (Eciton burchellii), swarm over the forest floor

Army Ants, (Eciton burchellii), on the move

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.

Army Ants, (Eciton burchellii), carrying dismembered spider leg

Army Ants, (Eciton burchellii), carrying dismembered spider leg

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

Army Ants, (Nomamyrmex sp), taking larvae from a Leaf-cutter Ant nest.

Army Ants, (Nomamyrmex sp), taking larvae from a Leaf-cutter Ant 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.  The 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.

Army Ants, (Nomamyrmex sp), taking larvae from a Leaf-cutter Ant nest.

A rare sight, Army Ants raid Leaf-cutter Ant nest

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.

Maxima caste of Leaf-cutter-Ant, (Atta cephalotes)

Leaf-cutter-Ant, (Atta cephalotes). Maxima caste


Setting the Forest Ablaze   Leave a comment

Felipe del Bosque Blog December 3rd 2012

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Always Take Your Umbrella

This week the precipitation reduced and the sun hours increased dramatically.   The rain has not stopped completely and some people were fooled by the beautiful summer-like conditions when the rain momentarily returned with a vengeance dumping 6 inches within 2 days.  But once the front passed over, the sun came back and it looks like we are into the dry season.

Hard to Spot

There were several new mammal sightings to record this week.  One night when I was out on a night tour with a couple of guests to the lodge a large caviomorph rodent, a Paca, (Agouti paca), walked across the lawns in front of us.  I initially spotted it due to the bright orange eye shine reflecting back within the beam of my flashlight.  Although I could see the eyes I could not make out the animal.  There are several commonly seen creatures in this area at night, the most frequently seen being the Common Opossums, (Didelphis marsupialis).  It continued moving towards us despite being caught in the beams of three flashlights.  As it approached more closely I could see that its coat was patterned ruling out an opossum but giving momentary optimism that it might be an Ocelot, (Leopardus pardalis).  I still couldn’t make out the body shape or whether it had a tail.  It disappeared into the vegetation surrounding the grey water filtering system.  I asked the two guests to remain where they were and I would go around the back to try and get a close look.  It turned round and headed back from whence it came so I came around the front again and we managed to finally illuminate it enough to get the identity.

Pacas are related to Agoutis, (Dasyprocta punctata).  The former are nocturnal and the latter diurnal.  The Pacas are fruit and seed eaters but will turn to more leafy material and roots if fruit becomes scarce.  They form monogamous pair bonds but quite often forage singly.  They are very secretive as in many parts of their range they are hunted for what is considered one of the best tasting meats you can eat.  Locally they are known as Tepezcuintle.

Driving Me Bats

The next morning I was with the same two guests on the Zapatero Trail.  As we walking towards a large hollow Milky Tree, (Brosimum utile), a very large bat took to the sky.  We had spooked it and it was now flying in circles above us, its dark body and outstretched wings silhouetted against the sky.  It briefly landed then took to the wing once more before returning a second time to fly up and disappear into the cavernous centre of the tree.  I did not have either the time or the diagnostic features with which to make an identification except for the striking size, a wingspan of well over 9 inches.  Costa Rica has a total of 111 species of bat, 80 of which reside on the Osa Peninsula.  In terms of size alone the options are limited but I simply didn’t obtain a good enough look to be able to say for sure what this one was.

Early Call

I caught my first sight of a Prothonotary Warbler, (Prothonotaria citrea), for the season.  Its stunning bright yellow plumage is so distinctive in amongst the background of leafy green vegetation.  The Summer Tanager, (Pingara rubra), remains the most vocal of the migrants around the grounds immediately adjacent to the main lodge area.  The Bright-rumped Atilla, (Atilla spadiceus), can now be heard calling just about every morning after an absence of some months.  If you do rise with the sun you will be greeted by a myriad of bird calls.  Some, such as the Chestnut-,mandibled Toucan, (Ramphastos swainsoni), don’t seem to stop, their calls can be heard throughout the day.


The change in the weather brings about changes in animal behavior.  It is getting more and more difficult to find amphibians at night but easier to find butterflies during the day.  I had some interesting sightings this week.  One butterfly that is not recorded as being on the Osa Peninsula most certainly is as I have seen it alive twice and dead once.  This week I found only a forewing but that constitutes further evidence that it does live here.

On several consecutive mornings I found in exactly the same spot on the Zapatero Trail a White-tailed Longtail, (Urbanus doryssus).  It is another of those butterflies that I have never seen before and unfortunately did not have my camera with me and so will probably never see again.

Leaf-cutter Ant

For the past month or so with it being damp but not soaking and sunny but not too dry the conditions have been perfect for the Leaf-cutter Ants, (Atta cephalotes) to be working assiduously day and night.  Now as the ground and air start to become a little drier the ants have started to change their foraging strategy.  They tend to limit their cutting and carrying of leaf to after sunset in the dry season.  The distance over which they have to carry the leaf means that it can dry out.  Any toxins the leaf contains, as it desiccates then they become more and more concentrated.  From here on in there will be less Leaf-cutter Ant activity during the day.

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.

 Photo Feature

 A Bright Splash of Color

Red is a very important color in the forest.  It is the complementary color to green and whereas green is a very cool color, red is a very hot color.  Birds have acute color vision and will see red a mile off in the forest.  Butterflies see at the red end of the spectrum as well as the ultraviolet end of the spectrum which is where most insect’s vision is concentrated.  Consequently the plants use red for their flowers to attract in pollinators.  Fruit when it ripens normally turns from green to red so attracting the fruit eaters which in turn act as seed dispersers.

Around the grounds of Bosque del Cabo at the minute are some very bright flashes of red on display is several flowering plants.  Out in the Tropical Garden there are several trees currently bearing fiery red blooms.  These are the African Tulip Trees, (Spathodea campanulata).  Its name gives away its origins but it is planted in parks and gardens throughout Costa Rica due to its tendency to flower year round providing 12 months of stunning color.  It is also known as the Flame of the Forest and one look would suggest why.

African Tulip Tree

Another distinctive and brightly colored flower can be seen growing directly from the trunk and branches of a several trees scattered around the lodge grounds, Rosa de Monte, (Brownea macrophylla).  Although not native to Costa Rica its distribution is closer being found in Panama.  The hemispherical orange flower is quite often used as a decoration on the tables at the Bosque restaurant.

Rosa de Monte

Just about everywhere you look around the Bosque gardens you will find Hibiscus, (Hibiscus rosa-sinensis).  The flowers are so distinctive that they could never be confused with anything else.  It is an easy to grow showy shrub and so will be seen in most areas of Costa Rica.  The petals can be anything from poppy red to pastel pink and appear on the plant year round.  A long protuberance issues from the centre of the flower.  At its tip are five fuzzy pincushion-like stylets.  Beneath this is a collar of finely stemmed yellow pollen bearing stamens.


Venture out of the gardens and into the forest this time of year you will find a tall red spike of a plant.  It is an endemic to the area, not found anywhere else, only on the Osa Peninsula, Aphelandra golfodulcensis.  Every day it produces 2 or 3 long tubular scimitar-shaped flowers.  It has a very specific pollinator, the hummingbirds with the long sickle-shaped bills of which there are two species commonly seen in this area, the Long-billed Hummingbird, (Phaethornis longirostris), and the Stripe-throated Hummingbird, (Phaethornis strigularis).  The hummingbirds hover in front of the flower, insert the bill which is a perfect match in terms of shape.  They take the nectar and at the same time the bill becomes coated in pollen which is transferred when they visit the next plant.

Aphelandra golfodulcensis

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 0.83 ins.  Total Weekly Rainfall 5.81 ins

Average Daily Rainfall 21.09 mm.  Total Weekly Rainfall 147.66 mm

Highest Daily Temp 85°F.  Lowest Daily Temp 74°F.

Highest Daily Temp 28.4°C.  Lowest Daily Temp 22.9°C.

Species List for the Week


  • Howler Monkey
  • Spider Monkey
  • White-faced Monkey
  • Kinkajou
  • White-nosed Coati
  • Agouti
  • Paca


  • Red-lored Amazon
  • Scarlet Macaw
  • Great Curassow
  • Crested Caracara
  • Double-toothed Kite
  • Black-hooded Antshrike
  • Chestnut-backed Antbird
  • Short-billed Pigeon
  • White-tipped Dove
  • Blue-crowned Motmot
  • Stripe-throated Hermit
  • Rufus-tailed Hummingbird
  • Blue-crowned Manakin
  • Red-capped Manakin
  • Chestnut-mandibled Toucan
  • Green Honeycreeper
  • Summer Tanager
  • White-shouldered Tanager
  • Bright-rumped Atilla
  • Dusky-capped Flycatcher
  • Great Kiskadee
  • Prothonotary Warbler
  • House Wren
  • Riverside Wren
  • Great Tinamou
  • Black-throated Trogon
  • Masked Tityra
  • Black Vulture
  • King Vulture
  • Turkey Vulture


  • Cat-eyed Snake
  • Central American Smooth Gecko
  • Clawless Gecko
  • Common Anolis
  • Four-lined Ameiva
  • Golfo Dulce Anolis
  • Litter Skink
  • Mediterranean House Gecko
  • Parrot Snake


  • Banana Frog
  • Black and Green Poison Arrow Frog
  • Fitzinger’s Rain Frog
  • Golfo Dulce Poison Arrow Frog
  • Marine Toad
  • Masked Smilisca
  • Red-eyed Green Tree Frog
  • Savage’s Thin-fingered Frog
  • Stejneger’s Rain Frog


  • Anartia Fatima
  • Antirrhea philoctetes
  • Dryas iulia
  • Drusilla glutophrissa
  • Heliconius erato
  • Heliconius ismenius
  • Heliconius sapho
  • Hermeuptychia hermes
  • Magneuptychia libye
  • Mechanitis polymnia
  • Morpho helenor
  • Morpho menelaus
  • Philaethria dido
  • Pierella luna
  • Taygetis andromeda


  • Alamandra  cathartica Flowering
  • Alpinia purpurata Flowering
  • Apeiba tibourbou Flowering and Fruiting
  • Arachis pintoi Flowering
  • Arundina graminifolia Flowering
  • Bauhinia variegata Flowering
  • Caryocar costaricensis Flowering
  • Cascabella thevetia Flowering and Fruiting
  • Citrus spp  Fruiting
  • Clusia rosea Flowering andFruiting
  • Clusia vallerii Flowering and Fruiting
  • Cocos nucifera Flowering andFruiting
  • Crestentia alata flowering and Fruiting
  • Costus speciosus Flowering
  • Couroupita guianensis Flowering
  • Dypsis lutescens Flowering and Fruiting
  • Etlingera elatior Flowering
  • Ficus insipida Fruiting
  • Heliconia chartacea Flowering
  • Heliconia latispatha Flowering
  • Heliconia pogonantha Flowering
  • Heliconia psittacorum Flowering
  • Heliconia rostrata Flowering
  • Hibiscus rosa-sinensis Flowering
  • Hymenaea coubaril Fruiting
  • Hymenocallis littoralis Flowering
  • Ixora coccinea Flowering
  • Lantana camara Flowering andFlowering
  • Lagerstroemia speciosa Fruiting
  • Morinda citrifolia Fruiting
  • Musa acuminate Flowering andFruiting
  • Nephelium lappaceum Fruiting
  • Piper auritum Flowering and Fruiting
  • Piper nigrum Fruiting
  • Piper umbellatum Flowering and Fruiting
  • Pleiostachya pruinosa Flowering
  • Plumeria rubra Flowering
  • Psychotria sp Fruiting
  • Stachytarpheta frantzii Flowering
  • Zammia sp Flowering



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