Monday 18th January 2016
Spiders are an amazingly diverse group of animals, the eighth most diverse group of animals of the planet in actual fact. It doesn’t take long while poking around in the undergrowth to come across a spider. Some build webs and some don’t but they can all spin silk, the orb weavers having the ability to spin upto seven different types of silk. The non-orb weavers tend to be ambush predators, remaining motionless in a strategic location where potential prey may wander innocently by unaware of the imminent life threatening danger. The ambush position could be on the side of a wall, atop a leaf or sitting on a flower head.
This Wandering Spider, (Cupiennius sp), was sitting perfectly still on a blank white wall at night. As many spiders are nocturnal predators the eyes play a lesser part in the identification and capture of a meal but that does not imply the spider is without the means by which to locate the exact location of its prey. The body, which at first sight looks smooth, upon closer examination can be seen to be covered in hairs of different lengths. These hairs form part of a battery of sensitive sense organs responsive to touch, vibration and moving eddies of air currents that allow the spider to detect a passing meal in the darkness.
The majority of hairs covering the body, which give most people the heebie-jeebies with regards to spiders, are tactile and touch sensitive, the stimulus of which will cause the spider to attack or run away. Between the shorter hairs, particularly on the legs are long fine hairs called trichobothria. These are super sensitive to the slightest movement in air currents which can be a giveaway for any larger creature passing by which could make a nice meal. The Wandering Spiders can even detect insects such as moths flying overhead which they jump and grab straight out of the air.
For those more stealthy prey items whose movements are too slow to disturb the air, they cannot avoid causing small vibrations of the substrate and the spiders are attuned to this also. Around the body but more particularly around the leg joints are slit sense organs which allow the spider to detect any vibrations moving through the substrate upon which it is placed.
Whereas the Wandering Spiders rely on their tactile senses at night during the day there are spiders that actively hunt down their prey visually. The Jumping Spiders prefer to hunt in full sun. The most obvious feature are the large anterior eyes with which they can locate and subsequently stalk their victims. They stealthily approach to the point where the potential meal is within striking distance. The spider braces itself and then pounce. The fangs are embedded upon impact, pumping venom into the victim which is held in a death grip by the front pair of legs.
Hunting the Hunters
The spiders may be highly adapted carnivores with specialized hunting techniques but they too in turn have predators specialized to catch and eat them. Not the least of these are the giant Helicopter Damselflies, (Megaloprepus caerulatus), the largest damselflies on the planet. They can be seen flying along the sunlit trails through the forest. The peculiar motion of the blue/black tipped wings gives the impression of rotating helicopter blades. What may at first seem like a somewhat erratic flight pattern actually has design. The more astute observer will notice that they have the ability to fly vertically up and down as well as horizontally in and out. But what are they seeking? The large eyes and acute vision are scanning spider webs in front of which they momentarily hover scanning for the silken structures builder. Once located the spider is grabbed in the legs of the damselfly which goes into reverse gear before biting off the spiders head and legs to finally gorge itself on the soft body parts.
The damselflies can be recognized when they alight by the habit of folding the wings together over the body. Their cousins, the dragonflies keep the wings held out to the sides when at rest. During the day it is not too often that they do rest. Each individual has a perch from which it frequently takes off to investigate any passing creature that might make a meal or another dragonfly that might prove to be a mate or another dragonfly that might be a rival for that meal or mate. They make aerial sorties swooping at speed, hovering in place and if unmoved to action return to the perch for a short while before they are off again on another sortie.
They differ from the more delicate damselflies not only by how they hold their wings but also in the structural placement of the eyes. Damselflies have two large compound eyes widely separated on either side of the head. Dragonflies have two large compound eyes that meet together for a greater or lesser part of their margins on top of the head. However no matter where the eyes are placed they allow for excellent diurnal vision which combined with the unsurpassed aerobatic proficiency make these some of the masterful airborne hunters.
As we move into the dry season the hot and parched conditions stimulate many of the plants into flowering. This is most certainly true of the orchids. There are two orchids that can be seen blooming at the moment in the area. One is a non native terrestrial orchid, the Bamboo Orchid and the other is a native epiphytic orchid.
The Bamboo Orchid is a native of South East Asia but is planted in many parts of Costa Rica as a beautiful ornamental edging plant. Bamboo refers to the long erect stalk that resembles that a of a bamboo grass. The attractive purple flowers appear throughout the year giving a nonstop display of color for the back of a flower border.
The majority of orchid species in Costa Rica are epiphytic, that is they grow on the outside of trees without harming them. Generally to see orchids you need to be at the top of the canopy, 88% of Costa Rica’s 1400 orchid species are to be found there. Many of the orchids flower from December into January but some may be seen flowering at any time of the year. This particular specimen was found growing close to the ground near the base of a large tree. Due to the diversity of genera and species the identification of orchids, like so many tropical plant and animal taxa, is the realm of specialists. For most visitors it is enough to see and enjoy the exotic blooms should you be lucky to encounter them.
Philip Davison is a biologist, writer and photographer based in Costa Rica.
Felipe del Bosque Blog November 18th 2013
This week started as the last week ended with lots of rain. Previously the rain had been falling at night but over the first few day of this week it started pouring day and night. Then a profound change occurred the sun came out and continued to return every morning to give us three days of beautiful dry conditions.
The transitional period between wet and dry season certainly make predictions difficult. Many aspects of plant and animal behavior rely on abiotic or environmental cues. Once we move into the dry season those changes will stimulate many of the plants to flower. Consequently there will be a lot of hummingbird, bat and insect activity around the nectar producing blooms. But as yet we are waiting for that change to occur.
Present and Correct
It has been quite a quiet week as far as mammal sightings are concerned. All the four species of monkey were spotted at many points around the grounds. Agoutis, (Dasyprocta punctata), can be seen on a daily basis near the Bosque restaurant. One was seen with a baby this week. Red-tailed Squirrels, (Sciurus granatensis), can be seen around the open areas of the lodge while Alfaro’s Pygmy Squirrel, (Microsciurus alfari), can be found without too much searching in the forest. These plain brown, sparse tailed, small chipmunk sized squirrels hop around at low levels of the forest and more often than not will cling head down on the side of a tree trunk and chatter ferociously at you.
Sing For Your Supper
The migrant birds, many of which are tanagers and warblers are still arriving. Summer Tanagers, (Piranga rubra), have set themselves territories in the gardens in front of the restaurant. Here they are joined by Cherrie’s Tanagers, (Ramphocelus costaricensus), males with their bright scarlet rumps being followed by harems of orange-brown females. Up in the branches of the trees are noisy flocks of Golden-hooded Tanagers, (Tangara larvata).
The army ant swarms continue their relentless marches through the forest at several locations on the property. They attract a lot of attendant bird life, many species of woodcreeper, trogons and of course the ever present Grey-headed Tanagers, (Eucometis penicillata).
Flying in the Face of Confusion
The migratory Green Urania, (Urania fulgens), moths are continuing to build in numbers. Butterfly numbers increase when the sun is shining but it will be several months before they hit their peak. Around the pond the dragonflies are starting to be seen more frequently, the bright blues and reds of these agile aerial hunters dart to and fro before settling momentarily of a leaf. Their heads turn this way and that, the acute vision with which they are gifted allows them to see predator, prey, mates and rivals, the presence of which causes the observer to react very quickly. Predators they avoid, prey they will catch, mates and rivals they will chase.
Within the darker confines of the forest flies an insect that both mesmerizes and inspires awe in those seeing it for the first time. Damselflies would be considered by most as being the smaller, more delicate relatives of the dragonflies. Here in the forests surrounding Bosque del Cabo flies the largest damselfly on the planet, the Helicopter Damselfly, (Megaloprepus caerulatus).
The first words used by guests upon returning from the forest where they have witnessed this spectacular creature for the first time are “I saw something flying like a helicopter”, or there were two large insects flying round each other.
The body is long and needle-shaped.with a broad tip. The wings are heavily veined and made of thin transparent tissue like clear cellophane. As the creature flies the wings catch the light and glint in the sun. But the confusing part about what is being seen is in no small part due to the bluey-black and silver-tips to the end of all four wings. When in flight they give the impression that the wings are moving in the same fashion as the rotor blades of a helicopter, hence the name.
The Helicopter Damselflies are spider-eating specialists. They have the ability to fly vertically up and down as well as horizontally in and out which you will see them do in front of a series of spider webs. When they find the silk spinner, they grab it in their legs, reverse backwards, nip of the head and legs then proceed to devour the softer body parts.
It is not uncommon to see the Helicopter Damselflies along the trails but it is not the easiest insect to photograph. When at rest they fold their wings back and over the body. This is your opportunity as it was mine. There is a smaller species, Mecisogaster ornata, which is also frequently seen and has yellow tips to the wings.
This week I decided to take a look at and photograph some of the plants that grow next to the roadside and are so often ignored. They are there every day and most flower continuously year round but everyone just walks by and doesn’t notice. But if you sink to your knees and go down to their level then you will see that they are just as pretty as the large showy blooms sported by many of the shrubs and trees..
One low growing herbaceous plant with deep green foliage offsetting its tiny yellow flowers is the Florecilla, (Baltimora recta). It belongs in the daisy family (Asteraceae). Another plant is the same family is the Dandelion, (Emilia fosbergii). It is not a plant native to the Americas, its origins belong in the Old World, but now its delicate pink and purple flowers can be seen decorating any sunny roadside throughout the country.
There are several sprawling ground huggers to be found everywhere on the Bosque verges. One has small yellow cup shaped flowers, Escobilla, (Sida rhombifolia). This plant is found all over the planet in tropical and subtropical open areas. Being so common you would think it would be familiar to a lot of people but probably only the discerning botanist would notice it. In many situations growing beside the Escobilla is a plant with small pink pom-poms as flowers. It is not the flowers that normally catch the attention with this plant but rather the leaves. When touched, the leaves instantly fold up and the stem droops. The reason for this is not entirely understood but there are several theories. It could be to escaped grazers but I can’t see why a folded leaf would not be consumed over an open leaf. When it rains the pounding of the droplets may damage the leaf so again it folds. Finally at night the leaves close. This may aid in reducing transpiration but once more in the evening when the temperature drops, the relative humidity of the air increases so I am not sure about that one either. Nonetheless it certainly remains a feature that in particular fascinates children.
Philip is a biologist, writer and photographer at Bosque del Cabo Rainforest lodge on the Osa Peninsula, Costa Rica.
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 2.61 ins
Average Daily Rainfall 9.50 mm. Total Weekly Rainfall 66.3 mm
Highest Daily Temp 89°F. Lowest Daily Temp 74°F.
Highest Daily Temp 32.2°C. Lowest Daily Temp 23.7°C.
Species List for the Week
- Central American Squirrel Monkey
- Mantled Howler Monkey
- Spider Monkey
- White-faced Capuchin Monkey
- Common Tent-making Bat
- Central American Woolly Opossum
- Red-tailed Squirrel
- White-nosed Coati
- Collared Peccary
- Red-lored Amazon
- Scarlet Macaw
- Great Curassow
- Black Hawk
- Black-hooded Antshrike
- Chestnut-back Antbird
- Common Paureque
- Lineated Woodpecker
- Pale-Billed Woodpecker
- Blue-crowned Motmot
- Short-billed Pigeon
- Long-billed Hermit
- Purple-crowned Fairy
- Stripe-throated Hermit
- Red-capped Manakin
- Streak-headed Woodcreeper
- Wedge-billed Woodcreeper
- Fiery-billed Aracari
- Chestnut-mandibled Toucan
- Summer Tanager
- White-shouldered Tanager
- Bright-rumped Atilla
- Dusky-capped Flycatcher
- Golden-crowned Spadebill
- Great Kiskadee
- Great Tinamou
- Black-throated Trogon
- Black Vulture
- Turkey Vulture
- Cat-eyed Snake
- Central American Smooth Gecko
- Clawless Gecko
- Common Anolis
- Four-lined Ameiva
- Golfo Dulce Anolis
- Mediterranean House Gecko
- Banana Frog
- Black and Green Poison Arrow Frog
- Fitzinger’s Rain Frog
- Masked Smilisca
- Marine Toad
- Red-eyed Green Tree Frog
- Savage’s Thin-fingered Frog
- Stejneger’s Dirt Frog
- Tink Frog
- Anartia fatima
- Anartia jatrophae
- Cithaeria pireta
- Dione juno
- Dryas iulia
- Eueides aliphera
- Eueides lybia
- Glutophrissa drusilla
- Heliconius erato
- Heliconius ismenius
- Heliconius sapho
- Heraclides cresphontes
- Junonia evarete
- Morpho helenor
- Morpho menelaus
- Parides erithalion
- Perophthalma lassus
- Pierella luna
- Pyrgus oileus
- Pyrisitia nise
- Saliana esperi
- Urbanus simplicius
- Acmella oppositifolia Flowering
- Allamandra cathartica Flowering
- Alpinia purpurata Flowering
- Anthurium salvinii Flowering
- Apeiba tibourbou Flowering and Fruiting
- Aphelandra golfodulcensis Flowering
- Arachis pintoi Flowering
- Arundina graminifolia Flowering
- Attalea rostrata Fruiting
- Baltimora recta Flowering
- Bauhinia variegata Flowering
- Brunfelsia grandiflora Flowering
- Calathea marantifolia Flowering
- Cananga odorata Flowering
- Canna sp Flowering
- Cascabella thevetia Flowering and Fruiting
- Castilla tunu Flowering
- Chrysobalanus icaco Fruiting
- Citrus spp Flowering and Fruiting
- Clusia rosea Flowering and Fruiting
- Clusia valerii Flowering
- Cocos nucifera Flowering and Fruiting
- Costus speciosus Flowering
- Couroupita guianensis Fruiting
- Cresentia alata Flowering and Fruiting
- Crotalaria retusa Flowering
- Cyclanthus bipartitus Flowering
- Emilia fosbergii Flowering
- Etlingera elatior Flowering
- Guaterria amplifolia Fruiting
- Hedychium coronarium Flowering
- Heisteria accuminata Fruiting
- Heliconia chartacea Flowering
- Heliconius clinophylla Flowering and Fruiting
- Heliconia latispatha Flowering
- Heliconia longiflora Flowering
- Heliconia pogonantha Flowering
- Heliconia psittacorum Flowering
- Heliconia rostrata Flowering
- Hibiscus rosa-sinensis Flowering
- Hymenaea coubaril Fruiting
- Ixora coccinea Flowering
- Lantana camara Flowering and Flowering
- Mimosa pudica Flowering
- Morinda citrifolia Flowering and Fruiting
- Musa acuminata Flowering and Fruiting
- Pandanus sp Fruiting
- Piper hispidum Flowering and Fruiting
- Pleiostachya pruinosa Flowering
- Plumeria rubra Flowering
- Psychotria solitudinum Fruiting
- Sida rhombifolia Flowering
- Spathodea campanulata Flowering
- Spondias mombin Flowering
- Stachytarpheta sp Flowering
- Thunbergia erecta Flowering
- Thunbergia fragrans Flowering
- Tocoyena pittieri Fruiting
- Virola sebifera Fruiting
- Zingiber spectabile Flowering