"... he that breaks a thing to find out what it is

has left the path of wisdom."

    Gandalf the Gray to Saruman the White, in The Lord of the Rings: The Fellowship of the Ring

    John Ronald Reuel Tolkien (1892-1973)

Greater Hispaniolan tarantula, Phormictopus cancerides, female. Near Cabral, south-western Dominican Republic, Hispaniola.

PHYLUM ARTHROPODA: ARTHROPODS

    This is by far the largest taxonomic aggregation of animals, perhaps comprising more than three quarters of all extant organisms. Every single terrestrial and aquatic habitat on Earth has been colonized by arthropods of one kind or another.

    These organisms probably arose from a worm-like form, back in the early Cambrian Period. Their closest living relatives are the onychophorans, which were discussed in the previous section.

    The term "arthropod" derives from the Greek composite word meaning "that which has jointed legs" and, indeed, this is one of the main characteristics of the whole phylum. The locomotive appendages, as well as mouth parts, wings, antennae, and ovipositors of members of this group are jointed to the body, and are most often divided into movable sections themselves. This is a resulting need of their other trait: all arthropods possess a chitinous or calcareous exoskeleton that must be shed by a process of ecdysis (molting) as the animal grows. Since the exoskeleton is rigid, the appendages need to be jointed in order the be able to be moved.

    While being encased in a rigid armor would seem to be excessively confining from the point of view of softer bodied organisms with an internal skeleton (like us), indeed arthropods are immensely successful animals. Those that are aquatic breathe through gills, and often reproduce externally, by releasing eggs and sperm into open water. Terrestrial species breathe through tracheae that open to the exterior through tiny spiracles along their bodies. These forms reproduce internally, either with males passing their sperm to to females through spermatophores, as is the case with many arachnids and chilopods, of  by direct contact of their respective genitalia, as happens with most millipedes and insects.

    A number of groups within this phylum, notably some crustaceans, centipedes, and insects carefully and fiercely protect their eggs and young. This behavior, quite uncharacteristic among invertebrates in general, ensures that a greater number of offspring will reach reproductive age, in their own turn.

    Although arthropods are so different from us humans that we could almost seem to belong in different planets, and in spite of the fact that so many people look on them with scorn, revulsion, and fear, life on Earth as we now it today would be impossible without them. We feed on many of them (lobster, crabs, even some insects) and they feed on us (mosquitoes, horseflies, and ticks). They eat our crops (land crabs, locusts, and caterpillars) but they also pollinate our crops (butterflies, bees, and flies). They bite and sting us (centipedes, spiders, fire ants, and scorpions) but those same also hold back hordes of disease-carrying others (cockroaches, assassin bugs, and sand flies). They may have diets that are repulsive to us (maggots, dung beetles, and pillbugs) but it is their diets which keep our environment free of rotting corpses and pestilence. They destroy our furniture (termites and wood borers) but those same annually recycle billions of kilograms of dead wood, keeping forests healthy. They eat our clothes (cloth moth caterpillars) but also give us materials to clothe ourselves with (silk-moth caterpillars).

    In the end, the same bee that stings us will give us honey.

    And even aside from the direct and mediate, willing and unwilling relationships that we may sustain with them, arthropods are sublime creatures worth pondering, plain and simple. The industrious societies of ants and termites; the impossibly complex color patterns of many butterflies and moths; the hordes of land hermit crabs in their yearly pilgrimage down to sea to spawn; the delicate fastidiousness with which a tarantula grooms its fangs after its last meal; the agility of a centipede as it climbs up a branch; the blurring speed of a mantid shrimp pouncing on its next victim; the parsimonious undulations of a millipede's legs as it walks; the studied movements of a jumping spider looking for the easiest route to the next perch; the jewel-like iridescence of a hawk wasp; the mechanical walk of a scorpion; the helicopter-like hovering of a dragonfly; the symmetry of a dew-covered spider's web; the eerily human-like stare of a praying mantis as it swivels its head to look at you right in the eye...

    God made arthropods to make our life on this planet even possible.

Eight-Legged Wonders

CLASS ARACHNIDA: ARACHNIDS

    Most arachnids (spiders, opilionids, scorpions, sun spiders, whip scorpions, etc.) prey on the abundant insects with which they share West Indian grasslands, swamps, and forests. Named after the Greek weaver goddess Arachne, (in allusion to the webs of many spiders), some members of the class, however, are incapable of producing silk.

    Not all are predatory, either. A vast number of species of mites (a group that include ticks) are parasites of other animals or feed on dead organic matter. But the largest spiders, whip spiders, and scorpions can prey on small vertebrates. As a group, arachnids are the main terrestrial arthropod predators in the Antilles, although some mites are aquatic, being able to breathe through their thin bodily walls.

    Arachnids have two body sections, a cephalothorax and an abdomen, a trait they share with their distant relatives, horseshoe crabs and the extinct eurypterids. They have four pairs of legs, and also two pedipalps, one on each side of the mouth. Pedipalps are unspecialized and leg-like in most spiders and solfugids (albeit used as intromitent sexual organs by males of many species). Alternatively, they are modified into grasping pincers in scorpions and pseudoscorpions, or into what resemble sickles bristling with fierce spines used for grabbing prey in a deadly embrace, as in whip scorpions and whip spiders. Finally, instead of the complex mandibles of most miriapods, crustaceans, and insects, arachnids possess simpler structures called "chelicerae". These are appendages tipped with sharp fangs used to pierce and inject venom into the bodies of their prey. In fact, arachnids cannot eat solid food but, rather, enzymes found in their venom and saliva soften the insides of their victims. They then proceed to suck in the liquefied tissues of their prey. I such way, a spider will feed on its meal until only an empty husk of the latter is left behind. This is a thorough, if slow, process. A large tarantula, for example, will chew on a cockroach or even a mouse for hours, sucking in their liquefied flesh until only a tiny ball of indigestible chitin or hair remains.

    On the other hand, the chelicerae of parasitic arachnids are modified into piercing needles with which they feed on already liquid nourishment, as is the case with the blood-sucking ticks.

Order Acarina: Mites

    These are the most abundant and varied of all arachnids. However, most are tiny (less than one millimeter in length), and even microscopic. Ticks comprise an exception to this rule, since some can be relatively large. Ticks usually feed on the bodily fluids of vertebrates, though some are parasites of invertebrates. Several species are important vectors of diverse pathogens, like those that cause lime disease.

    Some velvet mites are also among the giants of their order, and are predators of small invertebrates in leaf litter or under rocks.

Many mites are parasites of vertebrates. Such are the ticks, (order Parasitiformes), and they do not only feed off dogs and cats.

This Sphaerodactylus roosevelti dwarf gecko has a tiny tick (species undetermined) attached behind its eye,

while an even tinier mite (a pterygosomatid, probably Geckobia sp.) is inside its ear.

Guanica State Forest, south-western Puerto Rico.

Ticks, possibly Amblyoma dissimile, on the neck of a greater Puerto Rican boa, Epicrates inornatus. Cambalache State Forest, northern Puerto Rico.

(Photograph courtesy of Mr. Alfredo Colon).

A tick (species undetermined) clings to a toad. Windsor, central Jamaica.

Red velvet mite, (order Acariformes), species undetermined. This comparatively huge species is often found under rocks in xeric areas.

Guanica State Forest, south-western Puerto Rico.

Order Opiliones: Opilionids

    Opilionids (the "daddy-longlegs" of English-speaking countries) are not true spiders, in spite of the strong resemblance between the two groups. Their bodies almost look like small spheres with none of that discernible partition between the cephalothorax and the abdomen that is so obvious in spiders. Predators of smaller invertebrates, they thrive in the humid microhabitats under rocks and debris.

    In spite of the small size of their bodies their legs are extremely long (hence their common name) and serve the function of antennae as well as locomotion.

Opilionids, species undetermined. Guilarte State Forest, west-central Puerto Rico.

Opilionid, Vonones sp. Carite State Forest, east-central Puerto Rico.

Opilionid, species undetermined. El Yunque National Forest, north-eastern Puerto Rico.

Mating pair of opilionids, species undetermined. El Yunque National Forest, north-eastern, Puerto Rico.

Opilionid, species undetermined. Guana Island, British Virgin Islands.

Order Scorpiones: Scorpions

    The approximately 1050 living species of scorpions belong to one of the most ancient terrestrial metazoan groups on Earth. As it is known today, their lineage dates back to the Silurian Period, 400 million of years ago, when some marine species ventured onto land and developed the capacity to breath gaseous oxygen. Several dozen species inhabit the Antilles. All scorpions have their pedipalps modified into pincers with which they seize and tear apart their prey.

    Scorpions are related to the largest arthropods known: eurypterids. These were fearsome predators - some reaching two meters in length - that actively hunted for their prey in the oceans of the Silurian and Ordovician periods. Even some extinct terrestrial scorpions might have measured about a meter in length, perhaps being the most massive land invertebrates that ever existed.

    All scorpions have the same basic bodily plan. To the frontal section, or prosoma, are attached all locomotive appendages, as well as the chelicerae and pedipalps. On the underside of the prosoma, a pair of specialized sensory organs, the feather-like pectens, serve to detect vibrations in their surroundings. Then follows the opisthosoma, itself divided into a mesosoma and a metasoma (this last is the scorpion's "tail"). The last segment of the metasoma is modified into a telson or stinger, containing two toxin-producing glands opening each into a duct through which the venom flows at will, as the animals attacks its prey or defends itself. The sting of West Indian species can be painful, but none are known to be fatal to humans.

Buthid scorpion, Centruroides guanensis, female. Santa Cruz del Norte, north-eastern Cuba.

(Photograph courtesy of Mr. David Ortiz Martinez).

Buthid scorpion, Centruroides barbudensis, female. Saline, Saint Bartholomew.

(Photograph courtesy of Mr. Karl Questel).

Buthid scorpion, Rhopalurus princeps, female. Enriquillo National Park, south-western Dominican Republic, Hispaniola.

Buthid scorpion, Rhopalurus garridoi, female. Guantanamo Naval Base, Guantanamo, south-eastern Cuba.

(Photograph courtesy of Mr. Joseph Burgess).

    Scorpions are rather unusual among invertebrates in exhibiting a rather elaborate degree of parental care for their offspring ("scorplings"). These last are given birth, instead of hatching from eggs, and the females will carry them on their back for some time until they are able to fend for themselves.

Order Solifuga: Sun Spiders

    These arachnids are more commonly found in desert areas. They are not venomous, but the larger species possess strong chelicerae capable of delivering a powerful pinch. Subjects of several ridiculous legends and superstitions, (including some among soldiers I spent time with in Iraq) these creatures are actually quite harmless.

Sun spider, Ammotrechella sp., female. Saline, Saint Bartholomew, Lesser Antilles.

(Photograph courtesy of Mr. Karl Questel).

Order Amblipygi: Whip Spiders

    There are two related orders of "whip scorpions". The "whips" of amblipigids are actually an elongated first pair of legs, held and used in the same fashion as an insect's antennae. Amblipigids - the tailless whipscorpions or (better named) "whip spiders", are denizens of the spaces under rocks, fallen logs, rock crevices, and caverns. Like most macroarachnids, they are predators of insects and small invertebrates, which they capture with their spiny pedipalps and envenomate with their short but sharp chelicerae. Amblipigids are harmless to humans, although the spiny pedipalps of the largest species can draw some blood from a careless human hand.

    As is the case with the true scorpions, these arachnids have segmented abdomens, but in their case this body section is wide and flattened. The females of many species carry their eggs attached to the underside of their abdomens, until they hatch into tiny replicas of the adults.

    Although their pedipalps festooned with spines give whip spiders a horrid appearance to many humans, they are elegant creatures in their movements, as they nimbly walk while touching everything within their reach with their thread-like front legs.

    The females of many species plaster their eggs to the underside of their abdomen and carry them about until the hatchlings are born.

Order Uropigi: Whip Scorpions

    Members of the similar order Uropigi have, additionally, a long and whip-like appendage on the tip of their segmented abdomens. These, the true whipscorpions, or vinegarones, eject a foul-smelling fluid when they feel threatened. In some species, this substance is composed partially of acetic acid, and has an odor like that of vinegar, hence their common name. Like amblipigids, they have their pedipalps modified as hunting weapons to grab and hold their prey.

Order Araneae: Spiders

    Spiders are the typical eight-legged creatures that most people think of when the word "arachnid" comes to mind. Like the amblipigids and uropigids, all spiders have a "waist" that separates the cephalothorax from their abdomen.

    Unlike most other arachnid orders, spiders do not have segmented abdomens. The only exception to that rule are the very primitive Old World mygalomorphs of the family Liphistiidae.

    Modern spiders are divided into two basic groups: Mygalomorphae and Araneomorphae. Mygalomorphs are the more primitive, though they still share with "typical" spiders (araneomorphs) the same basic body and appendage structure. However, they two groups can be immediately distinguished by looking closely at their chelicerae. In mygalomorphs, the fangs move and close in a vertical and front-to-back fashion. On the other hand, the fangs of typical spiders move and bite in a sideways fashion, "pinching" their prey as they feed or, in defense, their attackers.

    Many spiders in both suborders exhibit protective maternal behavior. They enclose their eggs in silken sacks and, once the neonates are born, they often stay close to the mother, which cares for them for some time.

Suborder Mygalomorphae: Tarantulas and Their Kin

    As far as size goes, the most impressive spiders are the Mygalomorphae, many of them commonly known as "tarantulas". In fact, the name is something of an historical misnomer, since it was originally applied to some large wolf spiders near the village of Taranto, in Italy, and which belong to the unrelated araneid family Lycosidae. Some mygalomorphs are actually very small, but the largest species of South America and Africa have leg-spans wider than an adult human's spread hand.

    Like typical spiders, mygalomorphs produce silk, yet they do not spin nets. Their silk is variously used to line their lairs, create egg-sacks, and in the case of trap-door spiders, to form a hinge for the earthen door to their burrows.

    There are several families in this suborder with West Indian members, like Theraphosidae, Barychelidae, Ctenizidae, and Dipluridae.

    Perhaps the largest family of the group is Theraphosidae. Most theraphosids are ground dwellers, and some are the largest living arachnids. Indeed, the most massive spiders are both South American: the Goliath tarantula, Theraphosa blondi, and its sister, Theraphosa apophysis.

    All tarantulas prey mainly on insects and other arthropods, and the largest will kill and devour small vertebrates like lizards and mice. In fact, some are called "bird-eating spiders", maybe for being occasionally found resting inside birds' nests after devouring the chicks.

    In spite of their menacing appearance, many tarantulas are actually docile creatures toward humans, and will never attack a person unless it is in self-defense. All the same a large, cornered tarantula raised on its hind legs and baring its long, shiny black fangs is a sobering sight for anyone intending to pick it up with bare hands. During the mating season, the males of some species are particularly ill-tempered and may indeed lunge to bite at the least provocation.

    Apart from their fangs and venom, some American tarantulas have a peculiar defense mechanism. Upon feeling threatened, they will vibrate their hind legs against their upper abdomens. Tiny barbed hairs ("setae") covering the abdomen will then fly through the air, finding their way to the mucous membranes of the mouth, nostrils, and eyes of the attacker. For many predators - and humans - the result is an obnoxious irritation that may last for hours.

    The males of many species are more mobile than the females, especially during mating season. Then, each of them may wander far and wide in search of a cantankerous - and often much larger - female that must be seduced by some sort of mating ritual, if he is not to find an ignominious end as her dinner, instead of her lover. Through stereotyped movements and touches, which vary by species, the male immobilizes his mate and then introduces into her genitals a pack of sperm (a "spermatophore") previously attached to the tips of his own pedipalps. During this operation, the male usually keeps the female's fangs at bay by holding them back with his front legs, which often have a sort of spurs for this purpose. If something does not go horribly wrong for him during the mating process, he then will make a hasty retreat and search for another prospective mate. Adult males that have mated several times will sometimes die soon after. Females, on the other hand, may live for many years.

A male greater Puerto Rican tarantula, Cyrtopholis portoricae, courts a female (inside the burrow) by tapping the entrance gently.

This individual is missing a leg, perhaps lost to a predator or rival.

Juncos, east-central Puerto Rico.

The tibial spurs of a male Cyrtopholis bartholomaei are used to keep at bay the long fangs of the female during amorous encounters.

Guana Island, British Virgin Islands.

    For most practical purposes, tarantulas are blind. Their tiny ocelli can only distinguish between light and darkness and since, at any rate, the organisms are nocturnal they find their way by the use of sensitive hairs on their legs and bodies. In fact, a tarantula usually senses your approach just by detecting the vibrations caused by your moving feet.

    Somewhat at odds with their fearsome appearance, tarantulas (like all spiders, really) are fastidiously clean animals. Especially after eating, they will spend long periods of time rubbing their legs together and over their bodies in order to clean off any remains of their prey and other debris. They daintily lick the tips of their pedipalps and legs to the same purpose.

    Mygalomorphs are widespread in the West Indies, though the group is strangely absent or very poorly represented in some insular banks, like Jamaica's and some of the Lesser Antilles.

FAMILY THERAPHOSIDAE: TYPICAL TARANTULAS

Subfamily Theraphosinae

    Most Caribbean tarantulas belong to the theraphosid subfamily Theraphosiinae. And perhaps the most widespread genus of that subfamily in the region is Cyrtopholis. It is found in all the Greater Antilles save Jamaica, and several of the Lesser Antilles. These are medium-sized terrestrial tarantulas that frequently inhabit burrows made by themselves. Males in search of females will often be found during the day simply lying under rocks and logs.

Subfamily Ischnocolinae

    The genus Holothele of the theraphosid subfamily Ischnocolinae contains small tarantulas with rather long, spindly legs. Lighting-fast when attacking their prey or fleeing danger, these spiders are found under debris like termitaria, rocks, and fallen tree trunk. They make rather flimsy silken nests in such places. In the Caribbean region, these tarantulas inhabit the Greater Antilles and some of the Lesser Antilles.

Subfamily Aviculariinae

    The members of another theraphosid subfamily, Aviculariinae, are adapted to a life on trees. They have velvety pads made of microscopic hooks under the distal portion of the legs and pedipalps which help them to walk nimbly on branches and leaves. (Many terrestrial theraphosids have similar structures, but in them they are much less developed). Aviculariines are represented in the West Indies by the genera Avicularia and Tapinauchenius. The first, a genus of small to medium-sized arboreal tarantulas, includes the South American A. versicolor, which is also found in several of the Lesser Antilles. Another species, A. laeta, is endemic to the Puerto Rican bank, and is the northernmost member of its genus.

Aviculariine tarantulas make silken nests in their arboreal hideouts. This is the nest of a male Puerto Rican pink-toed tarantula, Avicularia laeta.

Virgin Islands National Park, Saint John, United States Virgin Islands.

(Photograph courtesy of Dr. Luis O. Nieves).

Puerto Rican pink-toed tarantulas, Avicularia laeta, adult male and juvenile. Virgin Islands National Park, Saint John, United States Virgin Islands.

This arboreal species makes tubular silk nests in holes in tree-trunks or in crevices in large boulders and limestone cliffs.

However, Virgin Islands' individuals seem especially adept at making their nests in the central rosettes of some species of bromeliads.

I had to peel away the leaves of the plant in order to photograph these individuals.

 

The colors of neonates and small juveniles of Avicularia laeta are markedly differently from those of adults.

They were once thought to be a different species, called A. caesia.

Guana Island, British Virgin Islands.

 

    Tapinauchenius sancti-vicenti is endemic to the Lesser Antillean islands of Saint Vincent and Saint Lucia. It is a large, velvety-brown or -black species that makes flimsy nests in crevices of tree trunks and boughs.

Windward tree tarantula, Tapinauchenius sancti-vicenti, female. Grande Anse, north-eastern Saint Lucia, Lesser Antilles.
These large and elegant spiders seem to be covered in brown velvet.

FAMILY BARYCHELIDAE

    Tarantulas of the family Barychelidae are small and resemble the aforementioned Holothele. However, some of the Caribbean species, mostly belonging to the genus Trichopelma, possess definite climbing abilities, and during the day inhabit burrows excavated under bark on tree trunks, or among root tangles in cloud forests. These hideouts are lined with silk and their entrances may be additionally covered with debris held together with yet more silk. About half of the know species in the genus are Antillean.

Barychelid tarantula, Trichopelma sp. Dominican Republic, Hispaniola.

(Photograph courtesy of Dr. Rick C. West).

Barychelid tarantula, Trichopelma corozali. El Yunque National Forest, north-eastern Puerto Rico.

FAMILY CTENIZIDAE: TRAP-DOOR SPIDERS

    Some trap-door tarantulas of the family Ctenizidae are also found in the Antilles. Small in size, these species usually excavate their burrows under debris, and create a hinged door of soil held together with silk, and which seals the entrance when the animal hides inside.

Trap-door tarantula, genus Ummidia (undescribed species). Near Rabo de Gato, south-western Dominican Republic, Hispaniola.

Suborder Araneomorphae: Typical Spiders

    Many typical spiders are best known for their ability to spin webs which serve mainly as traps for their prey, usually insects (though some are able to entrap and kill even small bats and birds that fly into their webs). Some species, like those of the genus Nephila, produce silk which is stronger than a steel wire of the same width. As in mygalomorphs, the substance is produced from spinnerets located at the rear end of the abdomen. The ability to produce silk, and the precise uses given to it, vary greatly from one species to another.

    Many families of this suborder are found in the Antilles and many, like Araneidae, contains huge numbers of species.

    Although by far most araneomorph spiders are harmless to humans, the Antilles have their share of dangerously venomous forms. Several species of the genus Latrodectus (including the widespread black widow, L. mactans) are found in the region. Several species of Loxosceles (the genus that includes the equally infamous brown recluse) also inhabit some of these islands.

    A number of spiders, like those of the family Salticidae (jumping spiders), Thomisidae and Sparassidae (crab spiders), Selenopidae (huntsman spiders), and Lycosidae (wolf spiders) do not rely on web-spinning to capture their prey, but actively pursue their quarry, pouncing on them once the distance allows.

Puerto Rican giant crab spider, Olios portoricensis, female. (Family Sparasidae).

This individual was sitting on its eggs inside its silken nest, which I had to remove from its original location inside a bromeliad, and then open, in order to photograph it.

A threatened individual will defend itself readily with its large fangs. Indeed, the bite of this species can be quite dangerous.

Virgin Islands National Park, Saint John, United States Virgin Islands.

Giant crab spider, Olios sp., male feeding on a scarabeid beetle. Layou Valley, south-western Saint Vincent, Saint Vincent and the Grenadines, Lesser Antilles.

A crab spider, Misumenops bubulcus feeds on a flower fly, Pseudodorus clavatus.

Camp Santiago, Salinas, south-eastern Puerto Rico.

Huntsman spiders, Selenops lindborgi, (family Selenopidae).

First photograph: Guanica State Forest, south-western Puerto Rico.

Last two photographs: Humacao, east-central Puerto Rico.

Wolf spider (family Lycosidae) species undetermined. Near Cabral, south-western Dominican Republic, Hispaniola.

Fishing spider, (family Pisauridae), Dolomedes sp. Monte Iberia, Guantanamo, south-eastern Cuba.

(Photograph courte4sy of Mr. David Ortiz Martinez).

Fishing spider, probably Thaumasia marginella. San Juan Botanical Garden, San Juan, north-eastern Puerto Rico.

    Although social behavior is commonly known among some insects like ants, wasps, and termites, the same is rather uncommon among arachnids. However, some araneomorph spiders construct complex and seemingly chaotic webs which are the arachnid equivalent of a beehive. Many individuals, sometimes hundreds, inhabit the single structure, and cooperate in the capture and submission of their prey. These spiders are frequently very small, and when a large and powerful prey item say, a butterfly or grasshopper, falls into their trap they take turns biting and injecting venom into their victim. Given their tiny fangs, they do this in areas where the prey's chitin is thin, like the joints of the legs or neck. Sometimes after several hours and many such bites, the prey is finally immobilized, and all the spiders approach it safely to feed on its bodily fluids.

Collective web of social spiders, species undetermined.

The spiders themselves are tiny and hardly visible yet, collectively, still very efficient in killing prey far larger than they are.

Near Duverge, south-western Dominican Republic, Hispaniola.