Amazing Arachnids: Whip Spiders

Adapted from pages 88-90 of Amazing Arachnids:

Imagine a world of giant horsetail trees, ferns, and clubmosses. Everything looks oddly familiar, but dramatically out of scale. Plants that you think of as being only a few inches in height are now tall trees. Huge dragonflies with 2-foot (0.6 m) wingspans hunt in the air, while 4-inch-long (10 cm) cockroaches and 2-foot-long (0.6 m) millipedes feed on the abundant decaying plant material on the forest floor. Small reptiles forage among the vegetation, and occasionally one is drowned in the water-filled stump of a clubmoss tree. Lurking in the swampy pools are large, salamander-like amphibians. This is the world of the Carboniferous Period 300 million years ago, and in this world another predator lived. This flat, spiderlike creature stalked its prey on vertical surfaces, tentatively bending its antenniform feelers around curves as it hunted. These feelers were in fact modified legs but were no longer used for locomotion. They had become long and thin, and articulated with many joints, forming the elegant structure that gives this arachnid its common name “whip spider.”

Whip spiders possess a diverse array of cuticular sensory structures on their antenniform legs. Among the hairs (or setae) are bristles, club sensilla, porous sensilla, rod sensilla, leaflike hairs, and trichobothria. In addition to the setae, there may be other structures present, including a pit organ, a plate organ, and slit sensilla. Among the most numerous of these cuticular sensory setae are bristles. Bristles are most likely contact chemoreceptors, able to “taste” chemical traces via an open pore at the tip of each bristle. These bristles are arranged in 5 evenly spaced rows around the circumference or the tarsi and may range in number from almost 500 in the protonymph to more than 1,500 in the adult. Approximately 500 club sensilla may also be involved in chemoreception, primarily in olfaction, as are the porous sensilla consisting of hairs perforated by numerous pores. Among mechanoreceptors are the trichobothria, the leaflike hairs, and the slit sensilla. In whip spiders, the long delicate trichobothrial hairs are found on the tibia of the whip as well as on the tibia of the walking legs. These, as well as the slit sensilla, provide long-distance mechanoreception, extremely important in detecting moving prey. In fact, the walking legs provide an important backup in this crucial aspect of hunting.

Two long, slender antenniform legs characterize amblypygids, giving them the name “whip spider.” These legs are no longer used for locomotion but are sensory in function. The antenniform legs
are also essential in intraspecific communication.

Even if the whip spider has lost both antenniform legs, it can still find and capture prey successfully by using the trichobothria on the walking legs; however, the whip spider absolutely must have trichobothria in order to locate moving prey. Once potential prey has been detected, the amblypygid orients itself facing toward it and unfolds its raptorial palps in preparation for the capture as it approaches the quarry. With a sudden lunge, the prey is grasped with the armed palps. Perhaps because whip spiders possess no venom and are somewhat delicate in physical structure, the creatures they capture are usually smaller than themselves. Crickets, moths, small lizards, and small frogs have been documented as prey of whip spiders in the wild. Once the prey has been captured, the whip spider uses its chelicerae to tear a hole in the body wall and regurgitates digestive juices into the opening. The chelicerae continue to masticate the prey into an amorphous mush while the digestive fluids break down the tissue. Like most other arachnids, the whip spider ingests only liquefied food, filtering out solid particles as the powerful phyrangeal pump and stomach suck in the predigested meal.

Amazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference

Amazing Arachnids: Fishing Spiders

Adapted from pages 296-297 of Amazing Arachnids:

Resting its front feet on the water’s surface, a Dolomedes fishing spider waits along the edge of a small, slow-moving stream. It reads every disturbance, however subtle, on the water’s surface much the way that an orb weaver spider reads the vibrations within its web. In addition to detecting motion with its feet (specifically with the metatarsal lyriform organ), it can also see quite well; its large eyes are not very different from those of its cousin the wolf spider. The fishing spider’s patience is rewarded when an immature grasshopper attempts to leap across the stream and falls onto the surface of the water. Faster than the eye can follow, the fishing spider gallops across the water’s surface and grasps the hapless grasshopper between its two impressive fangs. The spider then returns to the edge of the stream to eat the grasshopper on land, where it efficiently masticates its food and sucks down the liquefied portion until all that is left of the grasshopper is an unrecognizable crumb and a few fragments. 

Dolomedes belongs to the family Pisauridae, also known as nursery web spiders and fishing spiders. In some ways, the fishing spider is the aquatic analogue to the terrestrial wolf spider. This family includes characteristically large, handsome spiders with good eyesight that depend on their speed and strength in order to capture prey. Many of the family frequent moist habitats, but it is the genus Dolomedes that has mastered a lifestyle connected to the water. Despite the fact that some of the species in this genus reach an impressive size (Dolomedes okefenokensis has a leg span of 4 to 5 inches, or 10 to 12.7 cm), they can “row” or even rest their bodies on the water’s surface without breaking the surface tension. The water simply indents or dimples where their legs and body contact the surface. While the spider is on the surface of the water, it

An impressive predator, this mature female Tinus peregrinus fishing spider has captured a fish as large as herself.
She has carried it up into vegetation, where she will masticate and predigest the fish. She must feed out of water or the enzymes needed for predigestion will be diluted out.

is vulnerable to attack from below by underwater predators such as frogs. In this situation, the spider literally levitates by rapidly pushing all its legs downward against the water’s surface to generate the force needed to jump straight up. It then gallops to safety. If the fishing spider becomes startled or frightened by a bird or a wasp, it scrambles underwater, clinging to vegetation so it doesn’t pop back up to the surface. A thin layer of air clings to the hydrophobic cuticle and hairs on the spider’s body, giving it a lovely silvery appearance. It can remain underwater for a good 40 minutes while waiting for the danger to pass. 

Dolomedes spiders must remain vigilant while hunting, because they themselves are hunted. A spider wasp in the pompilid family, Anoplius depressipes, preys exclusively on female Dolomedes spiders. If a fishing spider sees one of these wasps nearby, it takes evasive action, fleeing from the wasp and diving under water in an attempt to escape. But the wasp does something really extraordinary. It actually dives and then swims underwater in pursuit of the unfortunate spider. Once it finds its prey, the wasp stings and paralyzes the spider. The wasp then surfaces with the paralyzed spider and drags it across the water as it skims across in a low flight trajectory. The spider is installed in the nest burrow of the wasp, and a single egg is laid on it. The wasp larva feeds on the still-living, paralyzed Dolomedes until it finally kills the spider. Then the wasp larva pupates.

Unlike the wasp, Dolomedes hunts on the surface of the water. Some authors have written that it hunts underwater, but this has yet to be clearly documented. Instead, it captures its prey primarily either at the surface of the water or on land. Despite this limitation, it can readily catch fish as they swim very close to the water’s surface. The fangs and venom appear to be highly effective in killing the captured fish almost instantly, making it easier for the spider to carry its prey across the water and onto land or up into vegetation growing at the edge of the water. Because spiders ingest only liquefied, predigested food, the fishing spider must eat its prey above the water or else its digestive fluids will be diluted or lost.

Amazing Arachnids coverAmazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference

Amazing Arachnids: Pirate Spiders

Adapted from pages 285 to 286 of Amazing Arachnids:

With infinite patience, the pirate spider Mimetus slips into the web of an orb weaver and approaches its prey. Its progress is almost imperceptible as it pauses for long minutes between each stealthy step. But eventually the pirate spider is within striking distance of its quarry. With a sudden lunge, Mimetus attacks the target, using its long chelicerae to administer the lethal bite. Immediately, it releases the victim and waits a bit, making sure that the spider victim is dead. It does not have long to wait; the orb weaver dies almost instantly from the potent venom,  which is highly effective against spiders. The pirate spider then settles down to suck out the contents of the orb weaver, leaving the cuticle of its prey almost completely intact. The web built by the orb weaver to capture food is now the platform for its own consumption.

Slow and stealthy, pirate spiders hardly seem like lethal predators at first glance. But pirate spiders have made a specialty of hunting other spiders, especially the orb weavers and the combfooted spiders (the theridiids), including even black widows. The spiders in the family Mimetidae possess extremely long front legs armed with heavy, slightly curved setae. Another spider hunter, Rhomphaea, also has exceptionally long front legs. Perhaps this is a useful adaptation when attacking a spider in its web, giving the attacker a superior reach.

Pirate spider

A Metapeira met a pirate. Incredibly slow and stealthy, the female pirate spider Mimetus hesperus slipped into the web of a small Metapeira orb weaver, taking more than an hour before getting close enough for the final lethal attack. The pirate spider then fed at her leisure.

The name Mimetidae is based on the Greek word for “imitator, actor, and impersonator.” In fact, the genus Eros is notorious for incorporating deception into its hunting repertoire, utilizing what is called aggressive mimicry. Aggressive mimicry is defined by a predator (the mimic) imitating a harmless organism (the model), thereby attracting the prey. Aggressive mimics that target more than one species of prey may have evolved highly complex repertoires of behaviors, and may demonstrate plasticity in the use of these behaviors. Staying near the periphery of the victim’s web, Eros seductively plucks the silk, imitating a courting male. When the resident spider hurries over to investigate, Eros bites her on the leg and kills her. Eros then eats not only the spider, but any eggs as well. In 1850, Nicholas Marcellus Hentz wrote, “The Mimetus … prefers prowling in the dark, and taking possession of the industrious Epeira’s threads and home, or the patient Theridion’s web, after murdering the unsuspecting proprietor.” Occasionally, though, if Mimetus becomes a little careless, the hunter may become the hunted, and the pirate spider may be killed by the resident spider and then eaten.

Although the female Mimetus seems to prefer spiders as the predominant prey, male Mimetus readily hunt other small arthropods such as gnats. The males may be seen as regular visitors on sliding glass doors at night, feeding on small gnats attracted to the light. It is sometimes difficult to imagine that this innocuous male belongs to the same species as the lethal female.

Amazing Arachnids coverAmazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference

 

Amazing Arachnids: Tarantulas

Adapted from pages 165-172 of Amazing Arachnids:

Tarantulas range in size from the largest spider in the world, Theraphosa blondi of South America, with a leg span of up to about 10 inches (25 cm), to Aphonopelma paloma, with a leg span of only 0.75 inches (2 cm).

Tarantulas also have a variety of lifestyles and behaviors, from the stereotypically solitary burrow dweller to the subsocial behavior of some communal species, such as the dwarf tarantula species Holothele (from South America) and Heterothele (from Africa). These communal spiders may cooperatively kill prey and young spiders share the kill. Circumstantial evidence suggests that even some species that live in underground burrows may have extended maternal care of young. In a number of instances, young tarantulas well beyond the third instar have been found  sharing an adult female’s burrow, leading to speculation regarding whether the mother shares food with her offspring.

Tarantula

Aphonopelma chalcodes adult male. These large males have a leg span of about 4 inches (10 cm) and are a common sight as they wander during the summer monsoon season (July and August) in southern Arizona.

The tarantulas of the southwestern United States belong to the genus Aphonopelma. These range in size from fairly large species such as Aphonopelma chalcodes, with a leg span of about 4 to 5 inches (10– 12.7 cm), to the tiny Aphonopelma paloma. A number of Aphonopelma are intermediate in size and are restricted to the mountains of southern Arizona. These tarantulas have a leg span of only about 2 inches (5 cm). The males mature in late fall or winter and may be seen as they wander in search of females even when there is snow on the ground. Because these mountain ranges are separated by barriers of low desert, many of the “sky island” populations have been geographically separated long enough that they are separate species.

One of the most common and conspicuous species is Aphonopelma chalcodes, also known as the desert blond tarantula. This handsome spider lives in an underground burrow in the low-elevation deserts of Arizona and may take about 10 years to reach maturity. The male looks markedly thinner and leggier than the female and, in addition, acquires a tibial spur on his front legs with his final molt. The males leave their burrows upon reaching maturity and go wandering in search of females. They are a familiar sight in the southern Arizona desert during the summer monsoon season, cruising at night or during the late afternoon, especially after a summer rain storm.

Hollywood has effectively exploited these fears, conjuring up giant tarantulas, deadly venomous tarantulas, and tarantulas that wipe out entire towns. But these animals have so much more to offer than cheap thrills. Their beauty and their diversity in both appearance and lifestyle defy the imagination and far surpass Hollywood’s wildest dreams. Certainly, they compel our respect, as does any predator capable of self-defense, but they also deserve our appreciation and protection.

We included a photo of one of the largest tarantulas – but what about the smallest? Head to our Instagram to see how tiny tarantulas can be. 

Amazing Arachnids coverAmazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference

Amazing Arachnids: Orb Weavers

Adapted from pages 184-186 of Amazing Arachnids:

A delight to the eye and an engineering marvel, the orb web epitomizes the stereotypical spider web. It is built in a vertical plane, with strong, nonsticky silk radiating out from a central hub like the spokes of a wheel, supporting a spiral of evenly spaced sticky silk threads. A gap in the sticky silk near the hub allows the orb weaver to rapidly climb from one side of the web to the other, depending on which side of the web a flying insect has blundered into. Some orb weavers wait in the center of the web, legs stretched out in contact with the radiating silk lines that convey the vibrations of a struggling insect. Others build a little retreat at one side of the web, maintaining contact with the radiating lines via a signal thread leading to the hub. Lying in wait in the retreat, the spider rests with one leg touching the signal line. At the first indication that an insect has been caught, the spider moves into the web and tugs at the radial lines, testing to see the general location of the prey. It then uses the nonsticky radial lines as a quick pathway leading to the insect. Once the prey is reached, the spider uses large amounts of silk to wrap and immobilize it prior to settling in for the meal.

Many orb weavers build a fresh web every night and eat the silk by the next morning. Experiments with radioactive labeling have shown that spiders are the ultimate recyclers; up to 90 percent of the old silk is recycled into the new web, and such ingestion and reuse of the silk protein can occur in as little as 30 minutes. The spiral silk of the orb weavers owes its stickiness to the addition of little beads of viscous glue along its length, like the beads of a necklace. Neither the radial threads nor the hub threads have this glue, allowing the spider easy and rapid access to all parts of its web.

An orb weaver spider

Surreal in color and form, the spiny orb weaver, Gasteracantha cancriformis, builds its web in trees and other tall
vegetation. This genus occurs primarily in the tropics; however, this particular species is also found across the
southernmost states in North America.

Some orb weavers build a web that remains in place for more than one day. Among these diurnal spiders are some that incorporate a special structure into the web, called the stabilamentum. The stabilamentum is composed of a thicker kind of silk, frequently appearing as a conspicuous white area in the web. It may look like a lace doily, or like one or more heavy zigzags in the web. Another type of stabilamentum consists of a line of silk above and below the resting spot in the hub of the web. The empty husks of insect prey are attached to this line, forming irregular clumps of detritus. Sitting motionless in the open spot in the middle of this detritus, the orb weaver Cyclosa appears to be just one more clump of debris in the stabilamentum. Camouflage protects the spider against predation by birds. Yet a different type of protection from birds may be derived from the presence of stabilamenta.

Orb weavers are more flexible in their ability to react to different circumstances than one might imagine. They build larger webs when they are hungry or if they are in areas of low prey availability than when they are well fed or in areas of high prey availability. Both web design and the timing of its construction are synchronized with the type of prey and its availability, requiring the adjustment of the spider’s circadian rhythm. In addition, orb weavers modify their approach to different types of prey in the web depending on whether the prey is potentially dangerous or not. They seem to know what kind of prey has been captured (perhaps based on the vibrations transmitted from its struggles) even before the spider physically makes contact with the prey. Some undesirable prey, such as stinging insects, are deliberately cut loose and released from the web. Other prey, like stink bugs, may be carefully wrapped so as to avoid eliciting a release of defensive chemicals until the killing bite can be administered in safety.

Amazing Arachnids coverAmazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference

Amazing Arachnids: Vinegaroons

Adapted from pages 69-74 of Amazing Arachnids:

Armed with heavy, lobsterlike claws at the front end of their bodies and shooting almost pure acetic acid out of their rear ends, vinegaroons seem to have stepped straight out of a science fiction novel. Despite their fantastic abilities, vinegaroons are perhaps the most poorly understood of the large arachnids. This may be the result of their nocturnal habits, dark nonfluorescent coloration, and the fact that they live most of their lives underground. However, the story of these enigmatic creatures is well worth the cost, albeit paid for in sleepless nights. Their story rivals and even surpasses the creations of fiction.

The common name “vinegaroon” is well chosen. The defensive spray of the vinegaroon Mastigoproctus giganteus of the southwestern United States consists primarily of acetic acid (up to 84 percent), water (10 percent), and caprylic acid (5 percent). Acetic acid is, of course, the component that gives vinegar its characteristic odor. Hydrophilic “water-loving” acetic acid in pure form simply beads up on the lipid-containing cuticle of most arthropods. But with the addition of the lipophilic “lipid-loving” caprylic acid, the spray spreads easily and penetrates into the cuticle. The caprylic acid derives its surfactant properties from a chain of 8 carbon atoms in the molecule, as compared with only 2 carbons contained in acetic acid. The acetic acid spray is produced in a pair of pygidial glands in the abdomen of the vinegaroon. Contraction of muscles in the outer layer surrounding the gland discharges the mixture as a spray from a knoblike structure called the pygidium at the base of the “tail” (called the flagellum). By bending the abdomen and rotating the knob, the vinegaroon can direct the spray with considerable accuracy, even if the target is almost directly in front of it.

As added protection, vinegaroons can defend themselves by spraying almost pure acetic acid from the pygidium, located at the base of the flagellum. By rotating the pygidium, the vinegaroon can aim the spray in almost any direction, even almost immediately in front of it. The flagellum assists the vinegaroon in accurately aiming the spray. Photo by Bruce D. Taubert.

Vinegaroons may spray repeatedly (as many as 19 times) before depleting their reserve of defensive chemicals. It takes about a day for them to recharge their reservoir. The spray has proven to serve as a deterrent to the most formidable arthropod foes such as ants. It also repels vertebrate predators such as the fierce little predaceous grasshopper mice. In contact with human skin, it may cause a burning sensation, and of course the eyes of a potential vertebrate predator such as a bird or a grasshopper mouse would be highly vulnerable to the effects of the acid.

The acetic acid is used purely as a defense weapon—not for capturing prey. A hunting vinegaroon employs tools similar to those used by scorpions for  detecting prey. A combination of sensilla (to pick up substrate vibrations) and trichobothria (to detect airborne vibrations) on the uropygid’s legs allow it to narrow down the general location of its quarry. The tiny hairs on the flagellum might also assist in this task. At the same time, the antenniform legs are extended forward, tapping the surface as the uropygid seeks out prey. Chemosensory hairs on the antenniform legs provide chemical clues as to the identity of any objects it encounters. As soon as the vinegaroon has positively identified a potential prey animal, it charges forward, grabbing with its heavy, clawlike palps. If it misses with the first try, it excitedly feels around with the antenniform legs, searching until it has once again located its quarry.

There are 4 free living instar stages before maturation, and since the young uropygid may not molt following a poor year, it may take from 5 to 7 years to reach maturity. Vinegaroons do not molt again once they are mature, and so their normal lifespan in the wild is probably in the range of 6 to 9 years. Eventually, this magnificent predator slows down due to old age, as joints stiffen and lost appendages cannot be regenerated. Perhaps even in the wild, it may actually die of old age, still a formidable predator to the end.

 

Amazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference

Amazing Arachnids: Jumping Spiders

Adapted from pages 236-247 of Amazing Arachnids:

Jumping spiders have so many pleasing qualities that it would be difficult to decide what is most admirable about these delightful little creatures. Shimmering iridescence and rich, velvety colors equal the beauty of birds and butterflies. Their fearless capture of prey and their acrobatic leaps surprise and astonish us. Their complex courtship song and dance pique our curiosity. But perhaps the most endearing aspect of jumping spiders is their enormous, forward-facing eyes, gazing at us with every appearance of intelligence and inquisitiveness.

These large, forward-facing eyes, called anterior median eyes, are indeed the key characteristic of this diurnal hunter. Jumping spiders locate their prey visually, stalking and pouncing on it like tiny cats. Unlike vertebrate systems in which one pair of eyes handles depth perception, motion detection, and detail resolution, the spider’s 4 pairs of eyes divide these tasks. Collectively, their 8 eyes create a visual system that rivals any other arthropod’s vision.

Habronattus hallani male. This species of
Habronattus is found throughout a large part of the western United States and into Mexico. It is also primarily a ground hunter.

The force of the grip is due to physical adhesion, not to suction cups or electrostatic forces. If two glass slides are overlapped with a thin film of water between them, they are difficult to pull apart because of the capillary force of the water. The scopula hairs of the spider utilize these extremely strong capillary forces. Apparently the water available in the atmosphere and on surfaces provides the necessary thin film for the end feet to grip the surface. This explains why spiders with scopula hairs can walk sure-footedly on vertical surfaces and upside down, even on glass surfaces. In jumping spiders, the tips of the tarsi (feet) have such dense claw tufts of scopula hairs that they appear to have fuzzy “toes.”

Jumping spiders make up the most diverse family of arachnids in the world, with approximately 6,000 species described so far. As one might expect with such diversity, some jumping spiders have evolved behaviors that fill extremely specialized niches. One jumping spider in Africa, Evarcha culicivora, prefers to feed on bloodfilled female mosquitoes, especially mosquitoes of the genus Anopheles, famous for spreading malaria. Another salticid, Phyaces comosus from the bamboo areas of Sri Lanka, specializes in predating the eggs and hatchlings of other jumping spiders. It is so tiny and so closely resembles a bit of dirt or debris that it can sneak into the nest of another jumping spider undetected. Yet another species, Bagheera kiplingi from Central America, has a primarily vegetarian diet—unique in the spider world. It lives in acacia trees that produce little nubbins of protein and fat from their leaf tips, as well as nectar from the base of the leaves. These provide food for the ants that in return guard the tree from caterpillars and other herbivores. The jumping spider steals the nubbins and nectar despite the ant patrols, living almost entirely on this vegetable source of protein.

In conclusion, jumping spiders rival any other group of creatures for their beauty, diversity, and complex behaviors. A combination of natural selection with sexual selection has produced an array of stunningly beautiful and surprisingly intelligent predators. The world is a richer place thanks to these diminutive gems.

Amazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference

Amazing Arachnids: The Lace-Weaver Spiders

Amazing Arachnids is a new, month-long series from Princeton Nature. Each week, we’ll highlight one of the unique arachnids found in Jillian Cowles’ richly illustrated and up-close look at the secret lives of spiders.

Adapted from page 229 of the text: 

Broad, black chelicerae and a stocky build give members of the family Amaurobiidae a powerful appearance suggestive of bulldogs. The imposing physique of these spiders contrasts with the delicate beauty of their webs, built of woolly cribellate silk. These characteristic webs give this family its name “lace-weaver spiders” or “hacklemesh weavers.” The cribellate silk of the web radiates out from a tunnel retreat, where the spider lies in wait. Insects become tangled in these hackled threads, giving time for the spider to rush out from its hiding place and catch the prey.

Amaurobius has a truly remarkable natural history in regard to its reproduction. In the case of Amaurobius ferox (an introduced species from Europe reportedly found in southern California), the mother spider lays her first clutch of eggs and stays nearby to guard them until the babies hatch. This maternal behavior is consistent with many other species of arachnids and is therefore hardly noteworthy. But then it gets interesting. After the spiderlings emerge from the egg sac, they interact with their mother, and she is induced by this interaction to lay a second clutch of eggs. This time, the eggs are laid before they are mature, and consequently this clutch of eggs serves as food for the spiderlings that hatched from the first clutch. This is referred to as trophic egg laying and is a strategy employed by several other species of animals, including some species of poison dart frogs. The spiderlings that receive this food are heavier and have a higher survival rate than spiderlings deprived of the trophic egg meal.

Callobius arizonicus. Callobius are found in cool areas, such as the mountains of Arizona and the forests of California.

But the mother spider’s sacrifice does not end there. The mother and her offspring interact further, and this time she actually appears to solicit her babies to feed on her. This the babies do, collectively killing and feeding on their mother. This matriphagy appears to be regulated by the life stage of the spiderlings, the reproductive state of the mother, and the behavioral interactions of the mother and her young. The spiderlings derive considerable benefit from this behavior. They are heavier and larger at the time they disperse compared with spiderlings deprived of their mother as food, including groups of spiderlings given an abundance of other prey to eat.

Finally, the matriphagous spiderlings have a longer period of social behavior, compared with the nonmatriphagous spiderlings. The subsocial spiderlings live together through several instar stages on the web of their mother, cooperatively killing prey and sharing it. The maternal web appears to provide a superior platform for the offspring to detect and cooperatively kill prey, as compared with webs that the spiderlings construct themselves. Prey that would be too large for one or two spiderlings to overcome is killed by groups of spiderlings, and that prey is shared even with those that did not take part in that particular kill. The spiderlings appear to use coordinated teamwork to subdue prey that is up to 10 times the size of any individual spiderling. Cooperative prey capture increases predation efficiency and survival of all the spiderlings.

Most of the members of the family Amaurobiidae live in cool, moist habitats, making their webs under debris, in caves, or in the nooks and crannies of trees. California boasts the greatest diversity of these spiders in the United States. In the arid southwestern states, Callobius arizonicus lives principally at higher elevations where it is cooler and moister. Found under rocks and dead wood, several individual Callobius spiders may share a single shelter. Only centimeters may separate their webs, indicating some degree of tolerance between individuals of the same species. Also like Amaurobius, Callobius guards her egg sac, which is produced in the shelter of her refuge. But in the case of Callobius, it is unknown whether the mother spider feeds her young.

 

Amazing Arachnids
By Jillian Cowles

The American Southwest is home to an extraordinary diversity of arachnids, from spitting spiders that squirt silk over their prey to scorpions that court one another with kissing and dancing. Amazing Arachnids presents these enigmatic creatures as you have never seen them before. Featuring a wealth of color photos of more than 300 different kinds of arachnids from eleven taxonomic orders–both rare and common species—this stunningly illustrated book reveals the secret lives of arachnids in breathtaking detail, including never-before-seen images of their underground behavior.

Amazing Arachnids covers all aspects of arachnid biology, such as anatomy, sociality, mimicry, camouflage, and venoms. You will meet bolas spiders that lure their victims with fake moth pheromones, fishing spiders that woo their mates with silk-wrapped gifts, chivalrous cellar spiders, tiny mites, and massive tarantulas, as well as many others. Along the way, you will learn why arachnids are living fossils in some respects and nimble opportunists in others, and how natural selection has perfected their sensory structures, defense mechanisms, reproductive strategies, and hunting methods.

  • Covers more than 300 different kinds of arachnids, including ones new to science
  • Features more than 750 stunning color photos
  • Describes every aspect of arachnid biology, from physiology to biogeography
  • Illustrates courtship and mating, birth, maternal care, hunting, and defense
  • Includes first-ever photos of the underground lives of schizomids and vinegaroons
  • Provides the first organized guide to macroscopic mites, including photos of living mites for easy reference