Spiders

The High Life, animal species

In the last blog, we investigated the conditions and constraints of living at high altitudes, generally above 10,000 feet. A few physiological adaptations listed included enhanced breathing and blood supply to get more oxygen to the body, internal temperature regulation allowing some mammals to adjust to a colder environment, and smaller plants requiring less moisture and having a short growing season.

^{Common springtail, Orchesella cincta, by Mvuijlst, Feb 2009}

^{Springtail, Isotoma caerulea, by Andy Murray, Jul 2014}

The Himalayan jumping spider, Euophrys omnisuperstes, is generally found above 22,000 feet, living among rock crevices and feeding on stray insects blown upward by rising mountain winds. The spider also feeds on springtails, Collembola, once considered an insect but now classified as a free-ranging hexapod. These tiny organisms have antifreeze compounds in their blood, enabling them to live in higher, colder habitats.

Reptiles from four lizard species have been found living in higher elevations. Two species of iguana in the genus Liolaemus live in Bolivia; a third iguana species, Liolaemus tacnae, lives in Peru; and an Asian lizard, Phrynocephalus erythrurus, lives on the Tibetan plateau. All were found between 16,000 feet and 18,000 feet, but very little is known about them since these areas are difficult to access for study.

^{Golden eagle, Aquila chrysaetos, by Giles Laurent, Dec 2021; Andean condor, Vultur gryphus, by Bastihitzi, May 2013; Alpine chough, Pyrrhocorax graculus, by Jim Higham, 2008}

Birds can be found living near mountain tops year-round. The Alpine chough, Pyrrhocorax graculus, lives in social flocks from the Alps to the Himalayas. Standing 15″ high with a 30″ wingspan, they have black feathers with distinct yellow beaks and red legs. They eat insects and berries in summer, but have become well-adapted to scavenging in winter, especially around ski resorts. The Andean condor, Vultur gryphus, another social bird, roosts on cliffs and outcrops above 16,000 feet. The steep terrain provides additional protection from potential predators. Golden eagles, Aquila chrysaetos, are found world-wide in many habitats. In the mountains, they hunt marmot, hare, and young goats at lower elevations, but nest in eyries, large cliff-hugging nests at higher elevations. With wingspans up to seven feet, they can dive at speeds of up to 150mph over unsuspecting prey.

^{Left top to bottom: Common crane, Grus grus, by Savithri Singh, Feb 2020; Whooper swan,Cygnus cygnus, by KyoichiNarukami, Japan, Jan 2012; Bar-headed goose, Anser indicus, by J.M.Garg, India, Mar 2000; Ruppell’s Griffon Vulture, Gyps rueppellii, by Lip Kee, Kenya, Aug 2008}

High altitude bird species with physiological adaptations for breathing and blood supply include those whose migration routes take them over the world’s highest mountain ranges. Ruppell’s Griffon Vulture, Gyps rueppellii, with an 8-foot wingspan, has been observed at altitudes exceeding 36,000 feet over the Ethiopian Highlands of Central Africa. The common crane, Grus grus, lives across eastern Europe and northern Asia, migrating over the Alps to Africa, India and southern China. The bar-headed goose, Anser indicus, and the whooper swan, Cygnus cygnus, both live in south Asia and migrate over the Alps to central and sub-Arctic Asia to breed.

^{Above: Large-eared pika, Ochotona macrotis,}
^{by Karunakar Rayker, Ladakh India, Feb 2008}

^{Right: Snow leopard, Panthera uncia, by Vassil, Aug 2007}

The heights of the Himalayas support mammals that can concentrate their hemoglobin and allow the blood to carry more oxygen, avoiding issues with hypoxia, a shortage of usable oxygen in the body. Species with this physiological adaptation include large-eared pika, Ochotona macrotis, living above 7,700 feet up to 20,000 feet; wild yak, Bos mutus, which have larger heart and lungs than domesticated yaks; and the snow leopard, Panthera uncia, living above 3,000 feet up to 18,000 feet. The snow leopard has short, heavily furred limbs and a long, heavy tail for use as a blanket. Its large nasal cavity and strong chest allows more oxygen to be taken in with each breath.

^{Ethiopian wolf, Canis simensis, by Charles J. Sharp, Ethiopia, Dec 2017; Mountain goat, Oreamnos americanus, by Darklich14, Colorado, Aug 2009; Tibetan argali, Ovis ammon, by DonArnold, Jurica-Suchy Nature Museum, Mar 2026; Guanaco, Lama guanicoe, by Charles J. Sharp, Chile, Oct 2025; Yellow-rumped leaf-eared mouse, Phyllotis xanthopygus, drawing by Charles Darwin, 1832}

Mountain goats, Oreamnos americanus, can climb steep cliff faces with hooves that grip ledges and rock surfaces in the Rocky Mountains. The yellow-rumped leaf-eared mouse, Phyllotis xanthopygus, feeds on grains, seeds, roots, and insects in the Andean Mountains of Chile, living at altitudes to 22,000 feet. Guanaco, Lama guanicoe, a member of the camel family, lives in the Andes up to 13,000 feet and has about four times as many red blood cells as a human does. The Ethiopian wolf, Canis simensis, is an endangered species living up to 15,000 feet in central Africa with populations fragmented by pressure from human farming activities. Tibetan argali, Ovis ammon, is a wild sheep found in the Altai Mountains of Mongolia up to 19,000 feet. The ewes and lambs prefer steep, treacherous slopes as protection against predators.

Scientists continue to study species in these habitats to learn more about their specific adaptations and survival abilities in a harsh environment. You can learn more by visiting zoos or nature museums near you to investigate these fascinating species.

Creepy Critters

A lot of creepy critters are starting to show up in my neighborhood as Halloween approaches. Many people are putting out scary pumpkins, bats, spiderwebs, and spiders. There are about 3,000 species of real spiders in North America, and all spiders have fangs that inject venom used to paralyze or kill their prey.

Spider web house by Stephanie Wallace, Oct 2007

Spiders are normally quite timid and must be threatened or provoked before they will attack a species larger than themselves. All spiders will bite, but most species do not have teeth that are large enough to break human skin. Of those that can bite through our skin, only four species dangerous to humans are found in North America. They belong to two groups, the widow spiders with three species in North America and the recluse spiders with eleven species in North America.

Widow spiders are all commonly called black widows, but they are actually three different species located across North America and include the western species, Lactrodectus hesperus, the northern species, Lactrodectus variolus, and the southern species, Lactrodectus mactans. In northern Illinois, the northern widow is a small species between 1/8″ and 3/8″ long. Males have long abdomens with white and red markings while females have more rounded abdomens with a red hourglass marking on their underside.

Northern black widow, *Lactrodectus variolus*, male by Judy Gallagher, May 2018

Northern black widow, *Lactrodectus variolus*, female by Andrew Hoffman, May 2012

Widow spiders are shy and tend to remain hidden under logs and stones, or just inside entrances to animal burrows. During autumn, as temperatures drop, they will move inside if possible and are often encountered under furniture, boxes, or discarded items that are not often disturbed. Webs are funnel-shaped and provide for adults and eggs. Once eggs are laid, the female will rarely leave the eggs untended, and will aggressively protect them from all harm, attempting to bite anyone that disturbs her or the eggs.

Black widows tend to flee rather than bite, unless they are protecting eggs. Only the females bite and their venom is especially dangerous to humans, but bites are not painful and may not even be noticeable at first. Severe stomach cramping develops within an hour or two and breathing may become difficult. Despite the uncomfortable effects, black widow bites are lethal in less than 1% of cases.

The brown recluse, Loxosceles reclusa, is the most widespread of the recluse spiders, and is often found in or around human dwellings. Other recluse species are found in very limited areas. Their favorite outdoor spots are under boards, stones and log piles, but they are most often found inside in quiet areas on the floor or behind furniture. Adult spiders are a light yellow-brown with a dark violin-shaped marking on their back. Adults are between 1/4″ and 1/2″ long with long, thin legs that can be three to four times the length of their body.

Brown recluse, *Loxosceles reclusa*, by Mike Keeling, Jan 2008

Recluse spiders are not aggressive and will only bite when disturbed. Most bites occur when the spider is caught in an article of clothing that is picked up off the floor, startling the spider. Once bitten, the wound develops a crust with a red zone around it. The crust may fall off rather quickly but leaves a crater behind that may take several months to fully heal. Although their bite may cause tissue damage, there have been no confirmed deaths in the United States.

Halloween is a special time of year and can be a fun time with scary creatures and other haunts. The Juricha-Suchy Nature Museum is hosting its 13th annual Creepy Critters Halloween Open House on October 26th (for info, please call (630) 829-6546 or email JuricaSuchyMuseum@ben.edu). I hope you get out for some trick-or-treating of your own, and let the real spiders live quietly in their own habitats.

Forest Litter, Critters to See

Last week, we started to look at the forest floor and the litter covering it, composed of leaves, dead wood, animal carcasses and other organic waste. A complex community of organisms thrives in this habitat, working to return the nutrients from the litter back to the soil to be used again as food for green plants. The first layer of this community consists of decomposers. This week, we investigate several other layers.

Forest floor & rotten log by DonArnold, Sep2022

Many species can be spotted among the litter, but observing them takes patience. Carefully sorting through leaf litter is a skill learned through practice. Overturning decomposing logs and probing through rotting bark will yield great results if done slowly and without great disturbance to the animals present. Animals can be observed with your eyes, a hand lens, or a microscope.

Using your eyes, there are several species that like moist conditions and are easily found under decaying logs. Many are very active after an autumn rain. Some of the more abundant species are:

Slugs are a type of mollusk with a soft, slimy body that leave a slime trail wherever they go on their nighttime feeding excursions. They eat decomposing leaf litter and animal remains.

Snail, Maple Grove by DonArnold, Sep2022

Snails, another mollusk, are covered with a hard shell for protection from predators and to help retain moisture. They also eat decomposing vegetation and animal remains.

Isopods, also known as wood lice or pillbugs, must have moist conditions because they breathe using gills. Often found under logs after a rainfall, they move quickly using their 14 pairs of legs. There are several hundred species found in field and forest habitats.

Pillbug, *Armadillidium vulgare*, by Dann Thombs, Dec 2010

Millipedes are segmented and covered by an exoskeleton. Feeding on litter and animal remains, they can be found in any slightly wet area. Millipedes protect themselves when threatened by rolling up into a tight ball.

Millipede, Maple Grove by DonArnold, Sep2022 (3)

Millipede defense, Maple Grove by DonArnold, Sep2022

Several species can be found in any litter conditions. Many are predators, hunting and feeding on other animals. Some often found in our forests include:

Centipedes may look like millipedes, but are predators, eating many smaller insects. The first pair of legs by their head are modified into sharp, poisonous claws used to capture and stun their prey.

Spiders have four pairs of legs, no antenna, simple eyes, and powerful jaws with poison glands. The injected toxin liquifies the soft tissues inside the victim’s body, allowing the spider to suck them out. Many species, including the popular wolf spider, are ground dwelling, digging burrows and hunting by night.

Paperbark spider, *Maratus pavonis* by Jean&Fred Hort, Sep 2015

Harvestmen, also known as daddy long legs, are similar to spiders. They have four pairs of very long legs. When disturbed, they will wave the front two pair around to ward off another predator. They feed on small insects and decaying plants and tend to hunt in groups, mostly at night.

Harvestmen, *Phalangium opilio*, by Dann Thombs, Sep 2007

Next we will investigate what a hand lens can reveal about some of the most numerous inhabitants.

Orb Weavers

Argiope aurantia, a large spider with black and yellow markings, is a common visitor to many gardens. I watched one in our garden weave a new web. The spider started by attaching a strand of silk to an anchor point about halfway up a sunflower stalk. Then the spider dropped downward, releasing a strand of silk behind it until reaching a new level. It attached the strand to a single point and doubled the strand back to the beginning point. It repeated this process to several new points around the first anchor, eventually creating a pattern that looks like the spokes of a wheel. Each strand is stretchy, and as soon as it leaves a strand, its weight having stretched it downwards, the strand snaps back to a taut line between its two end points. The spider then starts to make a spiral from the center point working outward.

Orb-weaver laying tripline by Pepperberryfarm, 2018

Spiders are classified by the type and shape of the web they weave. Funnel weavers make a cone of dense silk walls that taper downward directing the prey to the bottom where the spider waits. Others spin a variety of silk strands with no discernible pattern. Orb-weavers, like the one described above, construct a large circle with spokes radiating out from the center. Hunting spiders do not weave webs at all, preferring to stalk and chase their prey.

Orb-weavers hard work, by Julie Falk, 2016

All spiders produce silk for use in reproduction, web-building, comfort, and moving around their habitat. Spiders can produce two kinds of silk strands, ones that are dry and ones that are tacky. After laying their eggs, females will use tacky silk to wrapped each egg into a silk sac for protection and warmth. Burrowing spiders use strands to line the inside walls of underground dens. Dry strands become draglines used to climb on or hang from when moving from one perch to another.

Black & Yellow Garden Spider, Argiope aurantia, with prey by Judy Gallagher, 2019

The spokes of an orb-weavers web are made from dry silk strands. The spiral wound from the center across all the spokes in several circles, each larger than the previous one, are made from tacky strands. Insects encountering the web by crawling or flying into it get caught by the tacky strands and are trapped. A single dry strand called a trip line runs from the center of the web to the spider sitting quietly underneath the web. When the struggling insect vibrates the web, the trip line signals to the spider to come out, biting the insect to inject venom, and wrapping its prey in more silk. The prey is left hanging in the web for a later meal.

Leucauge decorata, Silver orb spider, on dragline by Frank Starmer, 2007

Orb weavers and their webs are easy to find. They eat many insects in our gardens and are a natural form of pest control. They make great subjects to observe to learn many of their behaviors including building webs, catching prey and feeding. In summertime, you may also observe courtship, mating, and egg-laying activities. Watch for these easy to find and fascinating garden companions!

Spiders are omens of good luck, and the bigger they are, the more luck for you. If you see a spider on Halloween, it means that a deceased loved one is watching over you. According to folklore, spiders have mystical powers with their ability to spin both physical and magical webs. The name spider is from “spinder” a reference to its spinning ability. The Greek goddess Arachnea was jealous of her rival, the goddess Athena and challenged her to a silk spinning contest. When Arachnea lost, Athena turned her into a spider destined to spin silk forever. There are more than 600 species of spiders in Illinois with about 60 of those common to northern Illinois. Let’s take a closer look at spiders and their abilities.

Spiders are part of the largest phylum of animals on earth: arthropods, which include crustaceans, insects, myriapods (millipedes and centipedes) and arachnids (spiders, scorpions, mites and ticks). Spiders are characterized by having eight legs and two body parts, the cephalothorax and the abdomen, connected by a narrow portion called the pedicel.

We may characterize the cephalothorax as the head, with the spider’s face in front, mouth at the bottom, and all eight legs attached to its underside. Internally, the cephalothorax contains the venom gland, the brain and the sucking stomach. At the top of the face are six to eight simple eyes arranged in two rows from left to right. Each eye is a single lens, but all can detect color, movement, shape and size. Below the eyes are two vertical jaws lined with teeth and tipped with fangs. The fangs are used to inject both poison to disable and kill a victim and enzymes to break down a victim’s internal tissue to a liquid form. Located below the jaws is another pair of appendages called pedipalps. These are used when holding prey and feeding and are used in mating on fully grown adult males.

The abdomen contains all remaining organs including heart, intestines, book lungs and trachea, ovaries and silk glands. The abdomen may be long and thin or large and bulbous and is often colorfully marked. These distinctive colorings are useful for species identification. At the very back of the abdomen are three pairs of spinnerets. Each one attaches to an internal silk producing gland. Silk is a liquid mixture of proteins, which when exposed to air, dries immediately to a threadlike, elastic material. It can be stretched up to three times its original length, and the tensile strength is greater than that of solid bone. Each gland may produce a different type of silk. The spider uses silk, both sticky and non-sticky strands, to form webs. A web may be designed as a sheet, a funnel, a circular orb or in an irregular jumble of strands. Other uses for silk are for wrapping prey for later consumption, creating the outer covering of an egg sac, or to create a shelter. Silk is used in two ways for movement. One is to create a dragline, which a spider attaches to an anchor point, such as a tree limb or house eave, and uses it to lower themselves. The second movement, used by immature spiders to leave home, is called a balloon string. The young spider points its abdomen skywards and shoots out a set of three threads in a triangle pattern designed to catch the wind and fly them to new territory. Ballooning usually takes the spider several inches or feet to the next branch, but it has been known to transport a spider over many miles. The last use is to create a sperm web, which I will discuss below. Silk is reusable, and all spiders consume their webs after each use, returning the proteins to liquid form available to be re-used within minutes.

All spiders are predators and hunt for food. Favorite foods include other arthropods as well as other spiders. Adult females are considerably larger in size than adult males who must impregnate the female without getting eaten. When males reach sexual maturity, the ends of their pedipalps enlarge to form a sperm holding chamber. A sperm web is formed from silk and sperm is laid on this web to be taken up into the pedipalps where it is stored until needed. To avoid being eaten, males will court a female to clearly establish his intentions. For species with poor eyesight, the male will walk onto a female’s web using an intricate pattern of vibrations that indicates he is not prey. For species with good eyesight, the male will get in front of the female and perform a courtship dance or combination of poses.

Crab Spider in Yellow by Judy Gallagher, c-2016

Once the female accepts the male, his sperm must be deposited from each pedipalp into the epigynum, an opening on the bottom of her abdomen leading to the ovaries. He will climb on the back of her abdomen, reach around and deposit sperm from both pedipalps and leave. Males may mate with more than one partner, but most will die shortly after mating. Eggs are produced and fertilized during the summer, then deposited in an egg sac. The egg sac may be carried around by the female or attached to the edge of her web. Egg sacs may contain from one to several hundred eggs. Eggs will hatch within a few weeks, depending on the species. Spiders are born blind but will grow functioning eyes within several days of hatching. The young stay close to the egg sac to use it for nourishment until they can see and begin to hunt for themselves. The young will molt from four to twelve times, growing functional eye tissue, fangs and spinnerets during subsequent molts. Any lost body parts, such as a leg, can also be regrown during a molt, however once they are adults, they will never molt again. The molting process normally takes several months and many species will spend their first winter between molts, having their final molt during spring of the following year.

Following the first or second molt, juveniles are able to feed themselves and will begin to hunt on their own. As predators, they quickly find that other spiders make good meals, and cannibalism in large hatches is a reality. In general, spiders are either active hunters, typically found in species with good eyesight, or web weavers, typically those species with poorer eyesight. For web weavers, all prey is caught in a web. Prey thrashes about getting more entangled until the prey tires. Spiders can tell from the vibrations at which point they can safely move in and using their fangs, inject venom to further subdue and kill the victim. At the same time, enzymes are also injected to break down internal tissues into liquid form. Active hunters will lie in wait or chase down prey. Many active hunters use coloration to blend in with flowers and other vegetation while hunting. Some species, including crab spiders in our area, can change their body colors to match different flower colors. Spiders eat all meals in a liquid state and have powerful stomach muscles that pull all liquids into their stomach.

Crab Spider in White by Michael Figiel, c-2016

All spiders produce venom. In northern Illinois, there are only two species that may pose a serious threat to humans. They are the Brown Recluse, Loxosceles reclusa and the Northern Widow, Latrodectus variolus. Both of these species are native to areas farther south and are not commonly found in northern Illinois. It is thought that they only occur when brought into an individual home from elsewhere. Spiders, in general, including these two species, are not known to bite unless provoked. Most spiders live an average of one to two years, although some species in the tropics may live up to 20 years. Their most effective predators are found among wasps. Two wasp families will repeatedly sting the spider until it is paralyzed, then drag it off to their nests. Instead of eating the spider, the wasps lay an egg on the spider’s abdomen, and when the egg hatches, the larva will feed on the still living spider until it dies and the wasp pupates. Other predators include fish, frogs, toads, salamanders and other spiders. Spiders are one of our gardens most beneficial inhabitants, eating many of the garden’s numerous flower and vegetable pests.

Winter is the time of least activity, but warmer days or when the sun is providing radiant warmth, you can observe spiders being active even on top of the snow. Most overwinter in leaf litter, under bark or in hollow logs or crevices. If they decide to move inside with you and you prefer they didn’t, they can easily be captured with a paper cup and a lid (3×5 cards work well) and released outdoors. However, they will do a good job patrolling insect pests, including aphids on indoor plants, as well. There are many good books and websites to get more information. A couple of my favorites include “Good Garden Bugs” by Mary M. Gardiner, Ph.D.; “Spiders of the North Woods” by Larry Weber, part of the North Woods Naturalist Series; and a video of ballooning on the Science Magazine website found at watch-ballooning-spider-take-flight.