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What species is this large-ish spider?

What species is this large-ish spider?



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Last night I came across this spider outside my house (costal Southern California). It was bigger than any I'd seen before, about 2.5 or maybe 3 inch legspan, maybe just under an inch for the body length. It is a brown-gray color, the cephalothorax has two dark brown stripes, and some mean looking fangs. Can anyone identify it?


Looking at this reference "Frequently synanthropic spiders of Southern California", I would have to say that it is possibly a grass spider. (Please someone correct me if I am wrong).

Beautiful looking specimen!


Yes, it's definitely an adult male Agelenid - one of the funnelweavers. More specifically, one of the outdoor species known collectively as Grass Spiders. The nice long exhaust-pipe spinnerets at the back tell you that, and the racing-stripe pattern on the body. The big boxing-glove palps hanging in front of the face tell you it's an adult male, which is why it was wandering around looking for love. I'm not familiar with the California species, but this is probably one of the western Agelenopsis species. https://bugguide.net/node/view/2001


Wolf spider

Wolf spiders are members of the family Lycosidae, from the Ancient Greek word " λύκος " meaning "wolf". They are robust and agile hunters with excellent eyesight. They live mostly in solitude and hunt alone, and do not spin webs. Some are opportunistic hunters, pouncing upon prey as they find it or even chasing it over short distances. Some wait for passing prey in or near the mouth of a burrow.

Wolf spiders resemble nursery web spiders (family Pisauridae), but wolf spiders carry their egg sacs by attaching them to their spinnerets, while the Pisauridae carry their egg sacs with their chelicerae and pedipalps. Two of the wolf spider's eight eyes are large and prominent this distinguishes them from nursery web spiders, whose eyes are all of roughly equal size. This can also help distinguish them from the similar-looking grass spiders.


A new species of spider

During a research stay in the highlands of Colombia conducted as part of her doctorate, Charlotte Hopfe, PhD student under the supervision of Prof. Dr. Thomas Scheibel at the Biomaterials research group at the University of Bayreuth, has discovered and zoologically described a new species of spider. The previously unknown arachnids are native to the central cordillera, not far from the Pacific coast, at an altitude of over 3,500 meters above sea-level. In the magazine PLOS ONE, the scientist from Bayreuth presents the spider she has called Ocrepeira klamt.

"I chose the zoological name Ocrepeira klamt in honour of Ulrike Klamt, my German teacher at high school. The enthusiasm with which she pursues her profession and the interest she shows in her students and in literature are an inspiration to me," says Charlotte Hopfe.

The cordillera in Colombia is famous for its unusually large variety of species. The habitats of these species are distributed at altitudes with very different climatic conditions, vegetation, and ecosystems. The Bayreuth researcher has collected and zoologically determined specimens of more than 100 species of spider in these habitats. In doing so, she was mainly in a region that has only been accessible to researchers since the end of civil war in Colombia in 2016. She discovered the new spider, which differs from related species in the striking structure of its reproductive organs, at altitudes of over 3,500 meters above sea-level. In the identification of this and many other spider specimens, Hopfe received valuable support from researchers at Universidad del Valle in Cali, Colombia, with which the University of Bayreuth has a research cooperation. Colombia has been identified as a priority country in the internationalization strategy of the University of Bayreuth, which is why it maintains close connections with several Colombian universities.

The study of spiders from regions of such various huge climatic and ecological variety may also offer a chance to find answers to two as yet unexplored questions. It is not yet known whether temperatures, precipitation, or other climatic factors influence the evolution of spiders, or the properties of their silk. For example, is the proportion of species with extremely elastic silk in the lowland rainforest higher than in the semi-desert? And it is also still unclear whether the properties of the silk produced by a species of spider are modified by climatic factors. Would a spider living in the high mountains, such as Ocrepeira klamt, produce the same silk if it were native to a much lower region of the cordillera? The answer to these questions could provide important clues as to the conditions under which unusual spider silks develop.

Along similar lines, it would also be interesting to explore whether there are spider silk proteins which, due to their properties, are even more suitable for certain applications in biomedicine and biotechnology than silk proteins currently known. "The greater the variety of spider silks whose structures and properties we know, the greater the potential to optimize existing biomaterials and to develop new types of biomaterials on the basis of silk proteins," Hopfe explains.

Charlotte Hopfe's research was funded by the German Academic Exchange Service and the German Academic Scholarship Foundation.


Seven New Species of Australian Peacock Spiders Discovered

Maratus azureus. Image credit: Joseph Schubert.

Maratus is a relatively large genus of jumping spiders in the family Salticidae.

Members of this genus are commonly referred to as peacock spiders due to the males’ colorful and usually iridescent patterns on the upper surface of the abdomen often enhanced with lateral flaps or bristles. By contrast, females are cryptic in appearance and lack bright colors.

Peacock spiders are tiny spiders with a total body length mostly around 4-6 mm, and are most noted for their spectacular courtship display.

The genus now contains 85 recognized species, all of which — except Maratus furvus from China — are endemic to Australia.

Upper row, left to right: Maratus constellatus, Maratus inaquosus, and Maratus laurenae. Bottom row, left to right: Maratus noggerup, Maratus suae, and Maratus volpei. Image credit: Joseph Schubert.

In a paper published March 2020 in the journal Zootaxa, Schubert described seven new species of peacock spiders:

(i) Maratus azureus, Maratus constellatus, Maratus laurenae, Maratus noggerup, and Maratus suae from Western Australia

(ii) Maratus volpei from South Australia

(iii) Maratus inaquosus from Victoria.

“Some of these species were discovered by citizen scientists who documented the localities and sent images to me – their help is so important for this kind of research,” Schubert said.

“Males of these new species have remarkable iridescent colors and patterns on their abdomens, an identifying feature of peacock spiders used in their courtship displays.”

“I would have to say Maratus constellatus is my favorite by far — it’s such a nice looking species, the pattern reminds me of The Starry Night by Van Gogh. Plus I traveled a very, very long way to find it,” he added.

Schubert believes this is just the start of an ever-growing list of new discoveries about peacock spiders.

“I don’t think we are anywhere near done yet, considering how many species have only recently been discovered and how many sites are yet to be explored — I’m still actively on the hunt for new species of peacock spider.”

Joseph Schubert. 2020. Seven new species of Australian peacock spiders (Araneae: Salticidae: Euophryini: Maratus Karsch, 1878). Zootaxa 4758 (1): 001-044 doi: 10.11646/zootaxa.4758.1.1


Spiders

Spiders are closely related to mites, ticks and scorpions and are collectively known as arachnids.

Both spiders and insects are arthropods, meaning their skeletons are on the outside of their bodies (exoskeleton).

Web-building spiders construct webs in calm, undisturbed places to capture their food.

  • They live in or near their web and wait for food to come to them.
  • They generally have poor eyesight and rely on sensing vibrations in their web to find prey.
  • Some species of web-building spiders can survive and reproduce well indoors and outdoors.

Hunting spiders are outdoor spiders that may wander indoors accidentally.

  • They do not make webs to capture food.
  • They are quick and have good eyesight that helps them to capture prey.
  • Active hunters search for and chase their prey.
  • Passive hunters lie in wait and capture prey as it approaches.
  • They live outdoors but may enter into homes accidentally, particularly in the fall.
  • They do not survive well indoors and usually do not reproduce indoors.

Spider biology and behavior

How to tell a spider from an insect

Spiders Insects
Body regions 2: cephalothorax and abdomen 3: head, thorax and abdomen
Legs 8 6
Eyes Simple, usually 8 (rarely 6) Compound, 2
Wings None 4 (sometimes 2 or none)
Antennae None 2
Mouthparts Chelicerae (fangs) Mandibles (jaws)

Spider behavior and spider bites

  • All spiders inject venom through their hollow fangs into living prey to disable the prey.
  • They liquefy their food with digestive fluids and then suck in the digested food.

Silk is produced by all spiders as a liquid in specialized structures called spinnerets located at the tip of the abdomen. Silk hardens after contact with air.

Spider bites

Spiders very rarely bite people. Most spiders are harmless to people and are incapable of biting, even when coaxed.

Most people and even medical doctors over-diagnose “potential spider bite” based on symptoms such as redness, swelling, cramps, severe pain, or even necrotic lesions. These are usually caused by other factors including diseases or medical conditions and bacterial skin infections.

Neither black widow spiders or brown recluse are native to the upper Midwest and are rarely encountered.

Descriptions and pictures of different spiders

Open a drawer to see pictures and descriptions of common spiders found in Minnesota. Sizes given for each spider represent the length of the body not including legs.

Cobweb spiders are members of a large group called the comb-footed spiders and are very common both outdoors and indoors.

They are brownish or grayish small to medium-sized spiders (about 1/8- to 3/8-inch long) and have a rounded abdomen and a small cephalothorax.

They do not move a lot and build irregular, tangled webs for which the group is named.

Webs are built in undisturbed, out-of-the-way places such as wood and stone piles and in quiet areas of buildings such as basements.

A common type of cobweb spider found indoors is the American house spider (common house spider). It is grayish to brownish with chevron-like markings on its abdomen and a body length of over ¼ inch.

It builds a loose tangle of cobwebs in secluded and undisturbed areas of the house such as basements and crawl spaces.

Cellar spiders are common in dark secluded places such as crawlspaces, basements and cellars.

Cellar spiders are 1/3 to 1/4 inch long, pale gray to light tan in color and have long delicate legs (resembling the daddy-longlegs).

The cellar spiders build a loose, irregular web in corners near the ceiling or floor.

Orb weaver spiders (Araneidae) are commonly seen outdoors in gardens, fields, and landscapes, but are rarely found indoors.

  • Orb weaver spiders make the typical spider web of concentric circles and radiating lines.
  • They range in size from small to large (1/8- to 1-inch long) and are found in a variety of colors.
  • Orb spiders have large, swollen-looking abdomens, including some that are oddly shaped.
  • Despite their large size and bright colors, orb weaver spiders are not dangerous.

The barn spider is large (4/5-inch long) and yellow and brown in color. The barn spider is the model for Charlotte in E.B. White's famous book, Charlotte's Web.

The marbled orb weaver spider is a striking spider that attracts attention because of its typical bright orange color, though specimens vary from orange to beige to pale yellow and white.

Orb weavers do not do well when they fall to the ground. They move very slowly and have very poor vision, even for a spider.

They are extremely unlikely to bite people.

Argiope (ar-JYE-o-pee) spiders or garden spiders are also orb weavers. The large, black and yellow spiders usually are found in late summer in the center of big, round, flat webs. They have bodies measuring one inch long and, counting their legs, can be several inches in length.

There are two common species in Minnesota, the black and yellow argiope (Argiope aurantia) and the banded argiope (Argiope trifasciata).

The black and yellow argiope has a black body and yellow markings on its abdomen, somewhat resembling flames.

The banded argiope has a series of thin yellow, white, and black transverse (side to side) bands on its abdomen. Garden spiders are typically found building their webs in gardens or in tall grassy areas.

People assume because these spiders are large that they must be dangerous to people. They actually are very shy (as nearly all spiders are). They stay in their webs, eating insects they capture and rarely, if ever, are found off of them.

These spiders are not dangerous to people and should be left alone.

Funnel weaver spiders are generally brownish or grayish with stripes near the head and a pattern on the abdomen.

They have long spinnerets and are moderate-sized (¾-inch long).

They produce a flat, horizontal web with a small funnel-like retreat off to one side.

Webs are commonly built on the ground, around steps, window wells, foundations, and low shrubs.

Barn funnel weavers (a type of funnel-web spider) have a pair of dark stripes behind the head and may build webs in corners and closets indoors.

Grass spiders (a common funnel weaver) build their horizontal webs in the short grass of lawns. They have three light colored and two dark colored stripes behind the head.

Hunting spiders (do not build webs)

Wolf spiders are moderate to large-sized spiders (1/4- to 1-inch long) with dark brown and slightly hairy bodies.

They are found on the ground or under stones in a variety of habitats, such as woodlands, grassy meadows, beaches, landscapes, gardens and fields. Some even live underground.

They commonly hunt during the day or at night when it is warm.

Wolf spiders are alarming because of their large size and rapid movements. They are not aggressive.

Sac spiders are normally found on foliage or on the ground. They are small to medium-sized spiders (1/5- to 2/5-inch long) and are usually yellowish or light-colored.

Sac spiders hunt at night, feeding chiefly on small insects, and hide during the day in a silken tube or sac, from which they take their name.

They do not construct webs. Outdoors, they usually roll up leaves into a tube or may construct a retreat under stones.

Inside buildings, sac spiders are found in retreats in a variety of places including high up on walls near ceilings.

Fishing spiders are typically seen near ponds, swamps, or slow-moving streams, but some may be found at considerable distances from water.

Fishing spiders are the largest spiders in the Upper Midwest (1-inch long). With legs spread out, some fishing spiders cover as much as 4 inches.

They are generally dark-colored, usually brownish or grayish, with white markings.

Fishing spiders can “skate” across water and can dive underneath to capture prey.

They also can catch tadpoles, small fish and other small vertebrate animals.

Sowbug spider, also known as the woodlouse hunter or the dysderid spider, is an introduced species that is now common in the United States.

This medium-sized spider has distinctive coloration: the cephalothorax is purplish-brown, the abdomen is grayish-white, and the legs are orange.

Unlike the majority of spiders, the dysderid spider has only 6 eyes.

The fangs are quite large and project forward.

They wander at night in search of food and are ground-dwellers commonly found under rocks and debris.

Their preferred prey are sowbugs and pillbugs.

Jumping spiders are compact, medium-sized spiders that leap on their prey, often jumping many times their own body length.

They are active during the day and are often found on windows, ceilings, walls, and other areas exposed to sunlight. They are about 1/4- to 1/2-inch long and dark-colored with white markings.

Some can be brightly colored, including some with iridescent mouthparts.

These spiders move quickly in jerky, irregular motions and can run sideways and backward.

Jumping spiders have the best vision of spiders (have large middle eyes), seeing objects up to eight inches away.

Parson spider is a medium-sized spider (1/2-inch long) with a brownish body and gray abdomen with a white band running down over half the length of its abdomen.

Parson spiders move quickly. They actively hunt at night and chase their prey.

During the day, they are found outdoors under stones or loose bark.

Indoors, they hide under objects or in cracks or crevices.

They have been known to bite if trapped inside clothing or bedding. The bite can be painful and may cause allergic reactions in some people.

Crab spiders are small to medium-sized spiders (1/10- to 2/5-inch long) ranging in color from yellow or red to brown or gray.

The first four legs are longer than the back four and are held out to the sides giving a crab-like appearance. They can walk forward, sideways, or backward.

They are passive hunters they wait motionless and feed on insects that pass by closely.

Crab spiders are often found outdoors on flowers, stems or leaves.

They are rarely found indoors.

How to deal with spiders at home and outdoors

What to do with spiders in and around your home

Control of spiders is best achieved with an integrated approach that includes different non-chemical methods and occasionally insecticides. The type of spider can influence how you control it so it is important to identify the spider that is found.

Remember that spiders are not harmful so tolerate spiders when possible. When just small numbers are found, the easiest control is to capture and remove them.

Elimination of all spiders from a home is difficult and unnecessary. Properties located in areas where insects are numerous, such as by rivers, lakes, or fields, are more likely to have large numbers of spiders.

Each situation is unique, but the following guidelines describe the integrated techniques that can be used to control spiders.

  • Eliminate insects that serve as a food supply. Check in and under webs to see what insects have been captured.
  • Capture and remove individual spiders that have wandered inside.
  • Remove papers, boxes, bags and other clutter to reduce the number of good sites for spiders.
  • Remove webbing with a broom or vacuum and destroy any egg sacs that are found. Look especially around windows, in corners and in quiet places.
  • Sticky traps (small glue boards or cockroach traps) can be used to check for presence of spiders. Place traps along walls, under furniture and appliances and in other undisturbed locations.
  • Osage oranges (hedgeballs or hedge apples) are not effective and their use is not recommended.

Using pesticides

If you have a very large infestation of spiders and cannot control them otherwise, you can apply insecticide to cracks, gaps and other places where spiders may hide. Surface treatments and fogs are not effective.

Most insecticides labeled for ants and cockroaches are also labeled for spiders.

These products are commonly found in ready-to-use aerosol and liquid forms.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Dealing with spiders outdoors

Spiders are beneficial and an important component of the ecosystem. Getting rid of spiders in the lawn, landscape and garden is not recommended.

Use the following methods to prevent wandering spiders from getting inside your home:

  • Remove piles of bricks, firewood and other debris that may serve as homes for spiders.
  • Keep grassy or weedy areas near buildings cut short.
  • Trim back shrubs and other plants that directly contact your home.
  • Remove webs with a broom, vacuum or a hard spray of water.
  • Remove and destroy any egg sacs that are found.
  • Replace screens that fit poorly or are damaged.
  • Reduce outside lighting to control insects that encourage spiders.
  • Try to install yellow lights (less attractive to insects) instead of mercury or sodium vapor lights.
  • Place security lights on a pole shining toward a door rather than on the building above the door. This will reduce attracting insects.
  • Caulk or seal cracks or gaps around the foundation, doors and ground level windows.

Using pesticides

You may lightly apply a broad-spectrum insecticide on the outside of your home to reduce invasion by wandering spiders. Spray under siding, in cracks and crevices, and other places where spiders may hide. Make sure the insecticide is labeled for use on the exterior of buildings.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.


UC Davis Professors Ask Public to Help Name New Spider Species

An unnamed spider species lurks in the sand dunes of Monterey County's Moss Landing State Beach and UC Davis scientists need your help naming it.

UC Davis Professor of Entomology and Nematology Jason Bond recently appeared on Assistant Professor of Teaching Joel Ledford’s Tree of Life-UC Davis YouTube channel to discuss the discovery of this new, unique species of trapdoor spider and the upcoming paper describing it.

“It is remarkable in that it occurs in a relatively narrow section of sand dunes and has no geographically close relative,” said Ledford, who is a co-author on the upcoming paper and is formally trained in spider taxonomy. “It is being placed in a new genus (Cryptocteniza), but we would like input on the specific epithet.”

Bond and Ledford are asking the public to help name the species. So Cryptocteniza ________? The blank is where your creativity comes in. The Cryptocteniza part of the name is partly derived from the spider’s “hidden nature.”

Bond discovered the unnamed trapdoor spider species in 1997 during a field expedition to Moss Landing State Beach, an area he frequented to study California trapdoor spiders (Bothriocyrtum califonicum). Trapdoor spiders are sneaky predators. They burrow underground and cover themselves with a “trapdoor” constructed from environmental materials (like sand) and silk. When prey pass by, the trapdoor spider bursts forth, snaring the unsuspecting creature and dragging it into its subterranean lair.

While digging up trapdoor spiders, Bond found a specimen unlike anything he’d seen before.

“I immediately sort of thought to myself that it looked like a new genus of trapdoor spider,” he said during his interview with Ledford.

Bond collected female specimens, but in order to complete the picture of a new species, he needed male specimens. What followed was 22 years of unsuccessful searching. But science is an endeavor of patience.

In fall 2018, a photograph of a male trapdoor spider (the species unidentifiable) was posted to the app iNaturalist. Outfitted with geographic coordinates, Bond and his team worked with California State Parks to set up traps to capture the spiders. In September 2019, they finally collected a male specimen.

“It’s really unusual to discover a new species, a new genus, in the field,” Bond told Ledford. “Those sorts of discoveries today are usually from specimens that are found in museum collections.”

According to Bond, specimens of new species can sit on shelves of museum collections for decades before a taxonomist comes along and describes it.

Bond is no stranger to naming new species. He’s named spiders after Star Wars’ characters (Aptostichus sarlacc) and even named one after talk show host and comedian Stephen Colbert (Aptostichus stephencolberti).

I was thinking it’d be a nice idea to sort of ask the public to…give us some ideas about who or what they might like to name this species,” said Bond.

Those interested in helping name the species should add their suggestions to the comments section of the YouTube video. Bond and Ledford will select the best name from the list of suggestions.


5.3: Level 1: Sorting and Classifying a Spider Collection and Assessing its Comprehensiveness

  • Contributed by Nora Bynum
  • Instructor and Vice Provost for Duke Kunshan University (Environmental Science & Policy Division) at Duke University

Obtain a paper copy of the spider collection for forest patch "1." The spiders were captured by a biologist traveling along transects through the patch and striking a random series of 100 tree branches. All spiders dislodged that fell onto an outstretched sheet were collected and preserved in alcohol. They have since been spread out on a tray for you to examine. The spider collection is hypothetical but the species pictured are actual spiders that occur in central Africa (illustrations used are from Berland 1955).

The next task is for you to sort and identify the spiders. To do this you have to identify all the specimens in the collection. To classify the spiders look for external characters that all members of a particular group of spiders have in common but that are not shared by other groups of spiders. For example, leg length, hairiness, relative size of body segments, or abdomen patterning and abdomen shape all might be useful characters. Look for groups of morphologically indistinguishable spiders, and describe briefly the set of characters unique to each group. These operational taxonomic units that you define will be considered separate species. To assist you in classifying these organisms, a diagram of key external morphological characters of beetles is provided (Figure(PageIndex<1>)). Note that most spider identification depends on close examination of spider genitalia. For this exercise, however, we will be examining gross external characteristics of morphologically dissimilar species.

Figure(PageIndex<1>) Basic external characteristics of spiders useful for identifying individuals to species.

Assign each species a working name, preferably something descriptive. For example, you might call a particular species "spotted abdomen, very hairy" or "short legs, spiky abdomen" Just remember that the more useful names will be those that signify to you something unique about the species. Construct a table listing each species, its distinguishing characteristics, the name you have applied to it, and the number of occurrences of the species in the collection (Figure(PageIndex<2>)).

Figure(PageIndex<2>)

Last, ask whether this collection adequately represents the true diversity of spiders in the forest patch at the time of collection. Were most of the species present sampled or were many likely missed? This is always an important question to ask to ensure that the sample was adequate and hence can be legitimately contrasted among sites to, for example, assign areas as low versus high diversity sites.

To do this you will perform a simple but informative analysis that is standard practice for conservation biologists who do biodiversity surveys. This analysis involves constructing a so-called collector's curve (Colwell and Coddington 1994). These plot the cumulative number of species observed (y-axis) against the cumulative number of individuals classified (x-axis). The collector's curve is an increasing function with a slope that will decrease as more individuals are classified and as fewer species remain to be identified (Figure(PageIndex<3>)). If sampling stops while the collector's curve is still rapidly increasing, sampling is incomplete and many species likely remain undetected. Alternatively, if the slope of the collector's curve reaches zero (flattens out), sampling is likely more than adequate as few to no new species remain undetected.

Figure(PageIndex<3>) An example of a collectors curve. Cumulative sample size represents the number of individuals classified. The cumulative number of taxa sampled refers to the number of new species detected.

To construct the collector's curve for this spider collection, choose a specimen within the collection at random. This will be your first data point, such that (X=1) and (Y=1) because after examining the first individual you have also identified one new species! Next move consistently in any direction to a new specimen and record whether it is a member of a new species. In this next step, (X=2), but (Y) may remain as 1 if the next individual is not of a new species or it may change to 2 if the individual represents a new species different from individual 1. Repeat this process until you have proceeded through all 50 specimens and construct the collector's curve from the data obtained (just plot (Y) versus (X)). Does the curve flatten out? If so, after how many individual spiders have been collected? If not, is the curve still increasing? What can you conclude from the shape of your collector's curve as to whether the sample of spiders is an adequate characterization of spider diversity at the site?


SPIDERS

GENERAL INFORMATION AND BIOLOGY

Few creatures are as feared and misunderstood as spiders. For the most part, spiders are harmless and generally beneficial by keeping the insect populations in check. Spiders are seldom aggressive and bite only when threatened or injured. Few spiders bite people and the venom of most is harmless. However, the bite of the hobo spider, black widow and the brown recluse (also known as the Recluse or Fiddle Back) can be quite dangerous. Beneficial or not, if spiders become a pest you need to go to our SPIDER ELIMINATION section, where you will find pesticide (such as Suspend SC) and non-chemical control methods. Most infestations require both methods. And remember, the better you understand any pest, the easier it will be to eliminate or control.

Spiders are the largest group of arachnids. There are more than 35,000 named species worldwide, including about 3,000 in North America, but probably most spider species are still awaiting identification. When someone brings a spider to us for identification, it is usually large (which makes one believe it might be a Tarantula) or is marked with brilliant colors (which many believe might be a black widow), but most spiders that we are asked to identify are harmless.

These predators live almost everywhere - on the ground, under rocks, inside and underneath playground equipment, among grasses, on plants, in tree branches, in underground caves and even on the water. Spiders frequently stray into dwellings or other indoor habitats, or may be accidentally introduced on firewood, laundry that has been hung out to dry, and on flowers. Spiders will also sneak into our homes in boxes, clothing or furniture. In windows and near outdoor lighting, web-building spiders often construct webs because insect prey may be attracted at night by the lights and by air currents.

Spiders are easily recognized by the 4 pairs of seven segmented legs and (like all arachnids) have a cephalothorax and abdomen. But unlike scorpions, mites and daddy-long-legs, the cephalothorax and abdomen of the spider are separated by a visible waist or pedicel. The top of the cephalothorax is protected by a shield-like covering called the carapace.

Most species have 8 simple eyes, although some have less and a few species have none. Often the number and arrangement of eyes are important in identifying the different families. Below the eyes are 2 small jaws (or chelicerae) that end in fangs. Venom is produced in glands and empties through a duct in the fangs. This venom is used to paralyze or kill prey. Then the spider crushes the victim by rubbing the chelicerae against each other and against the enlarged bases of the pedipalps, located before the first legs. There are usually 6 finger-like silk glands (spinnerets) located beneath the abdomen, just in front of the anus.

Not all spiders spin webs. Some live in burrows, which they line with silk, while others have no retreat at all. All young spiders and some adult males release long silken strands, which they use like a parachute to ride the wind to other areas. This process is called ballooning. For more information about webs and silk production, read spider web article.

Most spiders lay their eggs in silken egg sacs that are placed in the web, attached to leaves or twigs, or carried around by the spider until the eggs hatch. Spiderlings (as the young are sometimes called) resemble adults and are often cannibalistic. All spiders are predators and most feed on insects, although a few large species prey on small vertebrate animals.


What species is this large-ish spider? - Biology

of Orange County, California
and nearby places

Photographed and compiled by Peter J. Bryant ([email protected]) Department of Developmental and Cell Biology,
University of California, Irvine, CA 92717, Ron Hemberger and Lenny Vincent.
Yellow background, exotic to California and/or North America.
See also World Spider Catalog and Conspicuous Spiders of Orange County, California
Back to Arthropods of Orange County, California

Conspicuous Spiders of Orange County: Identification Guide, by Lenny Vincent
Common Names of Arachnids
The demystification of the toxicity of spiders by Ed Nieuwenhuys.
Spiders of Kaweah Oaks Preserve, by Irene Lindsey.
Spiders of the genus Habronattus in California and Baja California by Marshall Hedin, San Diego State University.
Biology 104, The Biology of Insects and Spiders" taught by Dr. Lenny Vincent at Fullerton College.
Brown Recluse Spider (genus Loxosceles, Family Sicariidae) not included at this site because it is not reported from Orange County.


Monday, 18 June 2007

Evolution - Why are there exactly four nucleobases in DNA?

Here is a possible answer given by this paper:

It gives a Darwinian explanation to the question. It approaches the problem from Claude Shannon's theory for communication. It treats DNA replication conceptually and mathematically the same as a data transmission. It concludes that the system of four bases, not two, not six, replicates the most genetic information at the shortest amount of time.

The communicational analogy goes like this. If you have two data transmission systems, one can transmit, say, 1 MB per second, and the other can do 2 MB per second but cost less than twice as much. The answer is obvious you will buy the second service for a higher rate per cost. As a data service, it does not care what information you consume -- it can be spam, video, audio, etc. All that matters is the transmission rate. As for DNA replication, it is like a data transmission channel when one base is replicated a time along the mother DNA template. It too does not care whether the process is for a bacterium genome, or a plant, or an animal genome. The pay-off is in information and the cost is in time. Unlike your abiotic communication varieties, time is both the sender and the receiver of all messages of life, and different life forms or species are merely time's cell phones. So if one system can replicate more information in a unit time than another, the faster one will win the evolutionary arm race. A prey operating on a slow replicator system will not be able to compete with nor to adapt to a predator operating on a fast one.

Now because the A-T pair has only two weak hydrogen bonds but the C-G pair has three, A and T take a shorter time to complete duplication than the C and G do. Although the replication time is short in some fraction of nano second, but the time adds up quickly for genomes with base pairs in the billions. So having the C-G pair may slow down the replication, but the gain is in information. One base pair gives you 1 bit per base information. Two pairs gives you 2 bits per base information. But, having more base pairs may eventually run into a diminished return in information replication rate if the new bases take too long a time to replicate. Hence the consideration for the optimal rate of replication measured in information bits per base per time. Without information there would be no diversity, no complexity. Without replication in information there would be no life.

Using a simple transmission/replication rate calculation by Shannon you can calculate the mean rate for the AT-system, the CG-system, the ATCG-system, and for some hypothetical 6-bases, 2n-bases system whose new bases take progressively longer time to replicate. The analysis shows the ATCG-system has the optimal replication rate if the CG bases take 1.65 to 3 times longer to replicate than the AT bases. That is, a base-2 system replicates its bases faster but does not carry more information to have a higher bit rate. Likewise, a base-6 system has a greater per-base information but replicate slower on average to end up with a suboptimal bit rate.

According to a comparison from the paper, the base-4 system is about 40% faster than the A–T only system, and 133% faster than the G–C only system. Assume life on Earth started about 4 billion years ago, then the A-T only system would set back evolution by 1 billion years, the G–C system would do so by 2.3 billion years. For a hypothetical base-6 system, it would do so by 80 million years. In other words, life is where it should be because the base-4 system is able to transmit information through the time bottleneck at the optimal bit rate.

In conclusion, life is to replicate the most information with the shortest time, and the base-4 system does it the best. If ever there were other systems they would have lost the informatic competition to the base-4 system from the get-go. Darwin's principle works at life's most basic and most important level.

There are other explanations, all non-Darwinian. Most are based on the base's molecular structures. But these types of explanation border on circular argument -- using observations to explain themselves. They also face this catch-22 problem since there is no way to exhaust all possible bases for replication. However, such lines of exploration are fruitful regardless because more knowledge the better. But without taking information and its replication into consideration it is hard to imagine a sensible answer to the question.