Spider Silk

Orb Spider Web
Contains 3 Types of Silk

Courtesy & Copyright 2011
Terry Greene, Photographer

Spider silk has long been of interest to scientists and engineers for its incredible strength. Silk can be, by weight, a stronger fiber than steel or Kevlar. But new research has discovered that the strength of the individual fibers does not explain the durability of a web, which can remain functional after sustaining extreme stress. The web’s overall design adds to silk’s durability to create a truly functional product.

Spiders utilize silk for many different reasons – transportation, lining burrows, protecting and securing egg cases, and of course for catching prey. Amazingly, an individual spider has the ability to manufacture several different types of silk, which are used for different purposes. In a typical orb-style web there are at least three kinds of silk at work. One is strong and dry, making up the ‘spokes’ of the web. These are the strands upon which the spider itself moves around, so as not to get stuck in its own trap. The strands which create the characteristic spiral pattern are actually made of two types of silk – one is a fine, stretchy fiber, and the other a sticky, glue-like substance. Together, these two silks make up the part of the web responsible for snaring prey.

Another important property of silk is that when stretched the fiber stiffens. As more pressure is applied, the properties of the silk change, allowing it to become stretchy and flexible. If still more pressure is added, the silk stiffens again, until finally it breaks. Originally, this stiff-stretchy-stiff response to stress was viewed as a weakness, but when analyzed as part of an interconnected web, that’s not the case. A team of scientists from MIT noted that webs could be subjected to a lot of force with only minimal damage. Whether the force was localized – for example while ensnaring a large insect – or more widespread over the entire surface – such as pressure from strong winds – the damage incurred by the web was minimal. Only the individual strands that endure the most pressure break, while others stiffen, flex, and remain intact.

Localized damage allows the spider to more often than not simply repair a web instead of abandoning it and starting over. Creating silk and weaving a web is a costly process for a spider – it takes up a lot of the arachnid’s energy. The ability to simply patch the broken parts is a more efficient strategy which requires less energy expenditure and fewer materials than weaving a new web.

Figuring out how to mimic this response to stress on a material could be infinitely useful in the human world. Imagine a skyscraper in an earthquake that fails in one small place where the forces are strongest – not in its entirety as is currently the case. That same earthquake-damaged building might also need only minimal repairs, saving time, money, and materials. Oh the lessons we could learn from one of nature’s smallest creatures…

Thank you to the Rocky Mountain Power Foundation for supporting the research and development of this Wild About Utah topic. For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Credits:
Images: Courtesy & Copyright 2011 Terry Greene
Text:     Andrea Liberatore, Stokes Nature Center in Logan Canyon.

Additional Reading:

Chandler, David L. (2012) How Spider Webs Achieve Their Strength. MIT News Office. Available online at: http://web.mit.edu/newsoffice/2012/spider-web-strength-0202.html

National Science Foundation press release (2012) A Spider Web’s Strength Lies in More Than its Silk. Available online at: http://www.nsf.gov/news/news_summ.jsp?cntn_id=123041

Law, Steven (2012) Curious Things About Spider Webs. Available online at: http://www.ksl.com/?nid=968&sid=20488145

Insect Mimicry and Camouflage

American Hoverfly, Courtesy National Park Service, nps.gov/long/naturescience/insects.htm
American Hoverfly
Courtesy National Park ServicePeach Tree Borer, Courtesy Cooperative Extension, Copyright 2009 Clemson UniversityPeach Tree Borer
Courtesy USDA Cooperative Extension
© 2009 Clemson University

Katydid, Courtesy Stokes Nature Center, Scott Biggs, Photographer Katydid
Courtesy Stokes Nature Center
Scott Biggs, Photographer

Monarch Butterfly, Courtesy Utah Division of Wildlife Resources, J. Kirk Gardner, Photographer Monarch Butterfly
Courtesy Utah Division of Wildlife Resources
J. Kirk Gardner, Photographer
Licensed Under CCL 3.0

Click for a closer view of a Tiger Swallowtail Butterfly, Courtesy Utah Division of Wildlife Resources, J. Kirk Gardner, Photographer Tiger Swallowtail Butterfly
Courtesy Utah Division of Wildlife Resources
J. Kirk Gardner, Photographer
Licensed Under CCL 3.0

 

Insects are the most diverse class of organisms on earth, with more than 900 thousand known species. With that many different kinds of bugs, it’s no wonder that they take on such a vast array of shapes, sizes, and colors. From Luna moths to fruit flies to millipedes, the diversity of this class of life is immense. Some insects have developed a shape and coloring so deliberate that it’s almost astounding. These insects are mimics – bred to look like something they aren’t, in an attempt to get a leg up on the survival game.

Insects can mimic all kind of things – stick bugs, for example, make such convincing twigs that you’ll never know they’re around until they move. Katydids look just like bright green leaves, and there are some species of caterpillar that in their youngest stages look just like splatters of bird droppings. But the mimics that I find most interesting are those who mimic other insects.

There are two main types of insect-to-insect mimicry. Batesian mimicry occurs when one harmless species mimics another dangerous one. Species that look like something fierce can capitalize on that insect’s dangerous reputation and potentially be safer from predators because of it. A common Utah pest, the peach tree borer, is a moth that very closely resembles a wasp in both its morphology and behavior. Harmless, nectar-eating hoverflies exhibit the black and yellow body stripes of a bee. Apparently, it’s not just humans who want to stay away from the business end of a wasp or a bee – many insect predators, too, give them a wide berth.

Ants also have a fierce reputation in the animal world, and so attract a lot of mimics. A number of spider species not only mimic ants in morphology and behavior, but some also give off ant pheromones, making them smell like friend rather than foe. While many ant-mimicking spiders go undercover as a way to hide from their own predators, some do use their disguise as a way to access the nest of their prey.

Batesian mimicry is a delicate balance. Predators need to catch a wasp or two before they associate that color pattern with dangerous prey. If there are too many tasty mimics around, the predators will stop associating black and yellow stripes with a dangerous object and the mimic’s ploy would fail to work.

A slight variation on Batesian mimicry are insects with false faces and false eyes. Tiger swallowtails – those large yellow and black butterflies – have red and blue spots on each of their hind wings at a place farthest from their body. These spots, combined with the skinny black ‘tails’ from which the species gets its common name, are meant to look like the eyes and antennae of another, possibly larger and more fierce, insect. This imagery is meant to frighten off predators, but also in the case of an attack, to spare the most important part of the butterfly’s body.

The second, less common, form of insect-to-insect mimicry is called Müllerian mimicry. This occurs when two equally distasteful insects come to resemble one another. Most of us are familiar with the monarch butterfly. As caterpillars, they feed exclusively on toxic milkweed. The caterpillars take the toxins into their bodies and retain them as adults, making them not only bad-tasting but also poisonous. Predators have learned to associate that distinct orange and black wing pattern with a bad experience, and therefore leave them alone. Viceroy butterflies look incredibly similar to monarchs – the only difference being an extra line of black on the hindwings of a viceroy. While once thought to be Batesian mimics, recent studies have shown that viceroys are equally unpalatable. Their similarity in looks to monarchs, then, serves to reinforce the distasteful nature of both species.

Mimicry is of course, not restricted to the insect kingdom. Some plants have gotten into the mimicry business in order to trick insects. The hammer orchid, which grows in Australia, has a flower that mimics a female bee. Male bees, in mistakenly trying to mate with the flower, collect pollen that they then carry with them to the next, ensuring pollination of this sneaky plant. So this ingenious tactic some insects use to gain a leg up in the game of survival can also be used against them to the advantage of others. Isn’t life amazing…

For more information and photos of some insect mimics, visit our website at www.wildaboututah.org. For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Many thanks to Don Viers for his input on this piece.

Credits:

Photos: Courtesy and copyright as marked

Text: Andrea Liberatore, Stokes Nature Center

Additional Reading:

Imes, Rick (1997) Incredible Bugs: The Ultimate Guide to the World of Insects. Barnes & Noble Books. New York, NY

Pyle, Robert Michael (1981) National Audubon Society: Field Guide to Butterflies, North America. Alfred A. Knopf. New York, NY

Viers, Don (2013) Personal conversations

Ritland, David B., Brower, Lincoln P. (1991) The Viceroy butterfly is not a Batesian mimic. Nature, vol. 350, 497-8. Available online at: http://www.nature.com/nature/journal/v350/n6318/abs/350497a0.html

Cushing, Paula E. (2012) Spider-ant associations: An Updated Review of Myrmecomorphy, Myrmecophily, and Myrmecophagy in Spiders. Psyche, vol. 2012. Available online at: http://www.hindawi.com/journals/psyche/2012/151989/

NRCS Partners with Farmers, Ranchers to Aid Monarch Butterflies, Posted by Jason Weller, Chief, Natural Resources Conservation Service, on November 12, 2015, USDA Blog, http://blogs.usda.gov/2015/11/12/nrcs-partners-with-farmers-ranchers-to-aid-monarch-butterflies/

Tick Tock

Tick Tock
Rocky Mountain wood tick
Dermacentor andersoni
Courtesy Mat Pound, USDA Agricultural Research Service, Bugwood.org

Hi I’m Holly Strand from the Quinney College of Natural Resources at Utah State University.

It’s springtime–bringing warm light-filled days, colorful blooms, chirping birds and bloodthirsty ticks. Ticks are arachnids like spiders and scorpions. They vary in size, shape, and color. But they all have barbed feeding tubes that they use to excavate a hole in your skin so they can bury their heads and suck your blood. Their accordion-like bodies expand as they sip and sip and sip.

Most ticks go through three life stages after hatching: six-legged larva, eight legged nymph and then adult. The ticks need a single blood meal during each of these life stages. To get this meal, ticks wait for their victims–usually a mammal–using a behavior called “questing.” Questing ticks crawl up the stems of grass or perch on the edges of leaves and extend their front legs–like a toddler signaling he wants to be picked up. The presence of carbon dioxide, or heat, or movement let the tick know that a meal may be passing by soon and the tick gets ready. When a passing animal brushes the tick’s extended legs, the tick simply climbs on board. It doesn’t jump. It just feels and attaches. Some ticks will bore in immediately and others will cruise around looking for a spot where the skin is thin and blood vessels closer to the surface.

This head-burying and blood-sucking behavior alone gives ticks an unsavory reputation. But of course ticks are also dangerous in that they transmit disease through their saliva. The Rocky Mountain wood tick and American dog tick have been found to feed on Utahns. Both can transmit Rocky Mountain spotted fever and tularemia, also known as rabbit fever.

The Western black-legged tick is another Utah native. It’s a vector for lyme disease. According to the Utah Dept of Public Health, it does appear that a small number of individuals may have acquired the disease in Utah. Human transmission from this tick has definitely occurred in California.

Ticks can be found in grasses, shrublands, forests—basically everywhere. Ticks in hotter, arid parts of the state reach peak activity in April and May while ticks at higher elevations are active from May through July. Ticks in all geographic areas are active in the fall as temperatures cool and moisture increases.

Now that I’ve frightened you, know that the chance of getting a tick born disease in Utah is still small. In spite of its name, the vast majority of Rocky Mountain spotted fever cases are reported in eastern and central states. And in any given year there will probably be less than 10 cases of each disease mentioned. And they are all treatable if caught early. So don’t let fear of ticks keep you inside. Just remember that they are out there and check for them when you’ve been brushing up against vegetation.

To remove a tick, do NOT burn it with a hot match or smother it in petroleum jelly. These methods can make a tick burrow deeper before dying. Instead, remove the tick as quickly as possible using the fine tipped tweezers that you carry in your first aid kit.

For more information including tips on tick avoidance and removal go to www.wildaboututah.org.

For Wild About Utah, I’m Holly Strand.

Credits:

Image: Courtesy Bugwood.org, licensed under Creative Commons Attribution 3.0 License.
Text: Holly Strand

Sources & Additional Reading

Centers for Disease Control and Prevention. Pages on Preventing Tick Bites; Life Cycle and Hard Ticks that Spread Disease
http://www.cdc.gov/ticks/avoid/on_people.html [Accessed March 19, 2014]

James, Angela M. 2006. Distribution, Seasonality, and Hosts of the Rocky Mountain Wood Tick in the United States. Journal of Medical Entomology 43(1):17.
http://www.researchgate.net/publication/7272126_Distribution_seasonality_and_hosts_of_the_Rocky_Mountain_wood_tick_in_the_United_States

McDade, J E and V F Newhouse. 1986. Natural History of Rickettsia Rickettsii
Annual Review of Microbiology. Vol. 40: 287-309
http://www.annualreviews.org/doi/abs/10.1146/annurev.mi.40.100186.001443

USU Extension. 2010. Ticks and Associated Diseases Occurring in Utah. Utah Pests News. Volume IV. Summer 2010.
http://utahpests.usu.edu/htm/utah-pests-news/summer2010&ticks

Utah Department of Health, Bureau of Epidemiology.
Fact sheets on Rocky Mountain spotted fever, tularemia and lyme disease.
http://health.utah.gov/epi/fact_sheets/Default.htm

Utah Department of Health, Bureau of Epidemiology.
Historical Communicable Disease Reports 1980 to present.
http://health.utah.gov/epi/100yr/100yr.html

Skerrett, Patrick. 2013. Matchless strategy for tick removal; 6 steps to avoid tick bites. Harvard Medical School Health Blog. Posted June 7, 2013.
http://www.health.harvard.edu/blog/matchless-strategy-for-tick-removal-6-steps-to-avoid-tick-bites-201306076360

Zimmer, Carl. 2013. Outside Magazine, June issue.
http://www.outsideonline.com/outdoor-adventure/science/feeding-frenzy.html

Spider Silk

Orb Spider Web
Contains 3 Types of Silk

Courtesy & Copyright 2011
Terry Greene, Photographer

Spider silk has long been of interest to scientists and engineers for its incredible strength. Silk can be, by weight, a stronger fiber than steel or Kevlar. But new research has discovered that the strength of the individual fibers does not explain the durability of a web, which can remain functional after sustaining extreme stress. The web’s overall design adds to silk’s durability to create a truly functional product.

Spiders utilize silk for many different reasons – transportation, lining burrows, protecting and securing egg cases, and of course for catching prey. Amazingly, an individual spider has the ability to manufacture several different types of silk, which are used for different purposes. In a typical orb-style web there are at least three kinds of silk at work. One is strong and dry, making up the ‘spokes’ of the web. These are the strands upon which the spider itself moves around, so as not to get stuck in its own trap. The strands which create the characteristic spiral pattern are actually made of two types of silk – one is a fine, stretchy fiber, and the other a sticky, glue-like substance. Together, these two silks make up the part of the web responsible for snaring prey.

Another important property of silk is that when stretched the fiber stiffens. As more pressure is applied, the properties of the silk change, allowing it to become stretchy and flexible. If still more pressure is added, the silk stiffens again, until finally it breaks. Originally, this stiff-stretchy-stiff response to stress was viewed as a weakness, but when analyzed as part of an interconnected web, that’s not the case. A team of scientists from MIT noted that webs could be subjected to a lot of force with only minimal damage. Whether the force was localized – for example while ensnaring a large insect – or more widespread over the entire surface – such as pressure from strong winds – the damage incurred by the web was minimal. Only the individual strands that endure the most pressure break, while others stiffen, flex, and remain intact.

Localized damage allows the spider to more often than not simply repair a web instead of abandoning it and starting over. Creating silk and weaving a web is a costly process for a spider – it takes up a lot of the arachnid’s energy. The ability to simply patch the broken parts is a more efficient strategy which requires less energy expenditure and fewer materials than weaving a new web.

Figuring out how to mimic this response to stress on a material could be infinitely useful in the human world. Imagine a skyscraper in an earthquake that fails in one small place where the forces are strongest – not in its entirety as is currently the case. That same earthquake-damaged building might also need only minimal repairs, saving time, money, and materials. Oh the lessons we could learn from one of nature’s smallest creatures…

Thank you to the Rocky Mountain Power Foundation for supporting the research and development of this Wild About Utah topic. For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Credits:
Images: Courtesy & Copyright 2011 Terry Greene
Text:     Andrea Liberatore, Stokes Nature Center in Logan Canyon.

Additional Reading:

Chandler, David L. (2012) How Spider Webs Achieve Their Strength. MIT News Office. Available online at: http://web.mit.edu/newsoffice/2012/spider-web-strength-0202.html

National Science Foundation press release (2012) A Spider Web’s Strength Lies in More Than its Silk. Available online at: http://www.nsf.gov/news/news_summ.jsp?cntn_id=123041

Law, Steven (2012) Curious Things About Spider Webs. Available online at: http://www.ksl.com/?nid=968&sid=20488145