Bug o’the Week – Wooly Bear Caterpillar again

Bug o’the Week
by Kate Redmond

Wooly Bear Caterpillar again

Greetings, BugFans,

The BugLady has been doing a little dance as she walks down the trail lately, trying to avoid stepping on wooly bear caterpillars (her mission statement, after all, is “Less stepping on bugs”).  She has been less successful when she drives.  So, it’s time to rerun this episode that originally aired in 2009, but that she re-posts every five years or so.  A few new words; some new pictures:

Wooly bear caterpillars are tiger moths in the family Erebidae and in the subfamily Arctiinae.  It’s a diverse family that includes almost a thousand species of tiger, underwing, Zale, tussock moths, and more, in North America, and many more worldwide (except Antarctica).  If you have an older insect guide, tiger moths are in the family Arctiidae, but everything that was once in Arctiidae has been folded into Arctiinae.  Tiger moths are unusual in that they have an organ on their thorax that vibrates to produce ultrasonic sound.  They “vocalize” to attract mates and to defend against predators.  If you have sound-making ability, you also need “ears,” and those are on the thorax, too.  Like tigers, the adults of many species are hairy and sport bold color patches, stripes or patterns. 

Many tiger moth caterpillars are fuzzy, earning a group name of wooly bears or wooly worms (two “lls” or one “l” – take your pick.  Two lls is more common in Britain and one l is more common here).  The wooly bear du jour is the ultra-familiar rust-and-black-banded caterpillar whose grown-up name is Isabella Tiger Moth (Pyrrharctia isabellahttps://bugguide.net/node/view/1937881/bgimage.  The caterpillar goes by the generic Wooly Bear, and also Black-ended Bear, and the Banded Wooly Bear.  Pyrrharctia is a “monotypic genus” – there’s only this single species in it, and they’re only found in North America. There is an amazing amount of information out there about wooly bear caterpillars, and much of it is contradictory, a problem that is exacerbated by the fact that there are many different kinds of caterpillars that are called wooly bears. 

A mature female Isabella Tiger Moth “calls” to males by emitting pheromones (chemical signals) at night, and the males zero in on her by using their sensory antennae.  Isabella Tiger Moths lay their eggs on a wide variety of plants during the warm months.  While some caterpillars are known for their picky eating, wooly bears are generalists.  They feed during the day, munching on handy, low-growing plants like grasses, “weeds” and wildflowers (cannibalism has also been reported).  Their catholic eating habits ensure that they’re constantly surrounded by food during their autumnal wandering in search of wintering sites.  

Wooly bears spend the winter as caterpillars, out of the weather under tree bark or debris, or in your garage.  Do they become “bug-cicles”?  Yes, indeed – they’ve even been found frozen in a chunk of ice.  But, like other organisms that are dormant in the dead of winter, wooly bears produce a chemical called a cryoprotectant (antifreeze) that protects living tissue against damage from freezing and thawing.  Wooly bears will stir and walk around on mild winter days and then go back into hiding when the temperatures drop again.  They wake up with the warm weather, resume eating, and pupate in late spring in a fuzzy cocoon into which they incorporate their own “setae” (hairs) https://bugguide.net/node/view/2249302/bgimage.  According to Wikipedia, Arctic summers are so short that wooly bears may need to live through several of them to become mature enough to pupate.   

One area of disagreement among references is whether the wooly bears’ wool/setae/hairs/bristles are irritants.  Having a bristly covering discourages some predators, although in the Fieldbook of Natural History, E. L. Palmer says that “skunks and a few other animals roll hairs off the caterpillars before they eat them.”  Certainly, the stiff hairs make it a harder to pick a wooly bear up, and when you do pick one up and it inevitably curls into a defensive ball, it’s pretty slippery.  Some sources say that the wooly bears’ setae contain a stinging/irritating/venomous chemical, and other sources specifically say they do not.  Still other references say the setae may cause dermatitis mechanically – that they might break off in your skin (like one of those wretched, furry cacti); and others say that that unlike many hairy caterpillars, wooly bears are harmless.  The BugLady has never suffered any ill effects from handling the familiar, rust-and-black wooly bears.

Wooly bears have been famous since Colonial times for two things: 1) their habit of crossing the roads in fall (the BugLady wonders what they crossed before the Colonists arrived and started making roads); and 2) their alleged ability to predict the weather. 

The weather lore angle was initiated by those same, road-building Colonists, who needed some forecasting done in those pre-Weather Channel days so they could figure out when to plant and harvest crops.  If its rust-colored middle band is wide, says the Almanac, the winter will be a mild one; if there’s lots of black, batten down the hatches (except for a few sources that say the opposite – that lots of rust means lots of cold).

A surprising number of scientists have felt obligated to leap in and deflate the weather story.  To them the BugLady says “Lighten up, Party Poopers, and let a little fantasy into your lives.”  They tell us that the widening middle band is a result of age, and that each time wooly bears molt, a black band becomes a rust band (except for a few who say the opposite – that rust turns to black).  So, a rustier wooly bear is an older wooly bear.  The BugLady has been curious about why the early fall wooly bears seemed more pessimistic than the later fall wooly bears and is happy to have that one resolved.  In spring, a blacker wooly bear is one that became dormant prematurely, and may indeed be telling the weather – of the previous fall.  Other research suggests that a wooly bear with lots of rust lived in dry conditions, and one source says that a wooly bear with wide black bands grew up where the habitat was wetter.  Still other scientists say that there is considerable variation in color within newly-hatched individuals from a single clutch of eggs, and that the variation persists as they age.

We have Dr. Curran, a curator of insects at the American Museum of Natural History, to thank for popularizing the wooly bear.  Charmed by the old weather saying, Dr. Curran drove north from New York City along the Hudson to Bear Mountain State Park each year for eight years in the late 1940’s and early 1950’s to measure the coloration of the wooly bears he found there.  During those years, the rusty bands predicted mild winters.  He leaked the forecasts via a friend at a NYC newspaper, and the publicity his reports generated put wooly bears on the map.  But Dr. Curran’s only real hypothesis was that Scientists Just Want to Have Fun.  He and his friends enjoyed the scenery, the foliage and the wooly bears on their annual fall forays and formed “The Original Society of the Friends of the Woolly Bear.”  Thirty years after Dr. Curran’s outings ceased, the folks at Bear Mountain State Park resurrected the Friends organization and the wooly bear count.

Wooly bears are embraced by children and adults alike, and Annual Wooly Bear Festivals are celebrated:

Clearly, Wisconsin is missing the boat, here (though Milwaukee had a third annual Wooly Bear Fest in January of 2015). 

Go outside – chart wooly bears. 

Kate Redmond, The BugLady

Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/

Bug o’the Week – Bugs in the News XIV

Bug o’the Week
by Kate Redmond

Bugs in the News XIV

Greetings, BugFans,

Time to chip away at the BugLady’s giant collection of insect articles.  Note that most of them are from various (free) on-line reports put out by the Smithsonian.

 

SPIDERS – We have semi-aquatic spiders around here, too.  Most, like the Six-spotted fishing spider are in the nursery web spider family – https://www.smithsonianmag.com/science-nature/these-funky-spiders-live-near-or-in-water-180984283/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&spMailingID=49766545&spUserID=ODg4Mzc3MzY0MTUyS0&spJobID=2701966506&spReportId=MjcwMTk2NjUwNgS2.  

TOOL-USING SPIDERS – Scientists get all excited when a new tool-using behavior is discovered in a mammal or bird.  Invertebrates use tools, too, like wasps that use small sticks to help excavate nest tunnels in soil, tree crickets that take advantage of curved leaves to amplify their calls, ants that soak up liquids with bits of absorbent materials to make it easier to carry the liquids back to their nests, and some beetle larvae that build a fecal shield for protection.  There’s been a good deal of discussion among scientists about what constitutes a “tool,” and some (but not all) of those definitions have included the use of other organisms.  Here’s a spider that uses a firefly: https://www.smithsonianmag.com/smart-news/these-spiders-use-captured-fireflies-as-flashing-lures-to-snare-more-prey-180984940/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&spMailingID=50099331&spUserID=ODg4Mzc3MzY0MTUyS0&spJobID=2762283843&spReportId=Mjc2MjI4Mzg0MwS2.     

ALIEN HORNETS – Not much in the news this year about the Asian murder/Northern giant hornet – the folks in the Pacific Northwest are cautiously optimistic that they’ve found all the nests.  Just when you thought it was safe to get back into the water (metaphorically speaking), along comes the Yellow-legged hornet, on the opposite coast: https://extension.psu.edu/yellow-legged-hornet

ENTOMOPHAGY (the art and science of eating insects) is gaining in popularity here, but it’s traditionally been a feature of other cuisines.  Singapore approved 16 insect species for food — https://www.smithsonianmag.com/smart-news/singapore-approves-16-insect-species-as-food-180984685/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&spMailingID=49962829&spUserID=ODg4Mzc3MzY0MTUyS0&spJobID=2741185369&spReportId=Mjc0MTE4NTM2OQS2

BUZZING BUTTERFLIES – bumble bees are famous for “buzz pollination” – causing flowers to release their protein-rich pollen by grabbing the flower parts that produce pollen (anthers) with their mandibles, disengaging their flight muscles, and vibrating their thoracic muscles mightily.  The result is not flight, but movement/shaking of the pollen-holding structures that causes pollen to rain down onto the bee.  They are aided in this by the electric charges that build up on their bodies as they fly and that attract pollen.  Can butterflies do this?  https://www.smithsonianmag.com/smart-news/static-electricity-may-help-butterflies-and-moths-pick-up-pollen-180984823/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&spMailingID=50039609&spUserID=ODg4Mzc3MzY0MTUyS0&spJobID=2760223063&spReportId=Mjc2MDIyMzA2MwS2

ANTS – Some ants produce their own pharmaceuticals:  https://www.smithsonianmag.com/smart-news/honey-made-by-ants-could-protect-against-bacteria-and-fungi-180982611/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&spMailingID=48539902&spUserID=ODg4Mzc3MzY0MTUyS0&spJobID=2503571888&spReportId=MjUwMzU3MTg4OAS2

CLIMATE CHANGE – WHAT COULD POSSIBLY GO WRONG? – https://www.smithsonianmag.com/smart-news/rash-causing-moths-are-spreading-because-of-climate-change-180979650/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=20220228-daily-responsive&spMailingID=46470006&spUserID=ODg4Mzc3MzY0MTUyS0&spJobID=2200009908&spReportId=MjIwMDAwOTkwOAS2.

UP CLOSE AND PERSONAL – As seasoned BugFans know, the BugLady is a big fan of macro/extreme macro/scanning electron microscope (SEM) photography.  Enjoy:  https://www.smithsonianmag.com/science-nature/these-stunning-portraits-of-insects-reveal-the-intricacies-of-an-amazing-world-180984926/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&spMailingID=50122698&spUserID=ODg4Mzc3MzY0MTUyS0&spJobID=2763062134&spReportId=Mjc2MzA2MjEzNAS2

Kate Redmond, The BugLady

Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/

Bug o’the Week – Speed-dating the Spiders – Black Widows
by Kate Redmond

Bug o’the Week

Speed-dating the Spiders – Black Widows

Howdy, BugFans,

For years, BugFan Tom has sent pictures from the Deep South of Black widow spiders that he encounters while conducting research in southern thickets in the dead of night.  Thanks for the pictures, Tom.

The first thing you should know about Black widows is that they need better PR.  Widow spiders are so-named because the female (allegedly) eats the male after mating.  It’s called “sexual cannibalism,” and the protein meal is supposed to boost the chances of successful egg-laying.  But, this is a behavior that was first observed in the lab, where the male had few escape options, and it’s suspected that it happens far less frequently in the wild (similar laboratory observations have given the Praying mantis an equally bad rap).  Courtship is a tricky business for male spiders, and sexual cannibalism is known from other groups of spiders besides the widows.

Widow spiders are in the Cobweb/Tangleweb spider family Theridae and in the genus Latrodectus, the widows/true widows (Latrodectus means “biting in secret”).  There are about 35 species worldwide, with 5 in North America (the Northern, the Southern, and the Western, all called “black widows,” plus the Red widow, and the non-native Brown widow).  As their names suggest, they’re distributed across the continent https://bugguide.net/node/view/1999/data.  Climate change is helping them move north.

They are considered to be fairly common spiders, but they stay out of sight in dark areas under rocks, in woodpiles, in crevices and holes, tree stumps, in outbuildings, animal burrows, unused grills, etc. – usually near the ground.  They are not generally an indoor spider but will come in out of the cold.

Latrodectus spiders are the largest spiders in their family – females are about a half-inch long (an inch and a half, including legs), and males are about half that size https://bugguide.net/node/view/34659/bgimage.  Widow spiders are famous for the red, hourglass-shaped markings on the underside of the female’s abdomen, but the hourglass may be incomplete, split, or even absent.  Males have a variety of spots along the midline, and immatures are pale before they morph into male coloration and then into their adult patterns.  They are also called “comb-footed” spiders because their feet are covered with bristles that they use to handle the silk when they’re wrapping their prey. 

Instead of a tidy, platter-shaped orb-web, widows spin a strong, messy, sticky, three-dimensional web https://bugguide.net/node/view/1130899 with a dense retreat at one side where the spider hides in the daytime.  A hungry spider will build a stickier web, and a satiated spider a web with more internal structure.  Widows eat a variety of invertebrates (size seems to be no object https://bugguide.net/node/view/109318/bgimage), including other spiders; they have a taste for red fire ants, and they may even eat small vertebrates that get stuck in their web.  They inject a venom to subdue their prey (more about that in a sec), and then an enzyme to liquefy it.  

Widows are targeted by several species of solitary wasps that use them to provision their egg chambers, and they’re also eaten by scorpions, centipedes, and mantises.  Their red markings warn birds that taking on a widow would be a bad idea, though their toxins are harmless when ingested.

Males wander the landscape in search of females, and females stick pretty close to their webs.  When he finds a female, he plucks the strands of her web to ascertain that she is the same species and to introduce himself, and he shakes his abdomen to produce vibrations.  He may sever portions of her web to cut off her potential escape routes (alternatively, some researchers think that the portions of her web that he cuts and bundles up are the pheromone-laden bits, so he’s making her web less noticeable to other males).  Even then, he advances with caution, informed by chemicals in the web that tell him whether she is well fed (and therefore approachable) or hungry. 

Females make egg sacs that contain about 250 eggs https://bugguide.net/node/view/2213427/bgimage, and they can produce as many as nine sacs per summer (she has a much longer lifespan than he does).  The eggs within the sac, which is suspended in her web and guarded by Mom, hatch in three to four weeks, but sibling cannibalism is rampant immediately after the spiderlings emerge, and even though they balloon away quickly, only a small fraction survive.

Two species of Black widow, the Southern and the Northern, inhabit the eastern half of the continent, and because of their overlapping ranges and similar habits, a lot of publications lump them together. 

SOUTHERN BLACK WIDOWS or Hourglass spiders (Latrodectus mactans) are found as far north as Illinois and New York State and even southern Canada https://bugguide.net/node/view/26336/data.  Shiny black, with a full hourglass pattern – two joined, red triangles with the rear triangle wider than the front one – they’re considered the “classic” Black widow https://bugguide.net/node/view/2035680/bgimage.  They also have red markings on the top of the abdomen https://bugguide.net/node/view/731853/bgimage.  Males have some spots on their abdomens https://bugguide.net/node/view/710792/bgimage.   

Southern black widows are declining in the South, and the likely suspect is the non-native (from Africa) Brown widow spider (Latrodectus geometricus).  In lab situations, when Brown widows were offered an array of other spiders to eat, their top pick was Southern black widows.  Brown widows also have a higher reproductive rate and more potent venom than native widows, though they inject a smaller amount of it, and they are less likely to bite.  

NORTHERN BLACK WIDOW – Yes, Black widows are native to God’s Country, though they’ve rarely seen.  They’ve been recorded in fewer than 10 counties, mostly near Lake Michigan, with its more moderate climate.  The same species is at home in the South and was photographed there by BugFan Tom.  Northern black widows (Latrodectus variolus) are found over the eastern half of the continent from Texas to Ontario, and they’re more common in the northern parts of their range https://bugguide.net/node/view/26421/data

In this species, the signature hourglass markings are likely to be interrupted, with a gap between the top and bottom trapezoid, or with one side larger or absent, and there’s a row of red spots on the top side of the abdomen.  Males have four pale bands on each side of the abdomen.  The Northern black widow is slightly smaller than its southern cousin, and slightly less venomous. 

ABOUT THAT BITE

Widows seldom bite people (about 2500 reports a year) – they would rather flee or play dead than fight, and most bites occur when people poke their hands into dark places or when a spider gets squished against a person.  While they are not the most toxic spider on earth, the venom of a female widow spider (males and immatures are harmless) is 15 times more toxic than that of a rattlesnake.  They don’t inject very much venom per bite, but even that small amount will get your attention.  Their venom contains a neurotoxin called latrotoxin (named for the genus) that rarely causes death but does cause a syndrome called Latrodectism, whose symptoms include some muscle paralysis, intense pain and abdominal cramping, tachycardia, and other unpleasantness that may last for three to five (or more) days.  It’s recommended that people who get bitten, especially children, the elderly, and the pregnant, call their doctor or hospital – there’s an antivenom.  

Says Wikipedia – “In 1933, a University of Alabama medical faculty, Allan Blair conducted an experiment on himself to document the symptoms of a black widow bite, and to test whether someone can build immunity after being bitten15 -. The effects of the bite were so painful and harsh that Blair failed to complete the experiment and did not follow through with being bitten a second time.”  

[Esoteric Fact of the Day: (because the BugLady’s youngest child once called her an “esoterrorist”) the old (1800’s) terms were venin and antivenin, but in 1981, the World Health Organization standardized venom and antivenom as the preferred terms in the English-speaking world.]

As always, mind where you stick your fingers and toes. 

Kate Redmond, The BugLady

Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/

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