Ant Talk

Apr 19 2011 Published by under Biology & Environment

Ant on a mustard flowerWhen a wood thrush flew by the Trailhead mound carrying a grasshopper to her own nest and dropped part of the crushed insect to the ground, a patrolling worker found it in less than a minute and triggered a chain action. The worker examined the grasshopper, tasted it briefly, then ran back to the nest entrance. On the way, she touched the tip of her abdomen repeatedly to the ground, laying down a thin trail of chemicals. Entering the nest, she rushed up to each nest mate she passed, brushing her face close to theirs. With their antennae, her nest mates detected both the trail substance and the smell of grasshopper. The signals now proclaimed, Food. I have found food. Follow my trail! Soon a mob of ants ran out, followed the trail, and gathered around the delicious grasshopper haunch.
~ From E.O. Wilson's "Trailhead"

When I think of ants it's with a mixture of fascination and loathing.

Loathing because of the seemingly constant battle required to keep them from taking up residence in my kitchen. It's not just the unpleasantness of having to remove all the contents of my cabinets to figure out how the ants are getting in.  It's the lingering sensation after handling ant-covered bowls and plates or wiping down ant-strewn counters that the little buggers are still crawling on me.  Intellectually I know it's unlikely they can cause any real harm, but just thinking about it gives me the creepy-crawlies.

But out in the wild - or at least my back yard - ants are really interesting to watch, especially when scouts lead their colony-mates to a food source or mobilize when their colony is in danger. Clearly while not particularly clever as individuals, communication between colony members allows them to function effectively as a group.

Evolutionary biologist E.O. Wilson is one of the world's leading experts on ants. Here he explains at World Science Festival how ants use chemical signals communicate:

The quote at the beginning of this post is from E.O. Wilson's history of an ant colony - "Trailhead" - published in the New Yorker. Wilson's anthropomorphic descriptions of ant communication work pretty well as fiction, but he may be oversimplifying what happens in an ant colony.

For more detailed look on the complexities of how an ant colony functions check out Stanford biologist Deborah Gordon's TED talk about her research on harvester ant colonies in the Arizona desert:


(note: you can view the video with captions on the TED talk page)

The "haphazard" interactions she's observed sound a lot messier as a form of communication than the chemical "statements" described by Wilson.

Why does that matter? Figuring out the details of how ants are directed to perform specific tasks could be used to develop ways of naturally controlling invasive ant populations or preventing home invasions with some sort of "Danger, keep out!" signal. That's a result I'd like to see.

Top Image: ant on a mustard flower by me

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She mates and she kills

Oct 07 2010 Published by under Biology & Environment

Redback Spider

Miss her, kiss her, love her, wrong move you’re dead

If yesterday's post about black and brown widows made you want to learn more about venomous spiders, you should check out DN Lee's latest post at SouthernPlayalisticEvolutionMusic. Her look at sexual cannibalism in Latrodectus spiders (like black widows) is set to Poison by Bell Biv DeVoe.

Alternatively, if you prefer your cannibalistic spider-like creatures in science fictional form, you should read James Tiptree Jr.'s "Love is the Plan, the Plan is Death".  If you don't have a copy of Tiptree's stories,  you can read the Nebula-winning tale at the old SciFiction site (dead, but still accessible through the Internet Archive).

When I see your littlest hunting claws upraised my whole gut melts, it floods me. I am all tender jelly. Tender! Oh, tender-fierce like a Mother, I think! Isn't that how a Mother feels? My jaws are sluicing juice that isn't hunger-juice—I am choking with fear of frighting you or bruising your tininess—I ache to grip and knead you, to eat you in one gulp, in a thousand nibbles—

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Good news, everyone! Brown widow spiders have arrived

Oct 06 2010 Published by under Biology & Environment

Black widow hanging out on my planter

I don't like spiders. I know, deep down, that they are unlikely to hurt me, and that they eat flies and other pesty insects.  Even so, I have a visceral reaction when a  spider crawls into my vicinity. I'm pretty much OK with spiders that stay outside (although stumbling on a big one, like the one Zuska found on her rain barrel might cause me pause1).

But black widow spiders (Latrodectus hesperus) are another  story. They are indeed venomous and their bite is supposed to be quite painful. Just reading about the symptoms makes me cringe:

Severe muscle pain and cramps may develop in the first two hours. Severe cramps are usually first felt in the back, shoulders, abdomen and thighs. Other symptoms include weakness, sweating, headache, anxiety, itching, nausea, vomiting, difficult breathing and increased blood pressure.

But no one in the U.S. has died from a black widow bite in over a decade, so it's not that bad, right?

Fortunately, black widows rarely end up inside the house. Instead they make their webs in dark nooks and crannies, usually only coming out after dark or if they are disturbed.  Their amorphous webs - straight from a haunted house - are pretty easy to spot and sweep away.  They leave me alone and I pretty much leave them alone.

Brown is apparently the "New Black"

But then one of the local newspapers had to run an article ensured to freak me out a bit: "Brown Widows Now in Inland Area"

Brown widows (Latrodectus geometricus) are cousins to the  black widow. They are more drably colored than the black widow, with brown bodies and an orange or yellow hourglass on the abdomen.  Brown widows are originally from  South Africa, and have been working their way west from Florida for the past 10 years or so. Only recently have they appeared in Inland Southern California.

How do brown widow spiders compare to black widows? According to the article:

  • Brown widows are more abundant than black widows. According to Rick Vetter, who studies spiders at UC Riverside, "Where you might find six or seven black widows in a backyard, now you find 100 brown widows."
  • Brown widow venom is twice as toxic as black widow venom.
  • Brown widows live in more open locations - such as under patio chairs and in chain link fences - than black widows

They sound pretty nasty, right?  I'll admit I went out to my patio and made sure there weren't any webs on my plastic patio chairs shortly after reading the article.

But the real story - easy to overlook among all the scary-sounding description2 - is that brown widows are much less likely to bite than black widows, and when they do, they don't inject as much venom. That means that they aren't actually considered to be dangerous.

As the UCR Spider Research site explains:

A South African medical journal reports on the bites of 15 brown widows in humans (Muller 1993) . Only two symptoms of brown widow envenomation were reported in the majority of bite victims: 1) pain while being bitten and 2) a mark where the bite occurred. That's it. Not much more. The bite of the brown widow is about the same as any non-poisonous spider. It hurts and leaves a little mark on the skin. It is no big deal. There are none of the serious, protracted symptoms that one would exhibit when bitten by a black widow.

So the appearance of the brown widow really is good news, at least from the public safety perspective, because they may be displacing the black widow, which is dangerous.

I'll still be happier if I never run in to one.

If you want to help track the spread of the brown widow spider in California, you can mail any brown widows you find outside of San Diego, Orange, or Los Angeles County to Rick Vetter at UC Riverside.

If you are in Los Angeles County, you can also participate in the Los Angeles Spider Survey, sponsored by the Natural History Museum of Los Angeles.

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1. Where "pause" means that I get my husband to move it away from any outdoor equipment I want to use.

2. Especially when the article concludes with advice from an entomologist with the National Pest Management Association who advises (not surprisingly) dusting with pesticides or calling an exterminator. "Kill them all" seems a bit over-the-top advice for non-dangerous spiders.

Top image: By me.

Bottom image: thumbnail of graphic from the Press-Enterprise article "Brown Widows Now in Inland Area". Click the thumbnail to see the full-sized image.

19 responses so far

Stinkbug Invasion

Sep 01 2010 Published by under Biology & Environment

Healthy Sweet Alyssum

One of my favorite flowering plants is Sweet Alyssum: it's low maintenance, heat and drought tolerant, and flowers year-round (at least here in Southern California).  Since it grows low to the ground, it makes a nice addition to the pots with seasonal bulbs, which would otherwise just be bare dirt for a good part of the year.

Because Sweet Alyssum is usually so easy to grow, I was a bit surprised to see that in several of my pots it was starting to look dried out and sickly. Even though there was a heat wave last week, my other potted plants look just fine, so lack of water was unlikely to be the problem.

On closer inspection of one of the plants, I noticed that it was swarming with little red beetles. My first thought was "Yay, ladybugs!",  since they are great for controlling insects pests like aphids.  But when I looked a bit closer, I noticed their markings were more ornate than the simple red-with-black-spots of ladybugs. And while the bugs were teeming on the Sweet Alyssum, other nearby plants appeared bug-free. What could they be?

Painted Bug (Bagrada hilarus) eating my Alyssum

Painted Bug (Bagrada hilarus) eating my Alyssum

After a bit of research I identified the critters as the Painted bug (Bagrada hilaris) or Bagrada bug, a type of stinkbug. It is an invasive species native to East and Southern Africa that first appeared in Los Angeles County in June 2008. Last year it reached the inland low desert. And now it's widespread in Southern California and western Arizona.

Bagrada bugs primarily eat Brassicaceae, a family of plants that includes cruciferous vegetables such as cabbage, mustard, broccoli, cauliflower, radish, turnips, and kale.  Sweet Alyssum is an ornamental Brassicaceae, which explains why those plants (and only those plants) were infested.

Unfortunately Bagrada bugs are quite hardy, and resistant to most organic methods of control. According to the UC Riverside Center for Invasive Species Research the heaviest Bagrada infestations are in "organic farms, community gardens and residential vegetable gardens where little or no pesticides are used."  The easiest way to control them without pesticides is to remove the infested plants, cultivate the soil to kill the unhatched eggs, and squash any bugs that remain.

Lots of stinkbugs!

So that's what I've done. All my Sweet Alyssum is gone.  Fortunately I'm not growing any other members of the mustard family, and there aren't any reports of the pests attacking tomatoes or eggplant or zucchini or the remaining ornamental plants I have growing in my yard.

I probably won't try to grow any related plants in the future, since we live adjacent to a field with mustard plants growing wild. A natural reservoir for the pest.

But while my garden will easily recover, the rapid spread of Bagrada bugs has the potential to be a serious problem for Southern California's organic farmers. Hopefully, they won't end up on the state's 10 most (Un)wanted list.

All photos on this page by me. Click to see larger images.

More bug photos:

Note: Comments  are back open.

4 responses so far