Thursday, August 20, 2009

Tree guards, bagworms and argiopes

Its been an interesting fortnight.

# Went on tree walks with toddlers and teenagers.
# Rambled at the PWD park, with the sun, bees and butterflies for company.
# Saw pictures from Chandrika of a creature that looked like it had come from some alien land.
# Learnt that cycle tires can make good and cheap tree-guards.
# Discovered an argiope inside one of those tree guards.
# Saw scores of black kites all of a sudden.
# Have been tracking an ugly little "crowling" grow into a handsome large-billed crow, all set to fly.

The tree walks and the PWD park ramble were courtesy Nizhal, that wonderful, enthusiastic band of tree lovers of Chennai. Their volunteers go around, in different localities and parks of the city, with different groups, taking young and old on walks to familiarise us with the trees of the neighbourhood, and hoping to spread awareness and commitment for saving our trees.

May their tribe grow.

One of the projects which is currently consuming their time, energy and attention is the PWD land/park in Kotturpuram on the southern bank of the Adyar river. Local species are being planted in order to make a tree park - no lawns or concrete walkways, is what I've understood it.

It was here that a bunch of toddlers came, to plant a few saplings and get sensitised about the need for trees.

The planting was done with much enthusiasm, as also the chasing of butterflies and mynahs. The high point was finding an earthworm in the soil as they planted, and there was many a "ewww" from the girls, while the boys fell strangely silent, taking a tentative step backwards, as Deepika extended her earthworm-filled hand to display it better!

It was here that I learnt that discarded tires make cheap and quick tree guards.

Nizhal volunteers come on Sundays, and quickly put these together, through some clever entwining of binding tape. There had been a couple of showers and so the ground was covered with green undergrowth, and I quite enjoyed hanging out there, never mind the sun.
So it was that I volunteered to go and check on the saplings one Tuesday morning - the saplings do need to be tended - and made an interesting "discovery. More about that later.

The case of the Bagworm moth

On returning home, I found a strange email in my inbox, titled "strange flower feeder". Chandrika of MNS posted these pictures:

See the head poking out
Well, it was my turn to go "eww", as I stared at my computer screen! It turns out, that Chandrika was testing her new macro lens, and found this in her own garden in Thiruvanmyur! Talk about urban wildlife! I was sure that no one would know what this strange creature was.

I had obviously under-estimated the "pros" of MNS. Quick came the replies - thats a bagworm moth larva, dear, go look it up! And so I did. It turns out that larvae of this moth family build their cases out of any old debris they find around - twigs, soil, leaves - as soon as they hatch. The binding is a kind of silk they secrete.

Now, as it grows, it carries this case and moves along, and the caterpillar pokes it heads out to feed on the leaves of the host plant, like any hungry caterpillar. When it is fully grown, it anchors the case to a branch and seals the opening. It then develops into a moth. If its a male, its lucky, it grows wings supposedly and then flies off to find a mate.

But if you are born a female bagworm moth, then life cannot be much fun - you are stuck in that case, you lay your eggs in it and then you die!

If that was not interesting enough, my next visit to the PWD park revealed yet another mystery.

St Andrew's Cross

It had rained insistently for a couple of days, and so the park looked even greener. The undergrowth was wet, the little meadow flowers were buzzing with bees, and as the sun was up already, the butterflies were going crazy chasing each other.

My visit was supposedly to take a look at all the saplings and report back on their state. So I dutifully, stuck my head into every tree guard, to make sure the sapling was alive and well.

And I was rewarded with this!

I stopped short and stared. I have never seen such a large and complete web in my life. I swear, it was atleast 2ft by 2ft.

Hmmm, but it seemed to have only four legs, and as far as I knew all self-respecting spiders have eight.

Oh look, its actually taken some of the binding tape and woven it into its web! ( or so I thought.)
I came home, and my first spider image hit was this. And I had identified my spider!

Not four legs, but eight, held together in an "x" cross. And so the reference to St Andrew who was crucified on a cross like this and not the standard crucifying cross.

Here's some more interesting stuff about Argiope:

Besides their standard orb-web, Argiope spiders build additional white opaque zig zag lines on their webs, called stabilimentum.

Sometimes the zig-zag lines match their leg positions, which lead some people to suggest that this helps give the appearance of longer legs. Some spiders build a single vertical line, yet others a patch of zig zags in the centre of the web. No matter the design, the spider sits right smack in the middle. We do not know the purpose of these lines, but some of the explanations put forward include:
They stabilise the web (hence their name!)
They warn larger animals in the same way that safety strips on glass doors warn people from walking into them. Thus the web is protected from damage by flying birds.
Research has shown that the silk in the stabilimentum reflects ultraviolet well, unlike the silk used in the rest of the web. Thus, the designs may mimic flowers, which also reflect ultraviolet light well, and often have lines to guide insects to honey like airport lights do for airplanes. Instead, the insects are guided to the spider which sits in the centre!!
Source: The Mangrove and Wildlife at Sungei Buloh Wetlands Reserve.

And I had thought that stabilimentum was the twining tape!! According to this website, Argiope mangal puts out two stabilimentum, and Argiope versicolor puts out four. This one has three!

I also discovered that there is a site on South Indian Spiders.
And guess what. I could not find this chappie there. (Actually, its a lady - only lady spiders build webs...So what do the male ones do for food? I need to find out.)

I cannot find any India mentions of this spider. So, is my id wrong then? or is this some stray imported spider which shouldn't be here?

Somebody help!

The Madras Club cupola above the grand trees, on the opposite bank of the estuary.

Look under those leaves and rocks, folks, you never know what you will find!


  1. Lovely ! Great pictures too. Good to see that there are citizens that care about environment

  2. Hi,

    Interesting to read ur blog..hey ur doing some great awareness through ur notes...keep it going.


  3. i saw this one too! i did not get a good look at the body though.

    Look at this one --

    Preston identified it as the Striped Cross / Striped Fourleg (Argiope aemula) -- on some days it has 4 stabilimentum, on other days 3 and sometimes just 2.

    The web is really big -- am sure it is atleast 2ftx2ft.

  4. Thank you Bhanu and Avdi!

    Arati, thanks for the link! I just did a "zoom-in" on your spidey, and thought the markings were a bit different?

    This one does not have those distinct lines that yours does. What do you think?

  5. Great post flowergirl,
    I am partial to Argiope spiders. The males of these are puny and they share the same web space with the big female. I tried very hard to put a name your one. The details I can read from the image is not suffcient due its image-size. But, if I am asked to identify it at gun-point, I would say A. pulchella.

    Thanks for that excellent spider website.

  6. hey

    nice pics.. looks like u've had quite an adventure... I had been on a weekend trip, and during a coffee trail inside a coffee estate, saw this tree completely engulfed in cobweb.. like cotton candy.. will send u link , chk it out! :)

    am from Chennai too!!

  7. Great post...nice idea about using old/used tyres. Good way to reuse them. I think u shud have given the spider a separate blog...she deserves it. I have seen these big girls in many places around Southern India (saw a beeeeg one near Doodhsagar, Goa) and hence equally surprised that this is not mentioned in the guide. Interesting to see Sungei Buloh wetland reserve mentioned as a source. I must shamelessly plug my own blog on Sungei Buloh altho that was more about the Monitor Lizards than anything else. Here's the link from my archives:

  8. Lovely post, neat images, cool.

  9. Thanks Amila...the male was missing in my web...or maybe I didnt look hard enough!

    Aarti, just read about your coffee trail trip, as well as other trips to Sringeri and belavadi!

    Capt Murthy, thanks for the link, and yes, it looks like these argiopes are all over the place! I should go back and get better pics...

    Thank you T and S! Coming from you, I am very flattered!

  10. Ah, I missed this one...
    But I'm glad you showed me it.
    St Andrew's spider's quite sinister
    just waiting for his prey to sit!

    This rhyming habit of ours?
    Others are going to curse!
    But to add spice to life each and every time
    Lets post each other in verse!

    'mistio' - word verification for this comment!

    Guess I mistio all on my blog!

  11. Dear Flowergirl, am happy that you commented on our webspace that I got a chance to go through yours. Love your nature filled pages. It is amazing how we go on to explore similar aspects of life and wonder about them at same time. You posted this on 20th and I talked abt the same spiders on 24th hehe. So at last you found out their names and they have indeed 8 legs! Yes the world outside have a lot more tricks and tactics and wonders to keep us amazed. Will keep crawling through your pages :)

  12. have also added your web to my feed reader. cheers,,

  13. Yes, Rocksea, I guess one goes through a similar learning curve?!

  14. Hi

    Argiope spiders are found abundantly in my backyard. Just yesterday i photographed one.I stay in Bangalore.

  15. Hmmm, thats interesting Aasif, and here I thought I found something not so common!

  16. where do we find volunteers who can plant trees in our neighbourgood?

  17. Anonymous, do get in touch with Nizhal, if you have somebody who will care for the saplings once they are planted.

    In Nizhal's experience, the planting is not difficult, it is the looking after that is.

    Maybe you could be the volunteer for your neighbourhood?