Unlucky Fly – Macro

October 09, 2011  •  Leave a Comment

Out in the garden yesterday I was shooting more macro images of spiders and other insects when I had the opportunity to witness a fly get caught in the web of an Araneus Diadematus (Cross Spider).  I took a few shots of the events that followed.

If you’re seeing this in the “Blog Post” list of my site, I’m not going to post an “intro” picture here as the content is pretty graphic, so if you’re scared of spiders, you really are advised to not go any further…

So, to start – the fly hit the spider web at about 14:57:00.  The buzzing attracts Little Miss Spider (I’m fairly sure it’s a female) who appears from under a leaf at the end of the web and skitters across the threads with amazing grace to the fly.  She appears to grab the fly and manipulates it’s position so she can start to wrap it up:

Fly in the Web - 14:57:13

In under 30 seconds, the fly is trapped, encased in a cocoon with absolutely no chance of escape:

All Wrapped Up - 14:57:52

Over the next minute, the spider rolls the wrapped fly around, eventually getting to the right position and injecting it with digestive enzymes.  Spiders have a very narrow digestive tract and can only cope with liquid food, so they inject enzymes to break down the internal tissues, then suck out the liquefied remains.  Lovely.

Injecting - 14:59:08

At this point, the fly is probably dead – if not, it hasn’t got long left.  I’m not sure of the origin of the droplet on the back end of the fly in the shot below:

14:59:34

I believe the digestive enzymes take some time to properly work, so the spider does some further wrapping.  The shot below shows the state of things around 3 minutes after the fly entered the web:

15:00:42

And in this close-up of the picture above you can see the spinnerets of the spider in action, with silk being produced:

15:00:42

Spider silk is absolutely fascinating, and the production even more so.  The spider above (an Araneus Diadematus or Garden Cross Spider) has at least 6 specialised glands to produce different types of silk for draglines, temporary scaffolding, capturing prey, wrapping and bonding.  There’s lots more information over at Wikipedia here.

The final shot below is the most graphic.  12 minutes after capture, the digestive enzymes have worked to liquify the tissues of the fly and the spider is sucking up it’s food:

15:09:00

I’m fascinated with spiders since properly starting to research them about 18 months ago, and while I understand their nature to some extent, it’s still pretty gruesome the way they digest their prey.

Technical Info

All were shot with a 7D and Canon 100mm f/2.8L IS macro lens, handheld, between ISO 100 and 400.  Some used flash, others (where I wanted a shallower depth of field or to try and remove the flash glare) did not.  Where using flash, I use manual exposure mode and adjust flash exposure compensation, usually down a stop or two.  I use back-button focussing in AI Servo mode to get the ability to either be in continuous AF or locked focus with the press or release of a button.


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