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Christmas Bells - Blandfordia nobilis

Tuesday, February 21, 2012

Anni's Black House Spider

My friend Anni bumped into me yesterday morning, in the village, and mentioned that she had a Spider which had worried her. As Anni and Andy have Elsie, a toddler, you can join the dots of that conversation yourself.

But Anni had collected the Spider so I could get a proper ID on it. She wanted to know what she might be dealing with, and what is the appropriate action, should this situation arise again, in the future. An eminently sensible approach, I thought.

When I first saw Anni's Spider, it was all shiny black, and quite wet. Seems lots of spray was used to "subdue" it. Oh well, at least the specimen was not squashed unrecognisably by a pair of Hob-nailed Boots. That meant I could get some decent photographs, and examine it in detail.

At first we were not sure if it was a venomous spider, but I thought not.
Anni had already done a thorough check of the appropriate websites for the Sydney Funnel-web Spider, and had ascertained that it lacked the tell-tale spur on the second leg (a device used by male Funnel-web Spiders in the mating ritual with a female Funnelweb). 

I searched for the obvious Funnel-webs and Trapdoors, but both seem to have a shiny "cephalothorax", which this Spider does not have. They also both have very large, prominent fangs, which it seems are quite hard and shiny (useful for serious penetration of hard exoskeletons of their prey - insects). This one's fangs (Chelicerae) have large "mandibles" (the main structural unit of the fangs) which are noticeably hairy, and the pointy bits (true fangs), are barely visible, so they must be small.

The Primitive Spiders, including the Mygalomorphs - the Funnel-webs and Trapdoors we tend to worry about - evolved about 250 million years ago, somewhat before we mere humans appeared on the earth. So Spider anatomy is not designed to harm us. They are natural hunters of insects. Any damage they might cause to humans is virtually incidental to their true function as hunters of insect prey.

So, after a bit of close examination, and some on-line research, we figured it probably was not one of those Spiders - you know the ones we all dread. We all know that they are likely to roam in Summer, especially after rain, when their burrows get flooded. But I was confident that it wasn't either of those Spider families.

The next most likely option (in fact it always was THE most likely option - but one likes to exclude certain "nasties" from the list firstly) was the relatively harmless***, and very common Black House Spider, Badumna insignis.

Black House Spider with $1 coin for scale (24.8mm diam)
You can see how dark it was initially, with hardly any markings visible.
That situation changed after a while as it dried out.
And with the use of a strong flash, markings became more discernible.

I concluded that it was a Black House Spider, Badumna insignis
Black House Spider laid out for ID shots
One leg is missing. Spiders have a quota of 8 legs
 OK - now if you have stuck it out so far, kindly leave this site now, if you are at all Arachnophobic - as the following shots are ultra-close ups, taken and displayed here for identification purposes only.
You ought not be here anyway, if your a bit on the timid side - the title of this post told you what it was about.

OK Here we go.
This is a face on view - to show the layout of the eyes.
Modern Spiders have different layouts of the eyes to the Primitive Spiders
Primitive Spiders usually have 
two rows of small eyes in the centre of the head.

This one has two large eyes in the middle of the head
four tiny eyes below those two main eyes
and it has two more quite large eyes higher up,
which are positioned well to the side of the head.
They presumably give it good "all round vision".
A handy defensive set of eyes.
The fangs, which are vertically aligned, are quite hairy.
The two structures either side of the fangs are the "palps"
(strictly "pedipalps")
which are part of the mouth feeding system.
They are not classed as "legs", 
although they have some structural similarities.

Click on image to enlarge it, to see the details.
Face and "mouth" of the Black House Spider
Side on view of head of the Black House Spider
This view shows the extra eye - set back and to the side
from the main large eye in the centre of the head.
The tiny eyes are just visible in the lower row.
Click on image to enlarge it to see the details


My favourite image of this Black House Spider
it shows the key position of those two main eyes
directly above the fangs.
The four tiny eyes are also strategically located
and they are clearly visible in this shot.
Click to enlarge this shot.

 *** says of the Black House Spider that: "People are rarely bitten, but some cases of distressing reactions and illness have been reported."

Now you can all relax.
Good Night.


Anonymous said...

I am so happy I have moved to the UK, haven't seen a spider for months now :) Cheers Brent

Denis Wilson said...

Hi Brent
Are you putting your hand up as an Arachnophobe?
Good to hear from you.
Did you manage to avoid the big freeze which seems to have hit the rest of Europe?
Hope so.