Spontaneous generation feat. bisecting things is fun

So something happened today which would neither surprise nor impress someone who actually had any experience studying spiders. But this is my first year of it so I’m going to bring it up anyway.

So I had spiders in my house over the summer for observations and some of the females laid egg cases.

Female C. foliata and spawn

These were roughly spherical orbs slightly less than 1cm in diameter which would be hung from the roof of their mesh cages. Sheet-webs in the wild will incorporate forest floor debris into the egg casing. In the case of my spiders their cages were a little Spartan so they had to make do with the left over legs of the insects I had fed them.

When the females died I removed the egg cases and kept them in little pottles (plastic jars), trying to keep them suspended if I could. Demonstrating an innate aptitude for husbandry, these various eggs were starved of oxygen i.e. lids on until I realised this was dumb; they were exposed to extreme desiccation i.e. left on the window sill during the summer; and then they endured several months of Auckland winter in a cold student flat.

Then I read somewhere that, in some cases, the female spider actually has to open the egg case for the young to escape.

Needless to say, when I brought a couple of the egg cases into the lab a full 6 months after they were laid, I was expecting, at best or at worst, to open up the sacs to find puckered, charcoal eggs. Either that or the bodies of hundreds of spiderlings squashed together until they were indistinguishable or utterly dismembered, mutilated in the Battle Royale which I had imposed on them with one engorged baby spider lying prone, ultimately unable to escape the silk prison.

battle royale
Amazingly, only two males were cannibalised

The outer casing of the sac is white with the feel of a tough napkin which I had to cut through with my dissection scissors. On the inside there was a cluster of eggs (each egg <1mm diameter) held together with an off-white cement. This cluster hung in the centre of the sac, suspended in fine, kinked threads which came in every direction from the inside surface of the outer sac.

A nice word for it would be that the eggs sat in a harness, a more amusing one would be that the egg sac is basically a spider zorb.

(The block of eggs broke)

I pulled some of the eggs away a cut them open but the magnification on the dissecting microscope wasn’t really up to the task of distinguishing the contents. The eggs themselves ranged between dark brown and pale orange and some did indeed look pretty much dried up and there wasn’t a whole lot of evidence of anything breaking out of the egg.

egg 1 bissected


But it was at this point while I was looking at a block of the cluster that had broken off that I saw little pale blobs moving around. I think that they might be mites.

You can see some little orange legs just above the top egg.
egg 1 friend
The suckers are <0.5mm and move around so I couldn’t really get a good focus on them. You can see the pale oval (it’s abdomen) with an orange head on the dark egg.



egg 1 single 2 marked
egg 1 friend marked As a hint


A similar surprise met me when I opened up the other one, albeit a more…plentiful one. This egg was almost completely full of what looked like fine grain sawdust but *surprise* the sawdust is little animals!

Who fancies some granola?
Egg e4
Yep. ALL of the little pale ovals are…arachnids of some description

If these things are mites then it looks like they have chewed up the eggs hence the mess.

What does this have to do with anything? Not a whole lot. I have the animals in a mesh cage in the lab at the moment and will try to rear them in the time honoured tradition of “let’s see what happens”.

I like an animal which can survive in spite of me.

(Here’s a quick sketch of them (the abdomen isn’t big enough). Makes me think mite).