Re: How to sustain a small spider, and some larvae, alive?

To keep your spider alive I would suggest putting it in a plastic tub or 
jar with some netting over the top and catch some flies about the same 
size as the spider. If you put some twigs in the tub as well then it can 
have something to make a web in, then just put 1 fly in and see if it 
catches it. Also spray the tub lightly with a fine mist of water so the 
spider can drink. I kept a british garden spider in a bucket for a week 
using this method (I eventually let it free after making observations). If 
you can identify what species or at least what type of spider you have 
then you can find out its preferred food. You can also buy fruit flies 
from some companies or pet shops which will make a good food source if you 
can't catch any yourself.
As for the larvae you will need to find more acorns to feed them with 
preferrably from the same area you found the others. Then just keep them 
in a jar with the foodplant and mist with water occasionally. To stop the 
foodplant from wilting put the stems into a small pot of water with some 
oasis or gravel but make sure the larvae cannot fall into the water or 
they will drown.
Again if you can find out what species the larvae are then you may be able 
to find better ways to care for them. Many pet shop websites or specialist 
insect suppliers have detailed information about rearing minibeasts. A 
couple of sites I have used before are:

www.small-life.co.uk
www.insectpets.co.uk
www.easyinsects.co.uk

I hope this helps and I wish you luck with your minibeast friends!