[Venger]

Depends on how detailed and close you want to get.

You could hold the insect/spider in a spi-pot (essentially, it's trapped to the base by a piece of foam - but you'll be looking at it through perspex.)

Otherwise you'll have to kill the spider and store it in spirit (and create a collection), however unless you're really into spiders/ involved in the recording scheme or scientific research I'd advise against it, but that's my personal choice.

Do you really, really need to get down to species or will genus do?

hope that helps.