"There are many organisms that predigest tissues externally before
"consuming" them;
spiders are probably the most notorious."

Assassin Bugs are one of our most common insect-bite enquiries. Their bites
have no toxin but strong enzymes that break down the tissue of their prey to
a soup, that they then suck up through their rostrum. When they bite humans
in self defense it hurts like fury and causes tissue death in a small area.
I assume the ones in North America also bite people now and then?
This site has a link to our information leaflets including the one on
assassin bugs. http://www.qmuseum.qld.gov.au/inquiry/leaflets/index.asp .
There are some great illustrations amongst those leaflets, done by various
illustrators and even volunteers and work experience students over the
years. They are mostly done on scraperboard (scratchboard).
I have always liked the top illustration on this leaflet done by my friend
Robert Allen http://www.qmuseum.qld.gov.au/inquiry/leaflets/leaflet0021.pdf
. I asked him at the time where he got the image of the dog and I think he
said it was from growing up with lots of dogs. His phenominal ability to
draw lifelike images from memory staggers me.
Cheers,
Geoff