The large citrus butterfly larvae has one of the coolest defense mechanisms I've seen on any bug. Firstly it obscures itself by giving the appearance of having been left behind by a bird. If the disgusting look is not enough to deter something having a peck at it then come out the horns... literally. As you can see the bright red 'horns' protrude just above it's head and retract again once it feels safe. The 'horns' apparently produce a foul odour as well, though I can't say I've been tempted to verify that one. They do some damage to my citrus but not enough to warrant killing them. Heck, they turn into large butterflies who'd want to kill them anyway? Pic 1 is of a bigger grub but I think it must have been on the verge of 'cocooning' as it wouldn't be stirred. Pics 2-4 are of a smaller grub that was a little more active. I was going to post it in pests and disease but think this guy's cool enough to be in this section.