For future reference:

When attempting to photograph the slow mutilation of a butterfly caught in a spiderweb by the spider inhabiting said spiderweb, a few simple guidelines will avoid disaster, embarrassment, and realisations of grand dickheadedness.

Guideline #1 - If you are unsure of the make and model of the spider, and therefore it's capacity to be scary, it is best not to approach it while alone in a remote location.
... too late.

Guideline #2 - Thoroughly suss out all web attach points. These things are in essence a suspended snare. They have to be tied down somewhere, and severing one of the ties is likely to bring the whole intricately woven contraption (containing spider with possibly unidentified levels of scariness) into a state of being sprung and wrapped around the unwary photographer's entire body, with variable and unpredictable placement of the occupying spider.
... close. Accompany a brush with an attach point with a loud FUCK! Oh thank FUCK! Sneaky little FUCKER! and you have an accurate representation of events.

Guideline #3 - Use a long lens to get in close rather than put yourself in the firing line.
... too late.

Guideline #4 - Make sure it's not windy. Either this or bring some marvellously fat friend with you to conveniently provide a wind break. Otherwise, two disastrous things could occur... One, ninety percent of your shots could be a waving blur of unrecognisability. Or two, you could be in as close as you possibly can with your short lens and end up wearing half the intricately woven snare. In this case you will resort to dancing around in bodily jerks, slapping and grabbing at every available surface with your hands in an attempt to remove the sticky web and the occupying spider (possessing unidentified levels of scariness) from any possible resting positions.

... too late.