I'm usually up close with an AR or Shotgun so once the crystal has an open spot, the Hellbug usually gets wasted in the process before getting the chance to evolve. That hasn't really been a problem in the Arkfalls I've been in but I've only done a handful (I usually participate if there are 10-15 people, not too fond of the larger ones but I usually end up in those when taking on the massive bosses at the end of major ones so I just stick around anyways).
this only applies to ones where you have to destroy the arkfall not the one with waves.
Red Arkfall Hellbugs: Avoid as best as you can/reasonably killing the skitterlings.
Blue Arkfall Hellbugs: Kill them. Kill them all. Faster you kill the more waves(bonus waves exist on it) for more loot/exp.
I farmed my 2500 Major Ark Fall kills on the Skitterlings at the hell bug events :P
Yup as the above posts mentions. you need 2500 kills in arkfall and the sitterlings are one of the easiest ones to get it on. even if u shouldnt kill em you will for the achiev. :-)
Y'all whine too much.
Nilxain's Warmaster Guide
^^^MUST READ^^^
Siggy done by the ever-talented Ensu