This might need further testing, but I think this HNM only pops at night time. Those Mages that still needs these pumps, just for testing purposes see if it keep popping out Exo's during the day, and the Alastor Antlion, only at night.
It's Immune to Shadowbind, and last time I fought this beast, the feeler spawned about 12 Exo's before Alastor, which happend to pop at night. Just some info on this Beast!
Hope it helps.