The Insolum Beetle's exoskeleton was extremely tough; however, Izroth was able to slowly chip away at it piece by piece using the exposed area where its wing once existed as a starting point.
In truth, while the Insolum Beetle possessed a large amount of HP due to its status as a world boss, its HP was on the lower end compared to other world bosses around its level. This mostly had to do with its high natural defense and strength.
In terms of raw physical prowess, even Izroth, with his Heavenly Golden Body and the Ring of the Ancient Colossus effect active, could not compete with the Insolum Beetle head-on.
Not to mention its mobility and magic abilities could also not be underestimated.
Overall, the Insolum Beetle was unbelievably well-rounded in all aspects except one—its health. There was also the fact that it was not used to fighting other strong opponents. After all, it likely ruled over this section of the Ferae Jungle without contest.