All the insect in front of our parapets

This great ant-spider the size of a whale. Covered in a thick bumpy exoskeleton that resists the concentrated force of our rifles and cannons. The cannon crew where aiming for the terrible eyes, like massive gems but the creature moved around too fast. Snagging men from the wall and chewing them up fine with long barbed side jaws. Its then I had the idea. I began heaving buckets of black powder all over the monster's face then I pitched a torch into its eye as it came in to eat me. The smell was ghastly. Snaps and pops and a shrill agonized insect cry that still haunts my dreams. The insect monster writhing blind with a party melted face among the invaders, crushing them. Rending them apart it its pain panic. The attacked its under sides, the soft parts with sabres and rifles. Meanwhile he attacked them, firing round after round. When the smoke cleared the monster was dead and the remaining invaders where running away. Many had dropped they're guns and provisions.