Along with the stronger migos, assassin bugs are a major reason that one cannot just ignore the summon insects spell and use it solely as a buffer, as is possible in vanilla NetHack. Assassin bugs are very fast, with a speed of 24, and are more than capable of dealing large amounts of damage, particularly to a character who is focusing on the priest next to them. A good strategy for dealing with summon insects is to take out the migo warriors, killer beetles and assassin bugs, and let the rest of the a serve as a buffer.
This is a real insect. A terrestrial ambush predator, injecting lethal saliva that liquefies the insides of their prey, which they then suck out.