Highly mobile flying bots that shoot low-powered bolts quickly and frequently. Not particularly threatening, but a swarm will harass and annoy you until you either leave the area or kill them.
They will jink away as soon as they see you aim at them, so the best tactic is to 'flick fire' by quickly tracking across the screen and press fire when they line up, or when they strafe to where the fire will be. Spamming also works if you have a rapid-fire gun, as they can only move so far, so fast.
For a more tactical approach, fire around them. aiming just next to them. They tend to strafe anyway, so may fly into the fire zone. Use of mods like Mines and Firemines also let you set up traps they ignore and easily fall prey to. The simplest tactic is to run around a corner and mine the edge of the wall. The Twerps will trigger the mines as they try to follow you.
Bounce mod or bounce-enabled weapons like the Portable Pizza Thrower can also be used. Twerps don't calculate where the bounced fire will end up, so they are easily deceived. With the Hedgehog or the Pizza Thrower (or bounce modded gun), the easiest thing to do is move backwards in a (nearly) straight line while firing continuously at the floor right in front of you. The twerps will follow you, and not try to avoid the fire jumping up in their faces.
Twerps do small amounts of damage but can be very distracting. In hectic rooms focusing on the Twerps first can be dangerous as all the other turrets still want to kill you. It is best to ignore Twerps and focus on deadlier targets, or find a quiet part of the room where you can take out the Twerps in safety.