Shooting the moth which dallies along at the top of your screen will gain extra speed, but only for the current level. Weirdly, you shall hear "Nairobi" when you kill it but this makes sense once you've read the docs. Yeah, I know... who reads the docs? Every eighth level a "parents" turns up for a battle which makes a nice boss fight that isn't too difficult and doesn't ruin the momentum so you're soon back fighting the insect hoard once again.
I seriously doubt that Llamatron fans will be convinced by Insecticide but it is a fantastic game in its own right and definitely worth playing. What it lacks in originality it - more than - makes up with great gameplay, jazzy colour cycling and sampled sounds. I've enjoyed this silly alternative to the Robotron theme. My final word: Nairobi!!!!!
Download the newly updated version of Insecticide released only yesterday :-)
Ironically, it's had many bugs squashed so should run fine on all computers [thanks PP!!]