This movie freaked me out as a kid when I saw it back in the 1970s. The bugs had two organs on their abdomens that produced electric sparks. The scene that ended up giving me a nightmare was the one where a bug crawls up in a woman's hair and sets her head on fire.
The bugs had super-thick exoskeletons and couldn't be crushed by normal means because their contents were under intense pressure. The antagonist used a knitting needle to pierce one and it exploded.
He cross-bred the bugs with regular cockroaches...which proved to be a bad move.