Plasma Locust is an attempt by Plasma Lash to take a more offensive role in combat; even his STR reducing tactics can involve damage when powered with a Yellow Spike.
Plasma Locust 1.0 is capable of dealing more damage than Plasma Lash 2.0 if you play your cards right, those cards being lots of EN to spare. Thankfully, it can stockpile EN with Headbutt to save up for such expensive attacks.
It is also notable that Plasma Locust is considerably more expensive to the swarm than Plasma Lash for the cost of the swarm. Keep in mind that Plasma Lash 3.0 costs only 10 more SV than this little locust.