 Spinosyn A does not appear to interact directly with known insecticidal-relevant target sites, but rather acts via a novel mechanism.Spinosyn A resembles a GABA antagonist and is comparable to the effect of avermectin on insect neurons.Spinosyn A is highly active against neonate larvae of the tobacco budworm, "Heliothis virescens", and is slightly more biologically active than spinosyn D. In general, spinosyns possessing a methyl group at C6 (spinosyn D-related analogs) tend to be more active and less affected by changes in the rest of the molecule.