Chirpers are immature Droyne who have not been casted.  If Droyne do not caste, they continue development, though very slowly.  Sexual differences emerge, but casteless Droyne remain small and semi-intelligent and continue to resemble immature Droyne.  Those Droyne groups which have lost the ability to caste (these are fairly common) live as primitives.  Chirpers are also psionic, so they are impossible to catch.  A chirper may occasionally befriend a human.

-IE ldr