Creeping Doom Conjuration
Summons a cloud of voracious insects and unleashes them on your enemies. The insect cloud will slowly home on the target, and when it strikes insects will burst outward, affecting every enemy within the area of effect. Enemies hit by the insects take 2 to 20 acid damage, plus 1 to 10 per 3 caster levels, every 2 seconds for 16 seconds. "A successful reflex save halves the damage."
Why doesn't this spell allow evasion, even it is reflex based spell?