I know of no insects that are predatory to irises and lay their eggs on the fans. My suspicion is that the fans were in the right location with the right shelter from the sun and/or rain.
The Orthacheta Bud Fly does hatch into larvae that bores into the buds to eat the pollen inside, but they hatch at bud time to do their evil. They do prefer Siberians, then Louisianans, but others at times also. Their eggs are deposited on the bud, near the tip. So this one is eliminated as the culprit.
Iris borer eggs are laid on the stalks and leaves and overwinter, often on the dead or decaying leaf residue near the ground, so if this cluster is on a newer leaf that one is also eliminated.
