Tiny pool protects flower buds.

Rare flower structures--tiny cups that keep flower buds submerged in their own water baths--can protect the blooms from marauding moths, say researchers.

One species with these cups, Chrysothemis friedrichsthaliana, grows along riverbanks in Central and South America, says Jane E. Carlson of Louisiana State University in Baton Rouge. A relative of African violets, the plant has hairy leaves and orange, tubular flowers.

As a flower develops, a yellow-green cup, or calyx, forms around the bud. Calyx hairs secrete liquid for 2 to 3 weeks as the bud matures.

To see whether and how the system protects buds, Carlson visited Chrysothemis patches daily in Costa Rica and drained some calyxes. The hairs can refill a calyx in 24 hours.

One in three buds failed to develop in calyxes, whether or not she drained them. She concluded that the calyxes' main role isn't in moistening buds.

Drainage did affect attacks from alucitid moths, says Carlson. Emptying calyxes doubled the chance that a moth would inject an egg into the bud. The moth larvae destroy floral sex organs inside. The petals of affected flowers open normally but show no working parts, only a rice-grain-size moth larva.

Instead of the usual four wings, these alucitid moths have arrays of featherlike plumes. Carlson speculates that the wings' fragility prevents the insects from maneuvering well in water.

She and her Louisiana State colleague Kyle Harms describe the experiment online in Biology Letters.