The leaves of blackbead have four leaflets, a pair at each end of a branched midrib. The pinkish powder-puff 'flower' is an inflorescence—a spherical head of tiny flowers with extravagant stamens. The 'flowers' are fragrant and give rise to a pod. When ripe, the pod twists and dehisces (splits) revealing shiny black seeds partially covered by a bright red aril. The seeds were strung as beads for necklaces hence the common name.
Blackbead is a host plant for the large orange sulfur (Phoebis agarithe maxima), a year-round butterfly of South Florida and the Keys. The shrub also plays sole host to a small wasp (Tanaostigmodes pithecellobiae) which oviposits within the leaflet tissues causing a gall to form.
One would think that a wasp larva developing inside a gall would be safe, but Carl Weekley discovered a gall miner, a microlepidopteran (very small butterfly), that bores into the gall, consumes both the gall and developing wasp, and uses the hollowed-out gall as a place to pupate.
(Compiled from: "The Natural History of Tanaostigmodes pithecellobiae (Hymenoptera: Tanaostigmatidae), A Gall-Maker on Blackbead (Pithecellobium keyense )", Carl Weekley, Florida Entomologist, Vol. 83, No 1, March 2000; Florida's Fabulous Butterflies, Thomas C. Emmel and Brian Kenney, World Publications, 3rd Ed. 1999; and Atlas of Florida Vascular Plants, Wunderlin, R. P., and B. F. Hansen. 2004. [S. M. Landry and K. N. Campbell (application development), Florida Center for Community Design and Research.] Institute for Systematic Botany, University of South Florida, Tampa..)
