Sibling caterpillars of this butterfly species in Venezuela form a dense, radiating circular patch on the leaves where they feed. I have talked to one lepidopterist who has even observed these caterpillars swimming together as a group! This collective social behavior can confer several advantages, including protection from enemies and cooperative foraging. However, almost no strategy is likely to be 100% effective, especially in diverse tropical rain forests where extreme niche partitioning occurs. Careful inspection of the photograph shows tiny phorid flies, bloated from sucking the caterpillars� juices. These flies are not deterred by the caterpillars� defense strategy, but rather use it to their advantage to increase their host�s detectability. Host-parasite co-evolution has led to the coexistence of countless numbers of species.