Shown are the results of a clustering analysis of thoracic horn-abdomen arrays for large, horned males (H), small, sneaker males (S) and females (F). Genes included in the analysis were significantly differentially expressed (P < 0.05) at least two-fold between tissues (|M| >1) in at least one treatment category (H, S, or F) We identified two clusters of genes with biased expression in the developing thoracic horn epidermis of horned males. Bootstrapping is 100%.