Not surprisingly, nutrition had a pronounced impact on beetle growth. Genitalia in poorly fed males were 7 percent shorter than in well-fed males. Wings and legs each were about 20 percent smaller. Horns, however, differed by almost 60 percent, meaning horn growth was three times as sensitive to nutrition as wings and legs, and almost nine times as sensitive as genitalia.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 340