The longevity and fecundity of adult Phoracantha recurva and Phoracantha semipunctata were strongly affected by diet. Female P. recurva fed a diet of Eucalyptus pollen and sucrose solution lived 34–56% longer than females fed diets containing other types of pollen, ground dog chow, or sucrose solution alone. Diet had no significant effect on longevity of P. recurva males. Similarly, longevities of P. semipunctata females were increased 48–71% on the Eucalyptus pollen diet compared with the other diets. Male P. semipunctata also lived longer on the Eucalyptus pollen diet than most of the other diets. Fecundity was dramatically affected by diet, with P. recurva females fed the Eucalyptus pollen diet laying ≈4–8 times more eggs than females on the other diets. Eucalyptus pollen also increased the fecundity of P. semipunctata females ≈3–5-fold. Diet resulted in only minor effects on egg size and percent egg hatch for both beetle species.