The influence of light level on the expression of resistance in Solanum berthaultii Hawkes (accessions PI 473331 and PI 473334) to the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), was studied by exposing plants to two levels of photosynthetically active radiation: 272 ± 37 μE/m2 per sec and 1025 ± 150 μE/m2 per sec. Over 26 days, shading generally reduced densities of type A and B glandular trichomes, volume of trichome exudate, and phenolic oxidation activity of type A trichomes. In both light regimes, larvae reared on S. tuberosum L. were heavier, developed more rapidly, and had greater survival than those reared on S. berthaultii. Similarly, females reared on S. tuberosum were heavier and produced 10- to 20-fold more egg masses and 68 to 472 times more eggs than those reared on S. berthaultii grown at the same light level. Light level did not affect larval weight, developmental time, survival, adult weight, or fecundity of CPB on either host plant species.