Dorsal anterior abdomens of late instar larvae of Trogoderma inclusum Le Conte and T. variabile Ballion were exposed to six doses from each of three lasers. The effects were followed for 183 days after lasing. Ruby (1.6–9.5 j/cm2) and neodymium (4.3–24.9 j/cm2) lasing killed the darker T. variabile larvae at lower doses than those required to kill the paler T. inclusum larvae. Dehydration through ruptured exocuticle and denatured cuticle was the main cause of death. Carbon dioxide (2.1–12.7 j/cm2) lasing killed larvae of both species at intermediate and high doses due to denaturation, degeneration of the fat body, and inhibition of moulting.

At sublethal doses, subsequent instars bore lesions which lacked exocuticle and setae. Internally, the lesions consisted of wavy cuticle and thickened, vacuolated epidermis. These lesions were reversible because they regressed with moulting. Additional setae occurred in lesions of later instars where exocuticle had been initially lacking. In terms of irradiance, mortality, penetration, and persistence of lesions, the carbon dioxide laser was the most effective, the ruby laser was intermediate, and the neodymium laser the least effective.