Parasitoids are generally accepted as any arthropod whose "larvae feed exclusively on the body of another arthropod, its host, killing it" (Godfray, 1994). Recent studies have begun to show that parasites do not always kill their hosts-possibly due to host behavior. The purpose of this study was to determine if gypsy moth larvae parasitized by a wasp behave differently than unparasitized larvae in regards to activity level, preferences in light, temperature, and food, temperature tolerance and food consumption (weight gain). When exercised for one minute, parasitized larvae (x = 21.88 cm), traveled further than unparasitized larvae (x = 6.19 cm) (p < 0.000049). When given the choice of light or darkness in multiple trials, 44.3% of parasitized larvae preferred light, compared to 87.7% of unparasitized larvae (p < 0.00078). When given the choice of warm or cold temperatures, only 11% of parasitized larvae preferred warmth, compared to 86.6% of unparasitized larvae (p < 0.0003). Also, when raised in cold temperatures, parasitoid exposed larvae survived to adulthood more often than unparasitized larvae (p < 0.0120). When given the choice of regular (control) or diets containing hemlock (Conium maculatum), parasitized larvae chose the hemlock diet more often than the unparasitized larvae (p < 0.0051), which chose the control diet (p < 0.0141). Finally, when raised on a hemlock diet, unparasitized larvae experienced less weight gain than when raised on a control diet (p < 0.00027), compared to parasitoid exposed larvae that gained about the same amount of weight when raised on either diet. Ultimately, further experimentation using both L. dispar and G. flavicoxis could be used to strengthen the behavioral relationships seen in this study and to provide more insight into the relationship of altered behavior and host fitness.