GRANT, Jacqualine B.; Colorado State University: Ontogeny of defensive behavior and adaptive coloration in larvae of the panic moth, Saucrobotys futilalis

Many lepidopteran species have radically different coloration in early and late larval instars. This ontogenetic variation in morphology is most likely due to temporal changes in the costs and benefits associated with foraging and defensive behaviors. Larvae of the panic moth, Saucrobotys futilalis, lack cuticle pigment during most of the first three instars, which causes them to appear the same green as their host plant. The cuticle begins to produce pigmentation in the third instar and in the last two instars is an aposematic orange with black spots. Although all instars are gregarious, early larvae behave much differently than mature larvae. Cryptically-colored early larvae are patch-restricted foragers, wriggle when attacked, do not defensively regurgitate, and are extremely vulnerable to predator attack. Mature larvae employ a nomadic foraging strategy, which results in a more exposed lifestyle and concomitant enhancements in defensive strategy. This ontogenetic switch in foraging strategy corresponds with the use of regurgitation and immobility as defensive responses. I show that 1) larval color changes predictably with instar; 2) larval defensive behaviors change with instar; and 3) the intertwining of behavior and morphology are important in the development of aposematic coloration in this species. My results demonstrate the importance of detailed natural history studies in elucidating the underpinnings of certain behavioral phenomena.