Lack of physiological improvement in performance of Callosamia promethea larvae on local host plant favorites.

As a species, the promethea silkmoth, Callosamia promethea (Saturniidae: Lepidoptera) exhibits a wide host range on 6-10 families of plants, although specific populations are known to have local foodplant favorites. We tested the hypothesis that larvae from a particular host plant lineage would show physiological adaptations to this host compared with larvae from other host plant lineages. We found no evidence that larval survival and growth was any better for larvae fed the natural plant of the parental population than for larvae from other host lineages. These natural host lineages include: black cherry (Prunus serotina Ehrh.), tuliptree (Liriodendron tulipifera L.), sassafras (Sassafras albidum (Nutt.) Nees) and spicebush (Lindera benzoin (L.) Blume). The only apparent manifestation of physiological specialization was the inability of tuliptree lineages of C. promethea to survive on paper birch (Betula papyrifera Marsh), although this may reflect the geographical pattern of adaptation to birch, rather than a negative correlation with adaptation to tuliptree. These results suggest that for C. promethea larvae, growth performance and survival is primarily influenced by plant nutritional quality, rather than physiological adaptations to the locally preferred host plant.