Host Plant Mediated Differences in Papilio rutulus Lucas Larval Growth (Papilionidae)

ABSTRACT. Average development times differed significantly among the test plants and ranged from 27.9 days on Populus nigra to 61.5 days on Ligustrum japonicum. Average pupal mass differed significantly among the test plants and varied from 1330 mg on Prunus serotina to 740 mg on Fraxinus latifolia. There was a significant negative relationship between developmental time and percent larval survival and a significant positive relationship between larval survival and pupal mass. Fast larval development on a plant meant higher survival and heavier pupae. The growth rate of Papilio rutulus larvae varied from a high of 0.256 mg/day on Populus nigra to a low of 0.143 mg/day on Populus alba and 0.126 mg/day on Alnus tenuifolia. The larvae were able to extend their development time on some plants like Alnus tenuifolia and Prunus ilicifolia to produce heavier pupae. Biochemical flexibility in larval survival, developmental time and pupal mass allow P. rutulus larvae to utilize a wide variety of native and introduced plants and to colonize large areas in California with few to no native Populus or Salix hosts including urban areas with extensive plantings of ornamental plants and scattered individual apple and stone fruit trees, and the 651,000+ hectares of commercial California almond, stone fruit and apples. Selection of the host plants with the fastest development times allows P. rutulus to survive at high altitude areas in which there are otherwise too few heat units to allow their offspring to attain the pupal stage and overwinter.