JAMESON, ANNEMARIE. Department of Biology, University of Miami, P.O. Box 249118, Coral Gables, FL 331240-0421. - Feeding trials of Giant Swallowtail larvae on Rutaceae in south Florida.
Specialist herbivores are linked to their host plants through a
variety of mechanisms from oviposition cues, to cues to feed on the
host the larval herbivore finds itself, to non-tolerance of a host
once feeding is initiated. In order to examine the diet breadth of
the Giant Swallowtail, Papilio (=Heraclides) cresphontes, in
south Florida, I examined survival and development time of larvae to
pupation on both the host plants on which eggs were laid and of an
alternate host plant that I switched eggs to. Giant Swallowtails
range from North America through northern South America, where they
specialize on the family Rutaceae. There were three control groups
(larvae raised on their natal host plant): Casimiroa edulis,
Zanthoxylum fagara, and Z. coriaceum, hereafter referred
to CE, ZF and ZC. There were two treatment groups: ZF to CE, and ZC
to ZF. Survival in the control groups was either nearly complete (CE
and ZF) or an utter failure (ZC). In the treatment groups, survival
was complete on ZC, and nearly complete on CE. Among larvae in the
control groups, larvae raised on CE took significantly less time to
develop than that raised on ZF. When I switched eggs from ZF to
other plants, the mean number of days to develop reflected that
change. Eggs switched to CE pupated after a time intermediate to
those raised on a natal plant of ZF or CE. It is interesting to note
that the longest development time is that of larvae switched to a
palatable plant (ZF) from one they fail to accept as a host (ZC).
Additionally, while CE is exotic in Florida, its range includes other
portions of the Giant Swallowtail's range. It appears that host plant
usage in the Giant Swallowtail is genetically determined, likely as a
result of all three mechanisms.
Key words: Casimiroa edulis, diet breadth, feeding trials, Giant Swallowtail, Rutaceae, Zanthoxylum fagara