| Summary: | Males of the moth Utetheisa ornatrix produce
a pheromone, hydroxydanaidal, contained in two brush-like
organs, the coremata, which they evert during courtship.
Hydroxydanaidal is derived chemically by the males from
pyrrolizidine alkaloids that they sequester from their larval
food plants. It had been shown previously that the amount
of hydroxydanaidal in the coremata correlates positively
with a number of male parameters that are a measure of
the male's 'worth.' Hydroxydanaidal could thus be used
by the female as a basis for discrimination in courtship.
Experiments carried out with virgin Utetheisa had shown
that females do indeed mate selectively with males of
high corematal hydroxydanaidal content, thereby accruing
the multiple benefits that are the consequence of such selectivity.
Unresolved was the question whether corematal
hydroxydanaidal could still provide a basis for female
appraisal of suitors when these had previously mated. Given
the proven promiscuity of the female, male Utetheisa
could be expected to be promiscuous as well. Evidence we
present here shows that field-collected males, which could be
expected to be mostly non-virginal, are of reduced acceptability
to females. They are also, on average, in possession
of lower quantities of hydroxydanaidal, explaining possibly
why they should be held in lesser regard. At low levels, however,
hydroxydanaidal does not lend itself for precise assessment
of male worth, because as we show herein, at
such levels, the compound does not correlate with any of the
criteria of male quality (male size, spermatophore mass,
male pyrrolizidine alkaloid content, amount of pyrrolizidine
alkaloid transmitted to the female). Males that have mated
beforehand are therefore likely not to be classed into subcategories
by the females, but simply as belonging to one category
of 'less desirables'. The significance of these findings to our
understanding of the mating strategy of Utetheisa is discussed.
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