In species of many taxa, males alter their investment in ejaculates depending on perceived levels of male–male competition and female mating history/age. Males of the tettigoniid Acanthoplus discoidalis produce a large sperm ampulla and associated spermatophylax, resulting in a long refractory period for males. Female A. discoidalis mate once before laying eggs, and then mate and lay eggs in a random order. The males, therefore, only have a high confidence of paternity when mating with virgins. Male A. discoidalis were studied to determine if they alter their investment in sperm count, spermatophylax mass and water content of spermatophylaces when mating with virgin and non-virgin females. No difference in investment in any spermatophore characteristics between virgins and non-virgins was found, but males do reject non-virgins more often, preferring to transfer spermatophores to virgin females. Males seem to prefer females of a lower mass, where higher mass may reflect increasing female age (and hence likelihood of previous matings) through advanced development of eggs. Outright rejection, rather than changes in spermatophore investment may be because of constraints in tailoring large spermatophores that develop over relatively long periods of time between matings.
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