Aphthona nigriscutis Foudras is an insect commonly used for the biological control of leafy spurge (Euphorbia esula L.) in the United States and Canada. The establishment success of A. nigriscutis has been variable, and when compared to a similar species, Aphthona lacertosa Rosenhauer, has slower rates of population growth and is considered less effective at controlling leafy spurge. Adult populations of A. nigriscutis have been observed to be highly female-biased, ranging from 79 to near 100% female, while adult populations of other Aphthona flea beetle species have sex ratios that are approximately equal (ranging from 41 to 62% female). It was hypothesized that the highly biased sex ratios may reduce female mating success, due to the rarity of males, which could result in establishment failure of introduced populations or slowed growth of established populations of A. nigriscutis. The results of this study indicate that A. nigriscutis populations do have highly female-biased sex ratios, but there was no significant difference in female mating success between A. nigriscutis (biased) and A. lacertosa (unbiased). Hence, female-biased sex ratios do not appear to lead to decreased population growth rates via reduced female mating success in established A. nigriscutis populations.
Species 1: Coleoptera Chrysomelidae Aphthona nigriscutis (Black dot flea beetle)
Species 2: Coleoptera Chrysomelidae Aphthona lacertosa
Keywords: leafy spurge, flea beetle
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