Mating Behavior and Reproductive Biology of Emerald Ash Borer (Coleoptera: Buprestidae) and Two of Its Native Congeners, the Twolined Chestnut Borer and the Bronze Birch Borer

We studied the mating behavior and reproductive biology of three members of the genus Agrilus: the bronze birch borer, Agrilus anxius Gory; the twolined chestnut borer, Agrilus bilineatus (Weber); and the emerald ash borer, Agrilus planipennis Fairmaire. All three species share a highly stereotyped mating behavior. However, the copulation duration of A. planipennis was 90% longer than that of its two congeners. Female reproductive tracts of the three species were anatomically similar, as were the spermatophores. Within the spermatophores, sperm were single in A. anxius and A. bilineatus, while in A. planipennis, sperm were bundled in groups of approximately 20 in a hyaline sheath. We found that field-caught A. anxius and A. bilineatus had higher rates of female insemination than A. planipennis. In additional studies with A. planipennis and A. anxius, we found that mating duration was related to mating success, and fecundity for A. planipennis, but not for A. anxius. For both A. planipennis and A. anxius, the spermatophore was passed to the female toward the end of the copulatory period. Sperm were found in the spermatheca immediately after copulation ended in A. planipennis and 30 min after copulation ended in A. anxius. We present possible explanations for these differences.