Illuminating Apocephalus Coquillett (Diptera: Phoridae) parasitoid biology

Association with different hosts can lead to reproductive isolation and speciation for insects. The phorid fly, Apocephalus antennatus Malloch, is classified as a single, widely dispersed, and highly generalist species that is known to parasitize many different genera of fireflies (Lampyridae). However, when other putatively generalist Apocephalus Coquillett have been analyzed with genetic markers they have proved to consist of several cryptic specialist species, each with a more limited host range. To test for hidden diversity related to host association in this widespread phorid species, I collected parasitized Lampyridae species from Costa Rica and across the eastern half of North America from May-August 2024. I extracted DNA and amplified a single mitochondrial gene and a single nuclear gene. I then sequenced the genes with an Oxford Nanopore MinION and analyzed genetic sequences alongside host associations and morphology to delimit putative species. My results do not support host associated differences in Apocephalus antennatus in North America. Evidence instead suggests a single species using several different firefly hosts, both nocturnal and diurnal. Thus, A. antennatus appears unusual among other Phoridae in being able to attack multiple different host species of several niches. This finding is an important step in understanding why host-associated differentiation (HAD) appears in certain phorid species and does not in others. I also report previously unknown occurrences of superparasitism in Apocephalus and demonstrate the efficacy of nanopore sequencing in identifying hosts of phorid parasites using only DNA extracted from pupal or adult phorids.