Ophryocystis elektroscirrha sp. n., a Neogregarine Pathogen of the Monarch Butterfly Danaus plexippus (L.) and the Florida Queen Butterfly D. gilippus berenice Cramer1

SYNOPSIS. Naturally occurring populations of the monarch butterfly, Danaus plexippus (L.) and the Florida queen butterfly D. gilippus berenice Cramer were found infected with Ophryocystis elektroscirrha sp. n. This neogregarine pathogen infects the hypodermal tissue, remains in micronclear schizogony until after pupation of the host, and then rapidly completes morphogenesis in the tissue that becomes the scales of the adult butterfly. The adult thus carries the spores externally; no internal infection was detected. The pathogen is unique in the genus Ophryocystis because: other species have all been reported from the Malphigian tubules of Coleoptera; no pseudopodial attachments of schizonts to host tissue were seen; the merozoites were motile; the cystic membrane surrounding the zygote was tenuous, and the sporont developed with no apparent membrane other than the spore wall: and the spore wall appeared amber in transmitted light when morphogenesis was completed.