Survival of eggs to third instar of late-summer and fall-breeding monarch butterflies (Danaus plexippus) and queen butterflies (Danaus gilippus) in north Texas

Introduction: Eastern migratory monarch butterflies (Danaus plexippus) have declined over 80% in recent years, but little is known about fall reproduction in the southern U.S. where monarchs may compete with queen butterflies (Danaus gilippus). Aims/methods: We provide data on the survival to third instar, associated arthropods, and phenology of fall breeding monarchs and queens in Texas. Results: Monarch and queen survival was relatively high, but varied among years. Oleander aphids (Aphis nerii), spiders, and red imported fire ants (Solenopsis invicta) had minor negative effects on survival. The abundance of monarchs and queens on the study site peaked three to four weeks before the main passage of monarchs in the area. Queens had similar phenology and exhibited a migratory pattern similar to monarchs but on a smaller scale. Discussion: Survival of fall monarchs is relatively high and potentially important for winter roost recruitment. Fall survival was not greatly affected by any particular arthropod taxon, but may be affected by precipitation. Fall reproduction is a response to available host plants and its timing enables pupae to eclose in time for migration to winter roosts. Implications for insect conservation: Management of Asclepias viridis and other native milkweeds to facilitate fall reproduction could facilitate recovery of monarchs if it buffers variable productivity further north. Management should use mowing and burn schedules that promote high quality host plants. Populations of queens should be monitored for their potential to compete with monarchs especially in response to the potential impacts of parasite resistance and climate change.