Life stages of the non-native Ommatoiulus moreleti (Lucas, 1860) (Julida, Julidae) in Australian small grain systems

The Portuguese millipede, Ommatoiulus moreleti (Lucas, 1860), is increasingly a pest of grains crops in Australian agricultural ecosystems. With the rapid uptake of minimum-tillage practices, habitat quality has been enhanced for several species of soil dwelling invertebrates, in particular O. moreleti. To understand the population dynamics of O. moreleti in Australian grains crops, populations were sampled at multiple sites for more than 2 years using pitfall traps and cardboard roll traps. Specimens were dissected to investigate reproductive status and developmental stage. Millipede trapping rates varied between sites and across the year, and tended to be lower when soil water content (m³/m³) was high. Both sexes were active year round, however females were relatively more abundant when ground temperatures were higher. Males in a copulatory state and females with mature eggs were collected year round although females lacking mature eggs were more common when ground temperatures were higher and the soil was drier, and female egg load was higher under cooler conditions. Females at a stadium 9 or later carried mature eggs and copulatory males tended to be from stadium 8 or later. Different developmental stages could be recovered at all times of the year. These findings indicate persistent populations of O. moreleti across fields throughout the year, with a key breeding period in autumn but likely opportunistic breeding all year. Control of millipedes will need to focus on increasing the impact of biological agents, decreasing suitable habitat for millipede breeding and intensive control at susceptible crop periods.