Urban occurrence, flight performance, and starvation tolerance of the tortoise beetle Laccoptera nepalensis in Tokyo, Japan

In urban landscapes, patchily distributed host plants may constrain the occurrence and persistence of herbivorous insects. The tortoise beetle Laccoptera nepalensis , a herbivore of Convolvulaceae plants including sweet potato, Ipomoea batatas , has expanded its distribution in Japan since the late 20th century. The objective of this study was to determine the occurrence of L. nepalensis in Convolvulaceae patches in the field and obtain basic information on adult flight performance and starvation tolerance under laboratory conditions. A three-month line-census survey in Hachioji City, Tokyo, recorded 144 Convolvulaceae patches, of which six were occupied by adults. Eggs and larvae were also observed, suggesting reproduction in some scattered patches. In flight-mill experiments, flight was observed in 5 of 10 individuals in 2023 and 6 of 16 in 2024. Mean flight distance among flying individuals was 11.66 ± 19.71 m in 2023 and 4.57 ± 3.95 m in 2024, with a maximum of 50.7 m. Starvation experiments showed median survival times of 3–7 days without food or water and 8–11 days when water was provided, depending on temperature. Given the limited sample size, these results should be interpreted as preliminary trends. Overall, scattered host-plant patches may provide local habitats for L. nepalensis , and adults may tolerate temporary food deprivation. The sporadic field occurrence pattern, together with limited flight activity under flight-mill conditions, is also consistent with the possibility that human-mediated dispersal contributes to some urban occurrences.