Whether Macdunnoughia crassisigna (Lepidoptera: Noctuidae) is a Long-Distance Migrant?

Macdunnoughia crassisigna (Warren) is an important polyphagous pest of bean crops and cruciferous vegetables. Whether this species is a migrant, and if so, what pattern of seasonal migration it exhibits in northern China remains unknown. The combination of searchlight trapping, ovarian dissection, and carbon isotope analysis on a small island in the center of the Bohai Strait during 2003-2013, provided direct evidence that both male and female M. crassisigna moths migrate at least 40-60 km across the sea. There was considerable annually and monthly variation in the number of M. crassisigna caught in the searchlight trap, with the vast majority (80.40 +/- 4.84 %) was trapped in the summer. The mean time from the earliest trapping within a year was 143 +/- 10 days from 2003 to 2013, with the shortest time span of 54 days in 2003 and the longest of 173 days in 2012. Carbon isotope analysis showed that 5.82 +/- 0.92 % to 17.88 +/- 8.10 % of the tested M. crassisigna moths originated from C-4 plants from May to September 2010-2013, which provides additional evidence that this species is a migrant because there are no C-4 plants on this island. The vast majority of the trapped females were virgins (86.29 +/- 1.97 % to 89.29 +/- 1.67 %) with little or no ovarian development (level 1-2, 81.06 +/- 4.98 % to 87.34 +/- 2.76 %) from May to September 2009-2013, as suggests that the onset of migration this species exhibits is initiated mainly by sexually immature individuals, which is termed the 'oogenesis-flight syndrome'. Given that large numbers of adult M. crassisigna were captured while flying up to 500 m above sea level at a site with no local populations, the findings indicate that M. crassisigna is a long-distance migrant, and the pattern of seasonal migration this species exhibits is a regular ecological behavior in northern China. Such results highlight a new route for developing sound forecasting systems of M. crassisigna.