Heliothis viriplaca (Hüfnagel) (Lepidoptera: Noctuidae) is an important polyphagous pest of beans, cotton, maize, and alfalfa worldwide. H. viriplaca is a long-distance migrant, and if so, what pattern of seasonal migration this species exhibits in northern China remains unknown. In this study, in order to determine the seasonal migration of H. viriplaca in northern China, the combination of searchlight trapping and ovarian dissection was carried out on an isolated small island in the center of the Bohai Strait during 2003–2014. The results confirmed that H. viriplaca undertakes long-distance migration on the prevailing winds of the East Asian monsoon airflows. This species exhibited a regular pattern of seasonal migration across the sea from May to October, but there was considerable yearly and monthly variation in the trapped numbers, with the majority being trapped in summer (67.99 ± 6.54%). The mean period when migration was detectable at the island was 116.5 ± 5.6 days from 2003 to 2014, with the shortest time span of 74 days in 2013 and the longest of 144 days in 2005. Trapped females in May and June showed a relatively higher mating rates and some degree of ovarian development when compared with July, August and September, suggesting the migration of this species is not completely bound by the ‘oogenesis-flight syndrome’. These findings will be helpful to improve the forecasting system and managing strategies of H. viriplaca.

Marked seasonal reproduction is a widespread phenomenon in seaweeds in temperate waters strongly influenced by seasonal variations. In the Baltic Sea, however, the perennial brown alga Fucus vesiculosus exhibits two periods of reproduction: early summer (May–June) or late autumn (September–November). In this study, we compared the geographical distribution, the reproductive biology and the recruitment success for F. vesiculosus that reproduce during either of these two periods on the east coast of Sweden. Both monocultures and mixed populations of summer- and autumn-reproducing F. vesiculosus occurred along the mainland coast from the southern parts of the Stockholm archipelago to the southernmost part of Sweden. F. vesiculosus reproduced only during summer around the coasts of the large islands of Öland and Gotland. After reproduction, in July and January respectively, plants that reproduced in summer abscised their receptacles and part of their branches, while plants reproducing in autumn abscised only their receptacles. In laboratory experiments, short-day treatments (light:dark 8:16 h) were shown to initiate receptacles in summer-reproducing plants, whereas plants reproducing in autumn initiated receptacles independently of short- or long-day (light:dark 16:8 h) treatment. Plants reproducing during summer produced more eggs (21·0×104 eggs/g−1 frond mass) of smaller size (0·067 mm) than plants reproducing during autumn (8·9×104 eggs/g−1 frond mass, egg size 0·070 mm). However, recruitment success in the field was similar irrespective of the period of reproduction. The differences in the photoperiodic response, the differences in reproductive output and egg size between summer and autumn plants, and the observation that a single individual kept the same pattern of reproduction over a period of at least three reproductive seasons, may indicate that the two strategies of reproduction in F. vesiculosus are expressions of two distinct genotypes.