Melanism in the oriental armyworm Mythimna separata (Walker) is characterized by a black color in adults instead of the normal body color of off-white. Because inheritance of melanism in this moth follows Mendel's law, with the melanic allele (t) recessive to the normal allele (T) at a single autosomal locus, a backcrossing procedure was used to develop near isogenic lines (NILs) for melanic (NILs-tt) and typical forms (NILs-TT) of this moth. Melanic males (tt) and typical females (TT) were crossed in the laboratory, their progeny (F(1)) were interbred, and F(2) melanic males were backcrossed to typical female offspring of the parallel line. This cycle was repeated five times to create NILs for melanic and typical forms of this moth. The effects of the melanic allele on relative fitness were evaluated in terms of developmental and reproductive characteristics. Life tables of the NILs were constructed to determine net reproductive rate (R(0)). Results indicated that NILs-tt possessed apparent developmental and reproductive advantages, including shorter immature development time, higher larval and pupal survival, a shorter adult preoviposition period, and more eggs laid per female compared with the NILs-TT.

The plant bug, Adelphocoris fasciaticollis, has begun to resurge and become a key pest for cotton and alfalfa in northern China, along with the widespread cultivation of Bt cotton. To control this plant bug without pesticides, we attempted to develop a new approach by utilizing sex pheromone. The sex pheromone components from the whole‐body extracts were analysed by GC‐MS and gas chromatography–electroantennogram detector analysis (GC‐EAD). (E)‐4‐Oxo‐2‐hexenal and hexyl butyrate, identified as the major components in the extracts of female bugs, elicited strong EAD responses. Field tests indicated that either (E)‐4‐oxo‐2‐hexenal or hexyl butyrate attracted few A. fasciaticollis males and was significantly less active than virgin females and the binary blend. Their ratio was optimized to be 1 : 11. Our results could expand acknowledge of the pheromone of mirids and provide novel approaches to monitor and control this plant bug without pesticides.

Genetic diversity within and among three wild-type natural populations and one melanic laboratory population of Mythimna separata (Walker) (Lepidoptera: Noctuidae) were evaluated using amplified fragment length polymorphism (AFLP) analysis. Although extensive genetic diversity occurs among individuals from different geographic populations (P = 54.5%, h = 0.209, I = 0.305), the majority of the genetic diversity is within populations and not between populations (G(ST) = 0.172), indicating high gene flow (N(M) = 2.403) and suggesting that M. separata in northern China are a part of a single large metapopulation. Genetic diversity in the natural populations was significantly higher than that in the melanic laboratory population (with P = 43.4% versus P = 25.9%, h = 0.173 versus h = 0.086, and I = 0.251 versus I = 0.127), suggesting that the melanic laboratory population is narrowly genetic-based and genetically uniform. Genetic similarities based on AFLP data were calculated, and cluster analysis was preformed to graphically display groupings between individuals and populations. Individuals from the same region were not grouped together in cluster analysis of three natural populations, whereas melanic individuals from laboratory population were grouped together very well. Four subpopulations were clustered into two broad groups. Melanic laboratory population became a single group, which had apparent differentiation from the other group in which three natural subpopulations were included. These results indicated that although high genetic variability existed among the individuals of natural populations, there was little genetic differentiation among three geographic populations that could be explained by the effects of the long distance migration of the oriental armyworm in China enhanced the level of gene flow. Influences of migration on the genetic polymorphism and differentiations that make a significant contribution to evolution in this insect are reviewed.