Two unexplained phenomena are found in Riptortus pedestris (Fabricius) (Hemiptera: Alydidae): the first is that it tends to enter reproductive diapause much earlier in the season and to occur on host plants until late fall before finding hibernation site. The second is that they emerge in early spring when primary food sources such as leguminous plants are unavailable. To understand these phenological trends, the reproductive seasonality of both field-collected and laboratory-reared R. pedestris were compared under conditions of with/without food or access to mates. Females collected in spring or fall produced very few eggs in laboratory. But, when food sources were provided, all the bugs produced more eggs. Eggs also hatched normally except those produced by the females collected in fall. This indicates that females collected in the spring were already mated while those collected in the fall were not, most likely because they were in reproductive diapause. Similarly, when food was provided, all laboratory-reared bugs produced eggs, regardless of diapause status, with longer preoviposition period in diapausing bugs which might be due to the termination of reproductive diapause, but only eggs from mated females hatched. In conclusion, while spring reproduction (oviposition and egg hatch) of R. pedestris can occur in the presence of food resources, any lack of food can be limiting factor impeding these activities. In fall, reproduction is greatly reduced even when food resources are available, and under these conditions failure of females to become mated, due to reproductive diapause, is likely the limiting factor.