The life cycle and seasonal phenology of the endemic geometrid Pseudocoremia suavis (Butler) is described, as well as a method for rearing the species continuously in the laboratory on cut foliage of radiata pine (Pinus radiata D.Don). Both males and females demonstrated developmental polymorphism, having either five (Type I) or six (Type II) larval instars. These two larval types did not differ significantly in the total development time (from egg hatch to adult) of around 60 days in either case.The development time and head capsule widths of the penultimate and ultimate instars of each type suggest that these two instars are equivalent in both Type I and Type II larvae. In the field, most instars were present throughout the sampling period from mid-November to mid-March, and no clear peaks in activity were observed for adult males caught on female-baited sticky traps. These results support the findings of others that this species does not have clearly synchronised generations. Catch data from femalebaited traps revealed that calling peaked in one-day old females, with a mean of c. 27% of catches, and declined steadily with age. About 99% of cumulative catches occurred by the time females were 12 days old