[Objectives]  Larvae of Athetis lepigone (Mŏschler) damage maize seedlings when these are under wheat straw making this damage difficult to detect at an early stage. This study aims to clarify the relationship between the population dynamics of these larvae and crop damage caused by them. [Methods]  Extensive monitoring was conducted in central and southern Hebei Province between 2014 and 2016. Study plots were situated where A. lepigone damage was serious and monitoring began after corn sowing. Plots were investigated daily once larvae were found and complete datasets were obtained in Guantao county and Nandagang district. [Results]  Population growth and crop damage approximated the Peal-Reed curve. Larvae increased rapidly in abundance after they were first detected, but declined rapidly after they began to pupate. The proportion of damaged plants also increased rapidly after damage was first detected and approximated an “S”-shaped curve over time. The peak proportion of damaged plants was recorded in only 4 days. [Conclusion]  Under particular ecological and climatic conditions A. lepigone has the capacity for explosive population growth and can rapidly damage a high proportion of maize crops. This study provides a theoretical basis for the scientific control of A. lepigone.