We present a genome assembly from an individual male Apamea monoglypha (the Dark Arches, Arthropoda; Insecta; Lepidoptera; Noctuidae). The genome sequence is 576 megabases in span. Most of the assembly is scaffolded into 31 chromosomal pseudomolecules, including the assembled Z sex chromosome. The mitochondrial genome has also been assembled and is 16.5 kilobases in length. Gene annotation of this assembly on Ensembl has identified 17,963 protein coding genes.