Acronicta insularis, the cattail caterpillar (when referring to the larva) or Henry's marsh moth (when referring to the adult), is a moth of the family Noctuidae.

It is found from coast to coast throughout the United States and southern Canada (Ontario, Quebec, New Brunswick, Nova Scotia, British Columbia, Alberta, Saskatchewan and Manitoba).

The larvae feed on Typha and Polygonum species, as well as various grasses and sedges, poplar and willow.

In 2015, the genus Simyra, along with Oxicesta and Eogena, were moved to Acronicta based on phylogenetic analysis.

[4] The MONA or Hodges number for Acronicta insularis is 9280.