Question mark butterfly

The Question mark butterfly (Polygonia interrogationis) is a member of the Nymphalidae family within the order Lepidoptera. While primarily observed in ecological research, it is classified as a sporadic agricultural pest, specifically impacting plants within the Cannabaceae and Ulmaceae families.

The larvae of this species feed on a variety of plants, most notably common hops (Humulus lupulus), stinging nettle, elm, and hackberry. In commercial hop yards, an outbreak of these larvae can result in significant defoliation, which hampers the plant's ability to produce viable cones and impacts commercial yield.

The biological cycle consists of complete metamorphosis: egg, larva (caterpillar), pupa (chrysalis), and adult (imago). The adults are known for their distinct wing shape, which mimics withered leaves. Larvae typically go through five instars before pupating on the host plant, and the species often overwinters in the adult stage.

Damage caused by this pest is strictly foliar. Caterpillars consume leaf tissue, creating irregular holes and eventually skeletonizing the leaves. This reduction in photosynthetic tissue can stress the plant, making it more susceptible to environmental factors and disease, though economic damage is usually limited to specific, localized high-pressure infestations.

Effective management strategies rely on integrated pest management (IPM) practices. Growers should focus on early detection through visual scouting of the undersides of leaves. If chemical intervention is required, selective bio-insecticides or microbial products, such as those containing Bacillus thuringiensis, are recommended to minimize impact on beneficial predatory insects and pollinators.