They examined levels of the European corn borer and corn earworm. As maize matures, DIMBOA levels and resistance to the corn borer decline. The female European corn borer moth first lays eggs in June. Several of them, including the European corn borer, are agricultural pests. The European corn borer progresses through four developmental stages. The adult European corn borer is about long with a wingspan. During the winter, the European corn borer stays in its larval stage. The Asian corn borer is most commonly found throughout Asia and Southeast Asia. The Asian corn borer goes through six instar stages while in the larval phase. European corn borer caterpillars damage corn by chewing tunnels through many parts of the plant. Female corn borer moths lay clusters of eggs on corn leaves, usually on the undersides. Additionally, the Asian corn borer has the potential to develop the insect disease muscardine. The European corn borer, one of Bt's primary targets, is also capable of developing resistance.