Comparative life stages and behavioral characteristics of two Spilomelinae moths with overlapping feeding periods on Azolla spp., in the northern Iran

Diasemiopsis ramburialis and Nomophila noctuella are moths from Spilomelinae (Lepidoptera: Crambidae) with an overlapping feeding period on Azolla spp. in northern Iran. Due to some morphological similarities, immature stages often lead to confusion. A five-year study conducted in laboratory and natural environments revealed that, despite these morphological similarities, distinct characteristics in both morphology and behavior can facilitate their primary identification in the field. Diasemiopsis ramburialis eggs, and first instar larvae are opaque to pale orange, while those of N. noctuella are pale to creamy. Additionally, the last instar larvae of D. ramburialis feature orange head capsules with smaller body sizes and tend to pupate near the feeding site. In contrast, Nomophila noctuella’s last instar larvae have black head capsules, larger body sizes, and pupate at a distance from the feeding site. Both species exhibit shelter-building behavior, binding Azolla spp. leaves together using silken webs to create protective enclosures. However, D. ramburialis larvae construct more robust shelters and produce more webs. They primarily remain within these shelters and navigate through web-formed corridors. On the other hand, N. noctuella larvae prefer to move along the feeding site margins within corridors formed by bound-up leaves and display a more wandering behavior. The study’s findings indicate that Azolla spp. serves as the primary host plant for D. ramburialis, while N. noctuella appears to choose its host plants randomly.