Antennal morphological differences between Alate and Apterous morphs of Semiaphis heraclei (Hemiptera: Aphididae).

Aphids exhibit wing dimorphism: apterous morphs remain on hosts to sustain reproduction, while alates facilitate colonization of new habitats. The success of alates relies on antennal sensilla mediating olfactory cues for host location, yet such adaptations remain uncharacterized in Semiaphis heraclei (Takahashi). In this study, differences in antennal morphology between morphs were compared by scanning electron microscopy. Alates had significantly longer antennae than apterous morphs due to flagellar elongation and also uniquely had secondary rhinaria, densely distributed across flagellomeres I to III. They also had significantly larger primary rhinaria, but trichoid and campaniform sensilla showed no differences between morphs. These results indicate that antennal dimorphism underlies ecological specialization in S. heraclei: alates display enhanced sensory traits likely facilitating host detection and dispersal, while apterous morphs retain a conservative morphology. This study provides the first detailed characterization of antennal sensilla in the parthenogenetic alate and apterous morphs of S. heraclei. The morph-specific sensory adaptations we identified, particularly in olfactory sensilla, establish a morphological basis for future research aimed at developing olfaction-based pest management strategies.