Morphological Changes of <i>Aedes aegypti</i> Larvae After Exposure to 0.02 ppm Temefos

Introduction: Ae. aegypti is the primary vector of arbovirus diseases such as Dengue Fever (DHF), Zika, and Chikungunya. The use of the larvicide temephos remains the primary vector control strategy. Still, the emergence of resistance in several regions requires an assessment of its effectiveness and impact on larval morphology. Objective: To determine the morphology of Ae. aegypti larvae after exposure to temephos at a concentration of 0.02 ppm. Methods: Larval sampling was conducted in three dengue-endemic areas: Semarang City, Jepara Regency, and Brebes Regency. The specimens used for observation were third-instar larvae. Post-exposure to temephos at a concentration of 0.02 ppm was repeated three times, with 20 larvae exposed at each replication. Morphological observations were made on larvae that died after 24 hours of holding using a stereomicroscope with 10x and 40x objective lenses. Results: All larvae died, placing them in the susceptible category. Morphological changes were found throughout the larvae’s bodies. The head showed darkening, shrinkage, and loss of the visual margin of the eyes. The thorax appeared smaller, with the boundaries between segments disappearing and black spots appearing. The abdomen darkened, especially in segments 4–5. The body stiffened and became curved. The siphon and anal segments showed swelling and black spots, indicating tissue damage and an immune response in the form of melanization. Conclusion: Temephos at 0.02 ppm was still highly effective against Ae. aegypti larvae and caused morphological disturbances reflecting physiological stress and immune response activation.