Can Mosquitoes Have Legs in Reverse?

Wouter

During the take-off phase of a flight, mosquitoes generate pitch-up torques with their legs, wings, and wings. However, it is not known whether they generate take-off torques in reverse. The pitch-up torque produced by mosquitoes’ wings is relatively constant throughout the entire take-off maneuver. This suggests that mosquitoes use leg push-off to control the pitch-up torques.

A new study shows that a resistant strain of Anopheles gambiae is capable of remodelling its leg cuticle with enhanced deposition of chitin monomers. This may be responsible for the thicker cloak of the legs of this species. Using TEM, researchers found that the overall thickness of the leg tarsi was significantly higher in a resistant phenotype.

This study also provides novel insights into how insecticide resistance evolves. Resistance is a growing issue in Africa, where many mosquitoes are resistant to insecticides. Insecticides need to bypass the cellular and non-cellular leg barriers. The resistance of mosquitoes to insecticides appears to be related to an increase in the number of insecticide resistance genes.

The resulting force scales positively with the stroke amplitude and negatively with the deviation angle amplitude. This suggests that both the stroke angle and the deviation angle are adapted simultaneously. The implication is that the aerodynamic force vector must be changed to account for the increased body pitch angle in a blood-fed mosquito. This is a simple mechanism that is supported by the results.

In addition, a blood-fed mosquito must also generate larger aerodynamic pitch-up torques. To determine the effects of these torques on the aerodynamic fraction of the leg, the authors measured the wingbeat-average aerodynamic resultant forces. The resulting force was normalized to a standard mass of 1 mg. Interestingly, the resultant force showed a significant positive correlation with the shallow stroke amplitude.

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