| The ability of insects to pick up pheromone signals from air flow is vital to their success in reproduction. This ability depends largely on the antennal morphology and the flow patterns around antennae. In this study, some fluid mechanical properties of the flow around antennae of Bombyx mori and Manduca sexta were examined. The transmissivity of the porous silkmoth antennae was determined employing the terminal velocity measurement. The flow patterns around the antennae of B. mori and M. sexta were examined by flow visualization. Study on molecular diffusion in the vicinity of antennal sensilla was also performed by physical modeling and numerical simulation.; The transmissivity, or fraction of air flow through the antennae, of silkmoth antennae ranged from about 10% to about 27%. The magnitude of transmissivity was independent of flow velocity in the range from 0.1 to 1 m/s. A pair of vortices formed behind B. mori antennae for Reynolds numbers between 40 and 70, but not behind those of M. sexta for Reynolds numbers between 15 and 26. The flow through the antennae could be detected downstream of the B. mori antennae. No apparent turbulence was observed downstream of M. sexta antennae. The diffusion experiments partially agreed to the results yielded from the computer simulation. Tentative predictions were made for the situation of molecular diffusion around sensilla. |
