Water strider's(Aquarius paludum)(Heteroptera: Gerridae) stroke force on the water

摘要

We measured the force of free-swimming water striders(Aquarius paludum)using a hair attached to their back and a 3D force sensor.We observed with a high-speed video camera,and chose only those measurements in which the stroke was just completed when the signal was transmitted to the sensor.The error calculated by comparing force and geometrical derived data,was estimated as 13%.Females in average were stronger(1.32 mN)than males(0.87 mN),however the ratio force/weight was not significantly different.Compared to other lighter species' data available in literature A.paludum seems to be stronger,but the ratio force/weight is actually lower.A.paludum applies about 0.3-0.4 mN/cm with its mid-legs thus avoiding to penetrate the surface tension layer while propelling rapidly over the water.