Table 4.

Support of selected similar-sized species with slender tarsi versus those with wide tarsi by the surface of water

Species with slender tarsiSpecies with wide tarsi
Dianous coerulescensStenus commaS. fossulatusS. junoS. providusS. similisS. solutusS. pubescens
Mean body weight (N) (N=10-12)3.83×10-5±4.1×10-62.57×10-5±3.0×10-61.89×10-5±2.7±10-63.47×10-5±5.3×10-62.39×10-5±1.3×10-62.88×10-5±2.6×10-62.73×10-5±2.4×10-63.88×10-5±2.9×10-6
Mean hind tarsus width (m) (N=10)8.00×10-5±1.2×10-64.94×10-5±1.5×10-64.06×10-5±7.3×10-74.98×10-5±1.0×10-64.62×10-5±1.3×10-61.10×10-4±2.3×10-61.11×10-4±2.0×10-61.30×10-4±1.9×10-6
Mean tarsus lengtha (m) (N=10)7.44×10-4±2.6×10-57.75×10-4±1.7×10-56.22×10-4±1.8×10-56.73×10-4±3.3×10-56.43×10-4±2.7×10-55.88×10-4±2.0×10-55.54×10-4±1.9×10-55.61×10-4±2.8×10-5
Mean apparent contact angle between tarsal ventral surface and water (degrees)147.30±2.2 (N=4)138.58±7.5 (N=5)101.77±4.9 (N=4)138.74±9.4 (N=7)138.61±11.5 (N=4)150.85±8.7 (N=6)148.48±4.1 (N=4)149.16±4.6 (N=4)
Line of contact of tarsal ventral surface with water (m)1.65×10-31.65×10-31.33×10-31.45×10-31.38×10-31.40×10-31.33×10-31.38×10-3
Buoyancy (N)3.67×10-111.46×10-117.86×10-121.29×10-111.05×10-114.81×10-115.26×10-117.30×10-11
Vertical component of surface tension (N)9.50×10-58.40×10-51.85×10-57.43×10-57.10×10-58.37×10-57.77×10-58.10×10-5
Safety coefficient7.449.812.936.428.918.718.536.26
  • The calculations were performed according to equations 1-5 in Materials and methods.

    Body parameters necessary for the calculations are also listed.

    Further assumptions: surface tension of water=0.0685 N m-1 (=mean of both the measurements reported in the Materials and methods section); density of water 1 kg m-3.

  • a Calculated as the average of fore, middle and hind tarsus length.

    Values are arithmetic means ± S.D.