SWIMMING ABILITY OF NOTONECTIDAE 
(HEMIPTERA) 
By Steven H. Gittelman* 
Biological Sciences Group, University of Connecticut 
Storrs, Conn. 06268 
In an earlier paper, I (Gittelman 1974) studied adaptations 
of fore-leg size and hind-leg lever systems for prey capture and 
swimming. Presently, the ability of 4 species of Connecticut 
Notonecta to swim against a current is studied as a test of predic- 
tions generated by this earlier work. 
To study leg mechanics we will schematically represent a leg 
or leg segment (femur, tibia, and tarsus) as a simple lever with 
the fulcrum at the articulation between it and the structure on 
which it articulates. Force (F m ) is applied at the muscle insertions 
at the proximal end and the lever arm is the distance (Rf) from 
the fulcrum to where the force is applied, the resultant force 
(F r ) is the force generated by the lever to do work (press against 
water while swimming) at any given distance (R 2 ) away from 
the fulcrum and is related to the muscular force as follows: 
F = — F 
^ R: 
The ratio R 1 /R 2 corresponds to the mechanical advantage. 
Smith and Savage (1956) compared the mechanical advantage 
of muscles of the forelegs of the horse ( Equus ) and a fossorial 
armadillo ( Dasvpus ). They concluded that if the Ri R ratio is 
large, leg movement will be powerful though slow. If the ratio 
is small, it will be fast but weak. 
Gittelman (1974) measured R 1 /R 2 ratios in 10 species of North 
American Notonectidae in the genera Notonecta (4 spp.), Buenoa 
(4 spp.) and Martarega (2 spp.). The total length of the hind-leg 
(R 2 ) from the trochanter-coxa articulation to the distal tip of 
the tarsi (not including the tarsal claw), and the lever arm (Ri), 
the distance from the ventral trochanter-coxa articulation to 
the proximal end of the trochanter at the insertion of the depres- 
*Present address: Box 229, Jericho, N.Y., 11753. 
Manuscript received by the editor October 30, 1976. 
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