1988] 
Sierwald — Thalassius spinosissmus 
251 
from the present study indicate that Thalassius is related to Dolo- 
medes, Pisaura and Pisaurina. Lehtinen’s placement (1967) of Tha- 
lassius in the Ctenidae appears to be unjustified (see Sierwald 1987). 
The prey catching behavior of T. spinosissimus is similar to that 
of some species of Dolomedes which hunt on the water surface as 
well (Dolomedes triton: Bleckmann 1982, Bleckmann & Barth 1984, 
Bleckmann & Rovner 1984; D. aquaticus and other New Zealand 
species: Williams 1979). Rowing movements over the water surface 
have been described in D. fimbriatus by Ehlers (1939: 485); diving 
behavior is known from Dolomedes species as well (McAlister 1959: 
109). 
Acknowledgments 
The study was part of a project funded by a grant from the 
Deutscher Akademischer Austauschdienst (Bonn, Germany) and 
the Department of National Education (Pretoria, South Africa). 
The Natal Museum, and the Zoology Department of the University 
of Natal, both Pietermaritzburg, provided generous support with 
laboratory space and facilities. For advice and help I am indebted to 
Drs. J. Heeg, O. Kraus, B. Lamoral, J. Londt, J. Meester, B. Stuck- 
enberg and E. van Dijk. I thank Drs. J. Londt, G. Newlands and G. 
Stratton for helpful comments on the manuscript. 
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