282 
Psyche 
[June 
food economy of the species during periods of low stream produc- 
tivity; I commonly find nymphs and adults feeding on smaller 
nymphs of their own species. After the second instar, cannibalism 
seems to be far the most common cause of fatality among nymphs. 
Ecdysal failure and physical catastrophes (flood and drought) also 
regulate populations. Lethocerus adults, which are seasonally common 
but never abundant in Sonoran streams, may regularly take adult 
Abedus but I have observed only one instance of this. In general, 
A. herberti adults are at the pinnacle of the aquatic food chain, and, 
having reached adulthood, stand an excellent chance of surviving to 
produce or brood several clutches of eggs. 
Discussion 
The life history of Abedus herberti seems to follow closely the 
pattern reported for other genera belonging to the subfamily Belo- 
stomatinae. Allometric development of the protarsal claws closely 
relates Abedus to Belostoma, and suggests their common ancestry 
with the two clawed genera. Five instars is the number characteris- 
tic of acquatic Hemiptera (Hungerford 1920). 
Acknowledgements 
I wish to thank Dr. M. Parsons, Dr. A. S. Menke, and Dr. J. 
Alcock for review. 
Literature Cited 
Cobben, R. H. 
1968. Evolutionary trends in Heteroptera. Part I Eggs, architecture 
of the shell, gross embryology and eclosion. Center for Agricul- 
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Pp. 206-209. 
Cullen, M. J. 
1969. The biology of giant water bugs (Hemiptera: Belostomatidae) 
in Trinidad. Proc. R. Ent. Soc. Lond. (A) 44: 123-137. 
De Carlo, J. M. 
1962. Consideraciones sobre la biologia de Lethocerus mazzai De Carlo. 
Physis, 23 : 143-151. • 
Harvey, G. W. 
1906. A ferocious water-bug. Proc. Ent. Soc. Wash., 8: 72-75. 
Hungerford, H. B. 
1920. The biology and ecology of aquatic and semiaquatic Hemiptera. 
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