1970] 
257 
White and Raff — Williamsonia 
Discussion — When Davis (1913) erected the genus William- 
sonia, he noted the difficulties previous investigators had had in 
assigning Williamsonia lintneri to the already established genera. 
Certain characters of wing venation in particular were quite distinct 
while others suggested affinity with the Libellulidae. The nymph 
of Williamsonia lintneri also differs from those of other corduliid 
genera and consequently gets lost in the keys of Needham and West- 
fall (1955, p. 349) and of Gloyd and Wright (1959). In general 
appearance the nymph of Williamsonia lintneri somewhat resembles 
that of Dorocordulia lepida (Hagen) ; however, it is easily distin- 
guished from that species and the nymphs of all other corduliid 
genera by the combined presence of dorsal hooks on abdominal 
segments 3 through 9 and lateral spines on abdominal segment 9 
only. 
Acknowledgements 
We especially thank Dr. Philip S. Corbet and Dr. Minter J. 
Westfall, Jr. for reading the first draft of this manuscript and 
making numerous helpful suggestions. We also thank Dr. Frank 
M. Carpenter for his encouragement and editorial comments. 
References 
Corbet, Philip S. 
1953. A terminology for the labium of larval Odonata. The Ento- 
mologist 86: 191-196. 
Davis, Wm. T. 
1913. Williamsonia, a new genus of dragonflies from North America. 
Bull. Brooklyn Ent. Soc. 8: 93-96. 
Gloyd, Leonora K. and Mike Wright 
1959. Chapter 34 in Ward and Whipple, Fresh Water Biology, W. T. 
Edmondson (Ed.), John Wiley and Sons, Inc. New York, N.Y. 
Hagen, Herman A. 
1878. Cordulia lintneri, In Selys, Secondes additions au Synopsis des 
Cordulines. Bull Acad. Belg. 45: 187-188. 
Howe, R. Heber 
1923. Williamsonia lintneri (Hagen), its history and distribution. 
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Needham, James G. and Hortense B. Heywood 
1929. A Handbook of the Dragonflies of North America, 378 pp. Chas. 
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1955. A Manual of the Dragonflies of North America, 615 pp. Univer- 
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Williamson, E. B. 
1923. A new species of Williamsonia (Odonata-Corduliinae) . Can. 
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