STUDIES ON LAKVAE OF CRABS OF THE FAMILY 



GRAPSIDAE. 



By O. W. Hyman, 



Of tile College of Medicine, University of Tennessee. 



INTRODUCTION. 



The material on which the original descriptions and drawings 

 of this paper are based was collected at Beaufort, N. C, during the 

 summers from 1916 to 1922. The egg-laden females were kept in 

 crystallization dishes until their eggs hatched. The young zoeas 

 were then drawn with the aid of a camera lucida. They were kept 

 under observation until they died within a few days. The writer 

 acknowledges his indebtedness to Dr. Waldo L. Schmitt, of the 

 United States National Museum, for his generous help in preparing 

 the material for publication. 



THE GRAPSID ZOEA. 



Tlie only zoeas of this family that have been described thus far 

 are remarkably uniform in structure.^ A zoea of Cyclograpsus is 

 mentioned by Bate and Power but neither a description nor a figure 

 is given. A young form is said to have been described by Cavolini 

 but the writer has not been able to consult the paper. The zoeas 

 referred to below are those of ^esarma^ Planes., and Pachygrapsius. 

 These are characterised by the absence of the lateral spines of the 

 carapace and the equal lengths of the antennae and frontal spine. 

 They are very similar to the zoeas of the Ocypodidae from which 

 they may be distinguished by the comparative length of the antennae. 

 These are only two thirds as long as the rostral spine in the 

 Ocypodidae. 



1 Cano describes zoeas that are assigned to Plagusia^ to EucMrograpsus, and to PUvruea 

 {Nautilograpsus) . He did not secure those of Plagusia or Euohirograpnus directly from 

 the femaJe and is somewhat doubtful in assigning them. His figures of Planes differ so 

 entirely from those of the writer that the two can not be referred to the same species — 

 probably not to the same genus. As the writer secured his zoeas by hatching frcm a 

 single female in solitary confinement there can be no doubt that they are in truth the 

 larvae of Planes. 



The larvae described by Cano for Plagusia, Euchirograpsus, and Planes resemble each 

 other closely in the structure of the telson. Those of Euchirograpsus and Planes possess 

 well developed lateral spines on the carapace. The larva assigned to Plagusia does not 

 possess carapace spines. It is highly probable that these larvae should be assigned to 

 another family altogether. 



No. 2523. — Proceedings U. S. National Museum, Vol. 65, Art. 10. 



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