6o 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I31 



body and appendages have increased in size. Churchill describes five 

 zoeal instars in Callinectes sapidiis, but his figures of the third, fourth, 

 and probably the fifth instar are said by Hopkins (1944) to be larvae 

 of some other crab. The differences, however, are slight and pertain 

 mostly to the number of setae on the appendages and spines on the 

 abdomen. In the fifth instar (D) the last abdominal segment is sepa- 

 rated from the telson and pleopods are present. About the only 



Fig. 2^. — Decapoda: Erachyura. Larval stages of Callinectes sapidiis Rathbun 

 (from Churchill, 1942). 

 A, prezoea. B, first zoea. C, second zoea. D, fifth zoea. E, megalops. 



metamorphic features of the crab zoea arc the development of the 

 dorsal and rostral spines and the adaptation of the maxillipeds for 

 swimming. 



During the zoeal stage buds of the third maxillipeds and of the 

 pereiopods appear on the thorax beneath the carapace and increase in 

 length in successive instars, but they are not seen in Churchill's 

 figures (fig. 23). It seems hardly likely that the zoea shown at D of 

 the figure could go over directly into the megalops (E). In the final 

 zoea of other crabs, sometimes called a metaaoea, the appendages be- 

 hind the second maxillipeds are well developed, as shown by Cano 



