66 



NATURAL HISTORY OF ARTHROPODS. 



greatly condensed. There are two 

 types of development, one passing 

 through the forms which were for- 

 merly considered as adult, and de- 

 scribed as Erichthus and tiquiller- 

 ichthus, the others through an 

 Alima stage, with the probabilities 

 that the former represents the larva 

 of Gonodactylus, the latter certainly 

 that of Squilla. In the youngest 

 known Erichthus type we have 

 both stalked eyes and a single 

 median ocellus, while the first ten 

 pairs of appendages are developed, 

 the sixth to tenth being biflagellate. 



O ~ 



Behind these are three segments of 

 the body without appendages. A 

 large carapax covers the anterior 

 portion of the body, and is pro- 

 longed into a spine in front. After- 

 ward the last three maxillipeds be- 

 come aborted, and then grow out 

 again in their permanent form. 

 The abdominal feet develop in suc- 

 cession from before backward, and 

 all are fully formed before the ap- 

 pendages of the three posterior tho- 

 racic segments appear. In the Alima type of devel- 

 opment, which has been followed through by Profes- 

 sor Brooks, it seems probable that the young leaves 

 the egg in nearly the Alima form, and in the youngest 

 stage known the six appendages, eight to thirteen, are 

 absent, although three of the corresponding segments 

 of the body are developed, while the abdominal seg- 

 ments and their appendages are well developed. None 

 of the thoracic members are biramous. From this, 

 which- corresponds to the Erichthus after the atrophy 

 of the appendages, a regular development produces 

 the adult form. 



There are two well-marked genera of Storaatopoda, 

 Squilla and Gonodactylus, the former being divided 

 into several sub-genera. Thirteen species of the 

 Squillidas are found in American waters, Squilla em- 

 pusa extending as far north as Newport, K.T., where 

 it burrows in the mud, forming large irregular holes. 

 The colors are very bright, green, red, yellow, and 

 black predominating. The large pincer in both genera 



. , , , , . . P .1 ' < -i T ^ FIG. 83. Advanced larva of Squilla em- 



is formed by the last joint or the leg folding upon the pu sa, enlarged. 



FIG. 82. Squilla empusa, mantis shrimp, reduced. 



