STOMATOPODA LARVAL HISTORY 



143 



with the thoracic appendages developed as biramous organs as far 

 as the fifth pair, and with a single abdominal pair of limbs. 



The abdominal series of limbs is next completed ; the second 

 thoracic limb assumes its 

 adult raptorial structure, 

 but the succeeding three 

 limbs become greatly re- 

 duced and -may entirely 

 degenerate, leaving the 

 posterior six thoracic 

 segments without limbs. 



Usually the anterior 

 three pairs are only reduced, and then redevelop side by side 

 with the small posterior limbs as they appear. This larva is 

 then termed the "Erich thus" (Fig. 100); but when they com- 



FIG. 99. Erichthoidina larva of a Stomatopod, with 

 five pairs of maxillipedes, and the first pair of 

 abdominal appendages, x 10. (From Balfour, 

 after Glaus.) 



FIG. 100. Older Erich thus larva, with six pairs of abdominal appendages, x 15. 

 (From Balfour, after Claus. ) 



pletely disappear the larva is called a " Pseudozoaea," owing to 

 its resemblance to the Zoaea stage of the Decapoda, which is 

 also characterised by the suppressed development of the thoracic 

 segments. 



The so-called " Alinia " larva of Squilla is also a Pseudozoaea, 

 but it is apparently arrived at directly without the previous 

 formation and degeneration of the anterior thoracic limbs, the 

 larva hatching out from the egg in the Pseudozoaeal stage. 



Fam. Squillidae. Of the six known genera none extend 

 into the cold subarctic seas ; the majority are characteristic of 

 the warm or tropical seas (Gonodactylus), some of the species 

 having very wide ranges, e.g. G. cliiragra, which is completely 

 circumtropical, and appears to have entered the Mediterranean at 

 some period, though it is very rare there. 



