LARVAE OF SERGESTES 



49 



Mastigopus I (Figs. 39 a, b, 40). Length 2-6 mm. Rostrum o-6 mm. 



Rostrum reaching beyond segment i of antennule. Supraorbital spines minute; 

 hepatic, marginal and posterior dorsal spines absent. 



Abdominal somites 1-3 without dorsal spines ; somites 4 and 5 with large dorsal spines. 

 All somites with rather large pleural points. No median ventral spines. Telson narrow, 

 greatest width nearly one-third length, with small apical fork. 



Fig. 39. S. pectinattis. a, Mastigopus i ; b, telson. 



Eye very large, asymmetrical, with very short stalk, and turned backwards in charac- 

 teristic manner. Antennal scale very long and slender (11 : i); fiagellum much longer 

 than body, without conspicuous setae, the end 

 segments slightly swollen. Legs without trace of 

 exopods. Legs 4 and 5 remaining as rather large 

 vestiges. Maxillipede 3 with spine at outer distal 

 end of carpus. Pleopods without endopods. Exopod 

 of uropod six times as long as wide ; setose part twice 

 as long as bare part. 



Colour. Body colourless except for a vermilion 

 patch in thorax. Antennal flagellum red at end and 

 also, in later stages, with bands of red. In later stages 

 the red in thorax extends to mouth region and base 

 of eye, and red patches appear in somites 2-4 of 

 abdomen. 



In early stages the body is bent in a characteristic 

 way as shown in Fig. 39. 



The length of the antennal flagellum rapidly in- 

 creases with age, as follows. 



Mastigopus I. Usually a little longer than body, 

 but sometimes (Fig. 40) much longer, without kink, 

 and with red at end, where it is slightly swollen. 



Mastigopus 2 (moulted from i). More than three 

 times length of body, with several red portions at intervals, and with kink before first 

 third. Dilated at end. 



Fig. 40. S. pecdnatus. Mastigopus i . 



