THE SPINY LOBSTER OF SOUTHERN FLORIDA. 



2 93 



Adolescent females differ from the adults in the development of the fifth claw. 

 The dactyl of the young is more curved and more acute than the dactyl of the adult, 

 and the number and arrangement of the setae on the dactyl of the young also differ. 

 The cheloid part of the fifth claw is shorter in proportion to the dactyl in the young than 

 it is in the adults. 



Small individuals of both sexes are found in shallow water at all times and can be 

 caught by means of traps set there. Large numbers of them are often taken by the 

 fishermen for bait, and they are brought to market during stormy weather when fishing 

 is restricted to sheltered places. The adults are more commonly taken in deeper water, 

 but they are taken in large numbers in shallow water during migrations. 



MORPHOLOGICAL DIFFERENCES IN SEX. 



Adult spiny lobsters exhibit well-defined sexual dimorphism. The young of both 

 sexes can be distinguished readily, although the differences are not as well marked as 

 they are in the adults. The sexes can be distinguished by the fifth dactyl of the female, 

 the second pair of legs of the male, the pleo- 

 pods, the difference in the shape of the cara- 

 pace, and the development of the thoracic 

 sternum. 



FIFTH CLAW OF THE FEMALE. 



The fifth claw of the female (Fig. 267) 

 furnishes the most ready means of distin- 

 guishing the sexes. The most striking 

 difference between the dactyl of the male 

 and that of the female is the development 

 of a small chela on the fifth dactyl of the 

 latter. This chela is composed of spurlike 

 extensions of the propodus and dactyl, both parts being concave on their inner sur- 

 faces and provided with tufts of soft setae, those on the dactyl being longer. 



The fifth dactyl of the female is shorter in proportion to the length of the propodus 

 than the fifth dactyl of the male, and the number and arrangement of the setae differ 

 to a marked degree, since the dactyl of the female is almost naked. 



Spawn-bearing females have been observed using the fifth dactyls to manipulate 

 the eggs, and in one instance a female was observed to use the fifth dactyl to scrape off 

 the surface of the seminal vesicle just before the eggs were laid. 



SECOND PAIR OF LEGS OF THE MALE. 



The second pair of legs of the adult male (Fig. 268) is extraordinarily developed, 

 being so long that these legs are rarely used in walking and are usually extended forward. 

 The dactyl is long and curved and provided with a brush of long set3e which probably 

 aids in clinging to the shell of the female during copulation. (See Copulation, p. 305.) 



The second dactyl increases in length with age, becoming more curved, until, in 

 very old individuals, it is almost falcate. The setae also increase in length with age, 



Fig. 267. — Fith dactyl of spiny lobster, Panulirus argus. X 1.5 

 approximately, a, fifth dactyl of mature female: b. fifth 

 dactyl of immature female; c, fifth dactyl of mature mala. 



