28 



PROCEEDINGS OF THE NATIONAL MUSEUM 



antenna has essentially the same form as the adult female but has no 

 ventral bristles on the 4th joint. The number of ventral bristles on 

 the 4th joint increases with each instar: 1 in instar IV, 2 in instar V, 

 and 3 m the adult. The outer bristle is formed first and each succeed- 

 ing bristle is added on the inside. 



In the adult male the 6th joint is elongate; the 5th joint consists of 

 a small triangle wedged ventraUy between the 4th and 6th joints, and 

 the sensory bristle has at its base a small cuplike process bearing 

 numerous thin filaments. 



Second antenna: In the embryo the exopodite of the 2nd antenna 

 is divided into 11 joints: each joint from 4 to 10 bears a long hirsute 

 bristle; joint 11 bears 1 long hirsute bristle and 1 short bristle. Mar- 

 ginal hairs on the bristles of the exopodite are relatively longer on the 

 embryo than on older stages. Except for small variations in distribu- 

 ition of marginal spines on bristles, the exopodite of the 2nd antenna 

 is essentially the same from instar III to the adult. The endopodite 



Figure 14. — Sarsiella zostericola Cushman, stage IV cf from California: a, 1st antenna, 

 3rd to end joints, bristles shown only on 3rd and 4th joints; b, 2nd antenna, endopodite, 

 1st and 2nd joints of exopodite; c, 7th limb. (Scale in microns.) 



of the embryo consists of a node without bristles. The endopodite on 

 the female is 1-jointed and has 1 terminal bristle on all stages from 

 instar III through the adidt, but the number of dorsal bristles varies : 



1 on instar III, 1-2 on instar IV, 2 on instar V and the adult. 



In instar III of the male the endopodite is 2-jomted with 1 dorsal 

 bristle on the 1st joint and a small terminal bristle on the 2nd; in 

 instar TV the 1st joint has 1-2 dorsal bristles, and the 2nd joint has 



2 subequal bristles near the middle and 1 short stubby bristle termi- 

 nally; instar V is 3-jointed: the 1st joint has 2 bristles near the base; 



