148 Journal New York Entomological Society. t^'°'- >^>^ii- 



from setigerous punctures. The terminal setse of the labial palpae 

 are dialatcd, PI. Ill, figs. 3 and 5. The arrangement of setigerous 

 punctures on the labrum is shown in PI. Ill, fig. 2; on the head in 

 PI. Ill, figs. 3 and 4. 



Thorax. — First thoracic segment heavily chitinized and without 

 gills. Second and third segments thinly chitinized and witli a single 

 group of from two to five unbranched gills above each leg. The dis- 

 tribution of set?e on the dorsum is shown in fig. i, PI. IV. On the 

 ventral side there are numerous small setse, which are especially 

 abundant on the legs. 



Abdomen. — The first eight abdominal segments have filamentous, 

 unbranched gills distributed in two rows, supra- and infra-stigmatal 

 in position. The supra-stigmatal gills occur in groups of from two to 

 four near the cephalic border of the segment. Variation in the num- 

 ber of these gills occurs in different individuals, and even on the two 

 sides of the same segment of the same individual. A single supra- 

 stigmatal gill may be present near the caudal margin of any abdom- 

 inal segment. This gill, when present on one side, may be absent 

 from the other side of the same segment. The infra-stigmatal gills 

 are arranged in a single, nearly straight row, along each side of the 

 first nine abdominal segments. From three to five of these gills occur 

 on each segment, arising from lateral folds of the body wall. On one 

 specimen in my possession a single dorsal gill is present near the 

 caudal border of the ninth abdominal segment, midway between the 

 mid-dorsal line and the lateral margin. The tenth abdominal segment 

 is without gills and is roundly bilobed at its caudal extremity. On 

 abdominal segments three to six, inclusive, there are oval prolegs, 

 each ending in a terminal ring of about thirty-two hooks. Long and 

 short hooks alternate on these circles. On the last abdominal seg- 

 ment the prolegs are more oval in outline than on the preceding 

 segments and the hooks, about fifteen in number, are arranged in a 

 single line with their bases pointing cephalad, instead of forming a 

 circle as on the other segments. 



Young Larvae. — The young larv.-c have noticeably fewer gills than 

 old larvae. The smallest specimen in my possession (length 3 mm.) 

 has as many as four infrastigmatal gills on only one side of one seg- 

 ment. Other clusters of infrastigmatals are composed of three or 

 two gills. The superstigmatals also average fewer than on the mature 



