54 ENTOMOLOGICAL NEWS [Feb., 'll 



The three caudal gills together are much wider than the abdomen 

 at its widest part. Each one is petiolate at base and much enlarged in 

 all diameters beyond the petiole. Median gill approximately equal in 

 length to that of segments 8+9+10, much enlarged dorso-ventrally and 

 less so laterally immediately after the petiole, thence increasing in 

 height gradually and slightly to the apex which is triangulate in profile 

 view, the ventral angle most obtuse, the median angle most acute, the 

 dorsal angle projecting not as far caudad as the other two. At a little 

 less than half length from the base there is an angular protuberance on 

 each side at about one-fourth height of the gill from the dorsal crest, 

 so that there are in all five angular projections on this gill. Most of 

 the chitin of this gill is brown and opaque, or at most only translucent, 

 and is covered with scales, but on each of the two lateral faces there is 

 an area of colorless transparent chitin occupying the ventral two-fifths 

 of the height and about four-fifths of the length from the base caudad 

 (PI. II, fig. 14) lacking scales. 



Each lateral caudal gill is somewhat longer than the median gill, 

 roughly triangular in cross-section, one surface being convex, the other 

 two approximately plane. These latter two are ventral and internal 

 (mesial) respectively, the convex surface is lateral (external) and 

 dorsal and greater in extent than either of the other two. There are 

 four angular protuberances : one at half-length, or a little less than 

 half-length, of the gill on the middle of the convex dorso-external sur- 

 face; one at three-fourths of the length of the gill on the convex sur- 

 face close to the margin of the mesial surface; one at seven-eighths of 

 the length of the gill on the middle of the convex surface ; and one, the 

 most obtuse, forming the apex of the gill. The convex dorso-external 

 surface of the gill is of brown chitin and scale-covered, the ventral and 

 mesial surfaces chiefly of colorless, transparent chitin and lacking scales, 

 except along the margins where each meets the dorso-external sur- 

 face respectively. (PI. II, figs. 3, 4, 9, 14, 15). 



Between the bases of the three caudal gills are the rudiments of 

 the superior appendages or 'cercoids' of the imago (PI. II, figs. 7, 8, 

 sa) and the supra-anal (spl) and sub-anal (sbl) laminae. The rudi- 

 ments of the 'cercoids' are simple, cylindrical or conical, with rounded 

 apices, and vary in length, in the four larvae, from about one-third to 

 more than one-half of the length of abdominal segment 10. The sub- 

 anal plates reach to about mid-length of the 'cercoids' ; each one is de- 

 pressed, its apex squarely truncate but produced apparently into a short 

 spine at its mesial angle when viewed dorsally or ventrally; this ap- 

 parent spine is the end view of a vertical lamina. 



The main abdominal traclieal trunks and their branches are shown 

 in PI. Ill, figs. 22, 20; PI. II, figs. 9, 17, 19. The ventral gills of ab- 

 dominal segments 2-7 receive each two tracheae from two separate 



