54 ENTOMOLOGICAL NEWS [Feb., ’11 
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 
(Pl. 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 (sf/) and sub-anal (sb/) 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 tracheal trunks and their branches are shown 
in Pl. III, figs. 22, 20; Pl. II, figs. 9, 17, 19. The ventral gills of ab- 
dominal segments 2-7 receive each two tracheae from two separate 
