NO. LT NAIADS OF DRAGONFLY GENUS PLATHEMIS—LEVINE 17 
of the costal margin and a very minute branch posteriorly to connect 
with the radius. 
The radius (R) is of greater extent than the subcosta. It is deeply 
forked in the region of the nodus (nd) just posterior to the subcostal 
fork. The main portion of the radial trachea proceeds unbranched to 
the apex of the wing where it sends a minute branch forward. The 
radial sector (Rs), or posterior branch of the radius, lies across the 
base of the terminal fork of the median trachea and extends out to 
occupy the field between M, and Msg. 
The media (M) is 4-branched. At approximately one-third of the 
distance from base to apex it bends slightly posteriorly and gives off 
a narrow trachea, M4, which proceeds almost to the wing margin. 
Farther along its extent it gives off a second posterior branch, Ms, 
which lies just above and parallel to M, and extends almost to the 
wing margin. At a point just posterior to the radial fork the median 
trachea again forks, this time sending one branch, M,, nearly to the 
wing margin to occupy the field just above the radial sector and a 
second branch, M,, to the wing apex posterior and parallel to the 
radius. 
The cubitus (Cu) bends abruptly posteriorly just below the first 
forking of the median trachea and forks once into Cu, and Cup, the 
first of which almost reaches the hind margin of the wing. 
The anal trunk (A) is crowded forward against the base of the 
cubital trachea. It loops forward under the cubitus and then returns 
to its original level via the anal crossing. The anal trachea then 
descends slightly and forks twice. 
In the hind wing (ws) the tracheation is almost identical with that 
of the fore wing and differs only in the extent of certain tracheae. 
The hind-wing pad is expanded posteriorly and subsequently the 
cubital and anal tracheae are of greater extent than in the fore wing, 
which has not undergone such an expansion. 
LEGS 
The legs of Plathemis lydia (figs. 18, 19) are long and slender. The 
forelegs are subequal in length to the mesothoracic legs, which in turn 
are considerably smaller than the metathoracic legs. The differences in 
sizes of the legs is accounted for primarily by differences in length 
of the femur, tibia, and tarsus since the coxa and trochanter are 
almost identical in size in all three pairs of legs. 
The coxa (cx) or basal leg segment is of moderate size and more 
or less conical in shape. It articulates with the pleural coxal process 
