746 | CHARLES PauL ALEXANDER 
dolabina), or are ventral only (Rhamphidaria, Ularia, Epiphragmaria, 
and most Pedicuni). In number they range from four (on abdominal | 
segments 4 to 7) in most Pediciini, to five or six (on abdominal segments 2 
to 7) in Ularia, Epiphragmaria, and other forms. 
Organs of respiration 
The spiracular disk.— The posterior end of the body is usually truncated, 
bearing the two spiracles and surrounded by a number of fleshy lobes. 
These lobes vary much in their shape and armature, and range in number 
from two in the Pedicaria and the Antocharia to six or eight in the Tipulinae. 
The inner faces of the lobes are often lined with brown or black horny 
plates, which serve as points of attachment for the longitudinal muscles. 
Their arrangement and Ceerounon: are of great service in_ specific 
classification. 
The Limnobaria usually have the lobes surrounding the spiracular 
disk indistinct; the Antocharia have two long ventral lobes; the Rham- 
phidaria five lobes; the Ellipteraria and the Dicranoptycharia four lobes. 
In the Eriopterini, the Elephantomyaria and some Eriopteraria have 
four lobes; the majority of species of the latter division have five. In 
these last-named species the disk is almost squarely truncated, and the 
five lobes are subequal and stellate in appearance. 
The Hexatomini usually have four lobes, with the ventral pair longer 
than the lateral pair. Ina few cases only (Ularia, Dicranophragma, 
Poecilostola), a reduced mid-dorsal lobe is present. In the more specialized 
forms the lateral lobes also tend to reduce, simultaneously with the 
elongation of the ventral lobes. In this tribe the disk is fringed with long 
hairs, which are sometimes excessively elongate, especially on the ventral 
lobes where they appear as long fringes of delicate hairs that spread out 
on the surface film of the water as broad fans. Such fringes are found 
in a large number of Hexatomini and also in the Adelphomyaria (sup- 
position). Near the tips of the ventral lobes, but inside this fringe of 
hairs, are often inserted one or more stiff sensory bristles. 
In the Pediciini, the Pedicaria have two lobes and the Pee ceck he: 
(supposition) have four. In the former division the lobes are ventral 
in position and are almost naked. 
The Cylindrotominae have six rather indistinct lobes in Cylindrotoma, 
and four in the other genera. 
