478 P. W. CLAASSEN 
~but the spiracles of the eighth segment have migrated from the lateral 
margin to a position on the posterior margin of the dorsal surface, 
as shown in Plate XLI, 30. The ninth abdominal segment conse- 
quently is much smaller, being only about half as thick dorso-ventrally 
as the other segments. This better adapts the larva to live in its. burrow 
in a plant where an excess of moisture occurs. It is not at all uncommon 
to find a larva entirely submerged in the water with the exception of 
these large spiracles, which protrude above the surface of the water. 
These two spiracles are more than twice as large as the other abdominal 
spiracles. 
The arrangement of the tracheal system in the larva is shown in Plate 
XLI, 31. It consists of. two main longitudinal tubes, which originate 
from the spiracles of the eighth abdominal segment and extend as far 
forward as the first thoracic segment, where they are united by a transverse 
trunk. From this transverse trunk arise the tracheal tubes of the head. 
Paired spiracles are present on the meso- and metathorax and on the first 
eight abdominal segments. All of these spiracles are functional except 
those of the metathorax, which are much reduced and seem almost vestigial. 
Each of the spiracles, except those on the eighth abdominal segment, 
are connected with the main tracheal trunk of the body by small tubes, 
the tubes on the metathoracic segment being reduced to mere threads. 
Most of the tracheal branches of the body take their origin from the 
longitudinal trunk, near its Junctions with the spiracles. From the 
thoracic spiracles, only small, branching tubes originate. From. the first 
abdominal spiracle a large tracheal tube originates from the tube joining 
the spiracles to the longitudinal trunk, and smaller branches spring from 
the trunk. Segments 2, 3, 4, 5, and 6 of the abdomen each have a pair 
of large tubes arising from the main trunk just above the spiracles. These 
tubes branch out into two parts, as shown in Plate XLI, 31. Segment 
7 of the abdomen has a number of smaller branches, and segment 8 has 
a number of still smaller branches in front of the large spiracles. 
The pupa (Plate XLI, 23) 
Female, average length 32.85 mm., width 7.25 mm., male, length 28.5 mm., 
width 6.7 mm. Head, thorax, and appendages black. Abdomen dark brown.  Frontak 
prominence very weak. Wings extending back over two-thirds of the fourth abdominal 
segment. Prothorax about two-fifths of the length of the metathorax. Surface of 
the head and thorax rugose. Clypeo-labral suture very distinct. Labium distinct, the 
labial palpi nearly twice as long as labium. Maxillae extending to the posterior margin of 
