204 Wisconsin Academy of Sciences, Arts, and Letters. 
end which soon disappears in the abdomen and represents the total 
nerve supply of that part of the insect’s body. 
The supraoesophageal ganglion is broad, its central portion ex¬ 
tending anteriorly in a projection which may be an ocellar lobe 
(fig. 14, 0.1), though no ocelli are visible on the exterior of the 
head. Two lobes on the right and left of the median one send 
nerves to the mouthparts, and just lateral to these are the anten- 
nary lobes (fig. 14, a.n.). The largest lobes are the optic, (fig. 14, 
op.l.) reaching laterally almost to the eyes. The supraoesophageal 
ganglion ends posteriorly in two prominent projections which in 
sections seem largely cellular with little “ punktsubstanz ”, or 
medullary material, extending into them (fig. 14, p.l.). The func¬ 
tion of these is not clear. 
The supraoesophageal ganglion connects with the suboesophageal 
ganglion by the circumoesphageal commissures (fig. 15, c.o.c.) 
which pass from its anterior ventral surface around the oesophagus. 
The Respiratory System 
The tracheal system can be distinguished only in specimens 
which have been a short time in glycerine. So treated the air is re¬ 
tained in the tracheal tubes and they appear black against a trans¬ 
parent background. Even when thus prepared only parts of the 
system are evident; so that any reconstruction of the tracheae 
must be a composite from many specimens. 
The respiratory system of Troctes is of a simple type. In the 
abdomen are six pairs of stigmata or spiracles, one pair in each of 
the first six segments. From each a short trunk leads to a main 
lateral longitudinal one (fig. 16, l.t.) which extends the length of 
the abdomen and is continuous with one of the main trunks of the 
thorax and head. Each of the stigmatal trunks in the abdomen 
gives off typically a visceral branch (fig. 16, vs.b.) to the digestive 
and reproductive organs, a ventral branch (fig. 16, v.b.) to the 
ventral body wall, and a dorsal branch (fig. 16, d.b.) which sup¬ 
plies the dorsal region of the body with oxygen. In the posterior 
region of the abdomen the longitudinal trunks break up into nu¬ 
merous smaller branches which supply the last three segments. 
In the prothorax and in the head, the longitudinal trunks are con¬ 
nected to each other by transverse trunks (fig. 16, t.t. and h.t.), and 
in the head the tracheae are numerous and small, a large number 
of branches reaching into the mouthparts, antennae, and eyes. 
