126 
Psyche 
[December 
on the posterior lateral surface of the anterior lobe, e.g. 
that portion derived from the larval metathoracic ganglion. 
These cells, like those supplying the mesothoracic legs, give 
off large axons which in turn give off side branches to the 
neuropile before passing to the leg commissure. The sensory 
fibers (1) which pass from the metathoracic legs to the 
ganglia end in the neuropile of the posterior lobe ; one group 
• ends in the anterior ventral portion and the other in the 
dorsal median area, but neither extends into the anterior 
lobe. 
The motor fibers (g) which innervate the thoracic muscles 
(and thus supply the impulses for flight) originate in cells 
located in the posterior ventral lateral portion of the ante- 
rior lobe. These fibers pass dorsad in the neuropile and give 
off side branches to the surrounding areas, especially the 
dorsal motor area, and pass among the ganglion cells to the 
surface in a dorsal lateral position (W M C) from which 
point they pass directly among the thoracic muscles. 
The axons of the motor cells of the posterior lobe (i, i', i") 
all pass through the commissure (m) to the abdominal 
region. Each gives off fibers to the surrounding neuropile as 
it passes through it. 
There are many small association fibers which pass from 
one section of the neuropile to another, but they have not 
been shown in the figures or discussed. This description is 
primarily concerned with the major tracts. 
