182 
Psyche 
[September 
.SOME EXPERIMENTS ON THE NERVOUS PHYSIOLOGY 
OF DRAGON-FLY LARVAE. 
By C. E. Abbott, 
Elgin, Illinois. 
A number of students of insect physiology have attacked 
the problem of nervous control. In 1911 Hilton, while making 
purely morphological studies of certain insects, discovered that 
the supraoesophageal ganglion consisted largely of sensory 
elements, whereas the suboesophageal ganglion was rich in motor 
nerves. But as far as I am aware, the only work of a functional 
nature that has been done in connection with dragon-fly larvae is 
that of Baldus (1924). 
During the past summer it was my good fortune to be 
located in Madison, Wisconsin, where it was possible to obtain 
and observe many larval specimens of Anax junius and Aeschna 
umbrosa. I took this opportunity to study the nervous physiolo- 
gy of these insects. 
Before considering the experiments, it is necessary to say 
something about the gross anatomy of the nervous system. 
Besides the brain and the suboesophageal ganglion, this consists 
of three thoracic and seven abdominal ganglia. The prothoracic 
ganglion lies midway between the bases of the first pair of legs. 
The other thoracic ganglia are very close to each other; both 
are near the middle pair of legs. The first abdominal ganglion 
lies in the second segment of the abdomen, and the remaining 
ganglia lie in the segments following, so that the seventh or 
terminal ganglion lies in the eighth abdominal division. Each 
ganglion is connected to the adjoining parts of the body by a pair 
of lateral nerve fibers. The thoracic ganglia are all large, as also 
is the terminal abdominal ganglion, but the remaining nerve 
masses are small. With the exception of the brain, the entire 
nervous system lies so near the ventral surface of the animal 
that it is visible through the chitin. The suboesophageal cannot 
