124 
Psyche 
[August-October 
METHODS OF ORIENTATION IN DRAGON-FLY LARVAE 
By C. E. Abbott 
Elgin, Illinois. 
Most terrestial insects orient themselves through vision, 
and most of them take advantage of the direction of light rays. 
Although other factors may influence the direction in which a 
given individual will travel, the visual, and possibly the olfactory, 
senses seem to be those chiefly utilized in maintaining a direct 
path. The only studies of a complete nature relating to this 
phenomenon in aquatic insects were made by Holmes (1905). 
In the following experiments, the larvae of Anax junius and 
some species of Aeschna were employed. Two larvae were taken 
from the water, and the left eye of one insect and the right eye of 
the other covered with asphaltum. As soon as the asphaltum 
hardened they were put back into the water for about an hour. 
They were then removed and placed on a sheet of white paper. 
Their courses were traced with a pencil as they crawled. Ten 
such tracings were taken at one time; the animal was then 
placed in the water and allowed to rest. Thirty tracings in all, 
were taken for each of the two insects. The animal always turned 
toward the side with the covered eye. Often, after a few trials, 
the paths were almost straight; showing that habit tended to 
overcome the turning. These experiments were conducted in 
diffuse daylight. 
Other experiments were tried with a beam from a 500 watt 
bulb. A larva with the left eye covered was placed at right angles 
to the beam and to the left of its source. In twenty-one trials it 
turned five times to the left, eight to the right, four times it fol- 
lowed a straight course, and finally turned four times to the right. 
On the following evening it turned seven times to the left, eighteen 
times to the right, once it took an irregular course, and once 
turned to the right. Two evenings later it first followed a straight 
course once, turned six times to the left, once followed a straight 
course, and finally turned seven times to the right. On the same 
evening, this insect was tried facing the light. Once it followed a 
