1925] 
Vision and Chemical Sense in Anax Larvce 
315 
THE RELATIVE IMPORTANCE OF VISION AND THE 
CHEMICAL SENSE IN ANAX LARVAE. 
Cyril E. Abbott. 
University of Wisconsin, Madison, Wis. 
General observations and experimental work on the larvae of 
Anax junius for over a year, seemed to indicate that the responses 
of these insects are chiefly dependent on the sense of sight. Thus 
taking of food, in particular, seems to be the result of reactions 
to form and movement. General observation also indicated that 
the chemical sense was correspondingly weak. Although the 
question of image-formation in insects has been treated by Cole 
(1907), Demoll (1910), Forel (1908), and Seitz (1912); and the 
chemical sense by numerous authorities, including Forel (1908), 
Kafka (1918), and Lubbock (1888); apparently no work has 
been done with dragon-fly larvae. Accordingly, two experiments 
were made; one to test the reactions of the larvae to form, the 
other to determine whether or not they would react to the 
chemical emanations from distant objects. Each experiment is 
a check on the other, and both are related to prehension. 
Reaction to Form. 
Individual. 
1. Food: 
Triangle: 
2. Food: 
Triangle: 
3. Food: 
Triangle: 
4. Food: 
Triangle: 
5. Food: 
Triangle: 
6. Food: 
Triangle: 
7. Food: 
Triangle: 
8. Food: 
Triangle: 
9. Food: 
Triangle: 
10. Food: 
Triangle: 
Positive responses 
15 
4 
9 
1 
11 
0 
10 
4 
9 
1 
8 
o 
13 
0 
10 
1 
9 
o 
11 
o 
Negative responses 
o 
7 
7 
12 
2 
9 
o 
15 
5 
11 
5 
13 
2 
16 
o 
15 
7 
12 
4 
8 
