554 
Saw-flies, Gall-flies, Ichneumons, 
ants, bees, and wasps has long been a subject of popular interest and an 
object of much scientific observation and experimentation more or less 
rigorously conducted. Speculation, both popular and scientific, concerning 
the causal factors concerned has run a wide gamut, from the declaration 
of Bethe that ants are simply complex machines responding mechanically, 
with fixed strictly reflex reactions, to physico-chemical stimuli, to the anthro¬ 
pomorphic comparisons of the natura.-history popularizer, who reads into 
the behavior of the “wonderful little ant people” human emotions, human 
reason, intelligent discrimination, and volitional action. 
A difficulty met with at the very beginning of any discussion of the be¬ 
havior of social insects is the lack of precise definitions of three presumably 
classificatory terms distinguishing, on a basis of cause, three kinds of behavior 
or action, viz., reflexes, instincts, and intelligence. Another more funda¬ 
mental difficulty in the actual study and interpretation of animal behavior 
is the absolute lack in ourselves of any criterion or means of interpretation 
of action other than our experience of our own sensation and psychology. 
Nevertheless the matter can be, and is now being, undertaken in a rational 
and unbiased spirit, and is attaining important positive results based on 
observation and experiment conducted with rigorously scientific method 
and expressed with scientific caution. Although little more than an ap¬ 
preciable beginning has been made in this work, we can already dis¬ 
tinguish some of the springs or factors, both intrinsic and extrinsic, which 
determine the actions of these insects, and we can define scientifically some 
of the limitations as well as some of the possibilities of their purposeful 
behavior. 
Between the cleanly mechanical or reflex theory of Bethe, Uexkull, and 
others, and the reflexes plus instincts and animal-memory theory of Was- 
mann, Loeb, and Wheeler, or between this and the instincts plus intelligence 
theory of Lubbock and Forel, there is no sharp line, although between Bethe 
and Forel there is a wide gulf. What modern investigation has clearly and 
positively done is to cut away the anthropomorphism of the careless popu¬ 
larizer, and to compel a strong leaning toward a belief in the efficiency of 
reflex and instinct to explain most if not all of ant behavior. What would 
not have been heard with any patience at all a few years ago, that is, a purely 
mechanical, i.e., reflexive reaction to physico-chemical stimuli, explanation 
of many of the “wonderful” actions of ants, as their perception of paths, 
their recognition of nest-mates, and swift attack on strangers, their refrain 
from attack on other species living in symbiotic relations with them, etc., etc., 
is now heard with careful attention. Couple with this purely reflexive theory 
the theory of inherited specialized instincts developed by natural selection 
from widely diffused generalized instincts and most of us are inclined to 
