INTRODUCTION AND METHODS. 11 



way. Many new facts are revealed as to flight, speed of working, constancy, 

 seasonal adjustment in relation to changing maxima of flowering, and so 

 forth. 



The analysis of behavior rests upon three factors — instinct, habit, and 

 individual adjustment. Instinct is here regarded as fixed habit, and can 

 be largely evaluated by investigating the comparative behavior of related 

 species and genera. It is probable that habit is constantly passing over 

 into instinct, as seems well illustrated by the perennial adjustment made 

 by groups of species and individuals in the particular floral environment 

 to which their round of activities is restricted. As both observation 

 and experiment have shown, visits to flowers are largely determined by 

 habit, and it is impossible to secure conclusive evidence as to the senses 

 and mental powers of insects without eliminating this actor. The best, 

 though hardly the simplest, way of doing this is to base all studies of 

 attraction, for example, upon the use of individuals that have just hatched 

 and hence have had no opportunity to form habits. This demands the 

 location and control of nests and the marking of individuals as they emerge. 

 It can be done in a less exact manner by transferring nests or hives to a 

 different climax, as from the plains at the foot of Pike's Peak to the montane 

 or alpine zone, but even here marking or cages must be employed for 

 accurate results, except where a species peculiar to the plains is used. 

 Pollination cages afford the best means of complete control, but those so 

 far employed have separated nest and flower group, with the result that 

 the caged bees finally became panic-stricken. Cages several meters long 

 and high enough to accommodate an observer when seated, into which nests 

 are introduced before the young emerge, furnish an almost ideal installation 

 for the study of initial responses to color, form, and odor and the gradual 

 fixation of habits. These can then be removed with their occupants to a 

 totally different group of species, or the flowers to which they are accus- 

 tomed can be mutilated to call forth new responses and the consequent 

 adjustment of habits to new conditions. Here, as in all experimental 

 ecology, the basic problem is to secure laboratory control under field 

 conditions, and the pollination cage appears much the best solution. 

 However, there will always remain certain experiments that can be carried 

 on best or solely in the laboratory, where maximum control, uniformity, 

 and accuracy can be secured. The requisite technique has been so 

 carefully developed by Frisch (1914, 1919) and Knoll (1921, 1922) that 

 their methods will serve as the point of departure for all such work in 

 this field (cf. also Porsch, 1922:485). 



The most conclusive evidence as to the role of color in attraction has 

 been furnished by insects with the antennae coated or amputated, even 

 Plateau admitting its cogency. The relatively small number of experi- 

 ments made with anthophilous insects indicate the desirability of extending 

 such work, and the questions raised by Mclndoo's researches render this 

 imperative. Owing to the injury usually caused by the amputation or 

 excision of the antennae or other organs, the chief task is to discover a 

 substance that will coat them with litt'.e or no injury and that can not be 

 readily removed. All substances that contain alcohol, turpentine, essential 

 oils, etc., must be avoided and the preference given to mixtures of paraffin 



