dependent upon the collection of temporal sequences of spatial information. 
Cinematography is the classical method used to gather such information. 
Behavioral variables such as the position of an organism, its orientation, and 
angles of flection of its appendages are extracted from the motion pictures by 
means of frame-by-frame analysis. An important advantage of this technique is 
its flexibility; it may, in principle, be employed in the investigation of any 
overt behavior which can be photographed. However, two factors preclude the 
widespread use of this method: (1) manual quantitization via frame-by-frame 
analysis is a lengthy and tedious process; and (2) once the data is obtained, a 
substantial amount of subsequent data processing may be required in its 
analysis. 
The Bugsystem (2, 4, 5) was designed to enable the acquisition and 
processing of video data by a minicomputer. Behavioral data are initially 
recorded using standard closed-circuit television equipment. These data are 
analyzed by replaying a video tape into a specially designed video-to-digital 
processor (christened the “Bugwatcher”). This device acts as an edge detector, 
greatly reducing the information flow to the computer and thereby allowing 
the real-time collection of spatial coordinates delineating the outlines of 
moving organisms. Frame-by-frame analysis of digitized video data is achieved 
through the use of specially designed programs tailored to the task of 
quantizing behavioral variables of interest to the researcher. 
The original version of the Bugsystem was developed by Greaves and 
implemented on an IBM 1800 computer at the University of California, Santa 
Barbara. This prototype system, previously described by Greaves (5), has been 
utilized by Hand and Schmidt (6) and by Wilson (8) to investigate the 
photokineses and phototaxes of marine dinoflagellates. However, several 
features of this system severely limited the domain of its application. 
Supported by a research grant from the Environmental Protection Agency, we 
have developed a second generation Bugsystem. Our explicit goal in the design 
of this system was to provide a flexible tool for the quantitative investigation 
of behavior, a system capable of realizing much of the potential of 
frame-by-frame analytic techniques. 
The purpose of this paper is to describe this second generation Bugsystem, 
emphasizing the way in which certain hardware and software refinements have 
expanded the scope of questions which may be conveniently answered by 
means of “bugwatching.” We discuss the way in which the user interacts with 
the system via a specially formulated “Behavioral Research Language” and the 
way in which this language has been implemented upon physical machines. We 
also describe the input of data to the system, the processing and display of 
behavioral data, and a variety of experimental strategies accommodated by the 
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