rate (ranging from sixty frames/sec to one frame/min) appropriate for the 
relative speed of the organisms. When the BUGWATCHER INPUT operator is 
executed, the computer accepts digitized image information from the 
Bugwatcher at the selected frame rate. Each threshold point is represented in 
Cartesian coordinates with 8-bit resolution for each of two orthogonal 
components. A video frame is represented within the resultant data structure as 
a data vector with a variable number of such points as its data elements. An 
entire record (or “video file”) consists of a temporally ordered sequence of 
such vectors. 
The Bugsystem was originally developed for the investigation of the 
behavior of motile microorganisms (2). In this application, the organisms are 
viewed under dark-field illumination swimming within a well slide upon the 
stage of a compound microscope. However, automatic digitization of data is 
possible for any study of moving objects for which “clean” video records are 
available. One of us (Wilson) is currently using the second generation system to 
study the effects of plane polarized light upon the behavior of aquatic 
arthropods. The animals move freely within a cylindrical aquarium (diameter » 
20 cm) under bright-fleld illumination and are viewed using a macro lens 
attached to the television camera. Use of video tape as a storage medium allows 
experiments to be conducted in a laboratory remote from the site at which the 
data are analyzed. 
Occasionally video recordings are not “clean” enough to allow fully 
automated digitization (e.g., data collected in the field) or the digitized images 
are too crude to provide information about details of an organism’s anatomical 
structure (e.g., the orientation of its eyes). A technique has been developed to 
expedite manual analysis of such data. Using the PICK operators, the video 
tape is examined frame-by-frame. The user selects points upon the screen of a 
video monitor using a video cursor controlled by a JOYSTICK. A synthetic 
video signal representing a tiny bright dot is sent to the Bugwatcher which, in 
turn, sends digitized video information to the computer. Because averaging 
algorithms are employed, this method affords higher spatial resolution than 
does fully automated input: each coordinate in the resultant data structure 
may have 8-9 significant bits in comparison to the 7-8 bits of the normally 
digitized input data. 
Input of video data to the computer effects a mapping of the image as seen 
upon a television screen onto a two dimensional representational space. 
Distances within this space (“Bugspace”) are measured in arbitrary internal 
units (or “Bugwatcher units”) and, therefore, must be scaled. Using the LIVE 
INPUT operator, the Bugwatcher processed image of a ruler (or any object of 
known length)-recorded under the same conditions used in gathering 
behavioral data-is displayed on the screen of a CRT terminal and two points 
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