8 B R E V I O E A n/mT oseum of Comparative Zoology lAM ^ 1995 us ISSN 0006-9698 Cambridge, Mass. 10 January 1995 , Number 502 Hai"< v/ UNIVER: >i 1 I A COMPUTER APPROACH TO THE COMPARISON AND IDENTIFICATION OF SPECIES IN DIFFICULT TAXONOMIC GROUPS* Ernest E. Williams,'^ Hugh Rand,^ A. Stanley Rand,^ AND Robert J. CHara"* Abstract. A computer program for the identification of unknown taxa in "difficult groups" based on matching rather than sequential exclusion is proposed as a substitute for both the conventional dichotomous key and for the random entry matrix that has been suggested as a replacement for the dichotomous key. The matching program is modeled after the steps that a practicing taxonomist would employ in the identification of an unknown specimen: 1. Data for the unknown are compiled. 2. Data for the unknown are compared with those of relevant known taxa. 3. On the basis of the comparison, certain of the named taxa are considered possible matches with the unknown. 4. Final choice of the named taxon best matching the unknown is made and confirmed from additional data. If there is no match, the possibility of an undescribed species must be confronted. * Apple, HyperCard, and Macintosh are registered trademarks of Apple Computer, Inc. Turbo BASIC is a registered trademark of Borland International, Inc. IBM is a registered trademark of International Business Machines Corporation. MS-DOS is a registered trademark of Microsoft Corporation. ' Museum of Comparative Zoology, Harvard University, Cambridge, Massachu-setts 02138. -Department of Applied Mathematics, University of Washington, Seattle, Wash-ington 98195. ' Smithsonian Tropical Research Institute, P.O. Box 2072, Balboa, Republic of Panama. ^ Center for Critical Inquiry in the Liberal Arts, University of North Carolina at Greensboro, Greensboro, North Carolina 21412-5001. ' To whom reprint requests should be addressed.