PROC. ENTOMOL. SOC. WASH. 96(3). 1994. pp. 527-532 INTERSPECIFIC MORPHOMETRIC AFFINITIES IN AMBRYSUS (HEMIPTERA: NAUCORIDAE) Robert W. Sites and Michael R. Willig (RWS) Wilbur R. Enns Entomology Museum, Department of Entomology, University of Missouri, Columbia, Missouri 6521 1; (MRW) Ecology Program, Department of Bio-logical Sciences and The Museum, Texas Tech University, Lubbock, Texas 79409-3131. Abstract. — MorphomeUic variation in 15 characters was assessed among adults of 22 species of Ainbrysus. Generally, 1 individuals of each sex were measured for each species, although fewer than 10 specimens were available for some species. Because a multivariate analysis of variance revealed that interspecific differences were dependent on sex, sub-sequent analyses were conducted on males and females separately. All characters were individually significant in distinguishing among species based on univariate statistics. Moreover, each of the 22 species formed a species-specific cluster in multidimensional space (Discriminant Function Analysis) and was distinct from the others based on pairwise f-tests. With Principal Components Analysis, the first principal component was repre-sented by positive loadings associated with aspects of length. Thus, most of the morpho-metric distinction among Ambrysiis species is represented by factors associated with size. Five additional components were important (each component >0.5% of variation) and provided additional interspecific resolution based on shape. In general, we identified a group of 13 core species with similar shape, surrounded by 9 peripheral species. Clear distinction of the four currently-recognized subgenera did not occur, and the inclusion of additional species would likely blur these already tenuous distinctions. Moreover, con-tinued recognition of current subgeneric groupings may represent an anachronism. None-theless, a number ofADibrysiis species occupying currently-recognized infrageneric groups (Acyttarus. Picrops, signoreti group) do exhibit extreme morphologies, which may cor-respond to unusual habitats. Based on inconsistencies in morphometric affinities of other currently recognized taxa within the genus (subgenera Syncollus and Anibrysus). the small number of characters defining the subgenera, and wide ecological variation within the nominate subgenus, we recommend a phylogenetic analysis of the genus. A cladistic analysis of discrete characters is required to conclusively evaluate phylogenies and arrive at a natural infrageneric classification of Ambrysus. Key Words: Naucoridae, Ambrysiis. morphometries, phenetics The Naucoridae, or creeping water bugs, catalog of the world naucorid fauna, and are predacious insects common in both four additional species have been described temperate and tropical aquatic systems. The (Polhemus and Polhemus 1981, 1983). genus Ambrysiis is one of the most species-Moreover, many undescribed species from rich in the family (Usinger 1946), although Latin America and one from the western it is restricted to the New World. La Rivers United States are represented in collections (1971, 1974, 1976) listed 69 species in his (J. T. Polhemus, pers. comm.). Ecologically,
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