A PHYLOGENETIC INVESTIGATION OF HYDROVATUS, 
METHLINI AND OTHER PLESIOTYPIC HYDROPORINES 
(COLEOPTERA: DYTISCIDAE)* 
By G. William Wolfe 
Department of Entomology and Economic Zoology, 
Cook College, New Jersey Agricultural Experiment Station, 
Rutgers University, New Brunswick, N .J. 08903 
Introduction 
Phylogenetic relationships of the Dytiscidae are receiving in- 
creased attention (e.g. Burmeister 1976, 1980; Brancucci and Ruh- 
nau 1985, Dettner 1985). This paper is the fifth in a series on 
primitive hydroporine genera (Wolfe and Matta 1981; Wolfe 1985; 
Roughley and Wolfe, in press; and Wolfe and Roughley, in press). 
The first purpose of this paper is to investigate new discoveries 
concerning the remarkable abdominal structure of methlines and 
members of Hydrovatus Motschulsky. The peculiar modifications 
of terminal abdominal terga of members of Hydrovatus and Meth- 
lini provide good evidence for monophyly of these tax&<The second 
purpose is to revise a previous hypothesis (Wolfe 1985) of relation- 
ships among plesiotypic hydroporines in light of: 1) the new evi- 
dence regarding hydrovatine and methline monophyly, 2) more 
information on Laccornellus Roughley and Wolfe, 3) different 
interpretations of some character systems, and 4) computer gener- 
ated phytogenies. 
Materials and Methods 
Analyzed species are listed in Table 1. Authors of species and 
genera are listed the first time a name is used in text only if the name 
is not listed in Table 1. Table 2 lists characters used in this analysis 
but see Wolfe (1985) for complete details and illustrations for char- 
acters 1-18. 
Dissecting, illustrating, and scanning electron microscope (SEM) 
techniques are presented in Wolfe (1985). In order to understand the 
* Manuscript received by the editor April 20, 1987. 
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