Cicada orni Linnaeus is among the most common and widespread cicadas in Portugal, and, unless a critical study of the male genitalia is made, it is easily confused with the much less widely distributed C. Barbara lusitanica Boulard. These species are morphologically very similar and sometimes difficult to separate using existing keys. This study attempts to test the discriminating capabilities of numerical techniques commonly used for classificatory purposes, as well as to discover the most effective characters to distinguish between the two species. For these purposes, cluster analysis and principal component analysis were applied to a sample of 64 male specimens characterized by 40 characters (33 derived from the external morphology and 7 from genitalia). In WPGMA cluster analysis, product-moment correlations gave a better separation between these species than did taxonomic distance coefficients; moreover, the analysis derived from the genital characters alone gave better separation than the analyses based on the33 external characters. Principal component analysis yielded a clear, interspecific separation along the first axis. The best characters to discriminate between males of the two species were the lengths of the pygofer (and its dorsal spine), the tenth abdominal segment, and the appendages of the latter (which are smaller in barbara lusitanica), as well as the width of the shaft of the aedeagus (thinner in orni). Finally, the uniformity of the general clustering pattern resulting from the two multivariate techniques suggests the presence of two distinct species, as also clearly indicated by behavioral data.
Quartau, J. A.
"A numerical taxonomic analysis of interspecific morphological differences in two closely related species of Cicada (Homoptera, Cicadidae) in Portugal,"
Great Basin Naturalist Memoirs: Vol. 12
, Article 12.
Available at: http://scholarsarchive.byu.edu/gbnm/vol12/iss1/12