Morphological and chemotaxonomic identification of Blattella cockroaches (Blattaria : Blattellidae) from Taiwan and selected Pacific Basin locations

Abstract

A total of 58 museum specimens of Blattella cockroaches from Taiwan was identified on the basis of traditional morphological traits. Cuticular hydrocarbon analysis was performed for each specimen by means of gas chromatography, and this was compared with morphology-based identifications. Additionally, 38 specimens captured at field sites were subjected to hydrocarbon analysis. Four of the five species known to occur in Taiwan were encountered. B. bisignata was the predominant species (n = 67), followed by B. lituricollis (n = 25). Other species included B. karnyi and B. sauteri. Although females of B. bisignata and B. lituricollis cannot be differentiated unequivocally on morphological traits, cuticular hydrocarbon profiles were markedly different, one profile clearly resembling those of male B. lituricollis. Patterns also were consistent among nymphal stages. Both species were found in dense ground covers of leaf litter and mulches in urban or rural settings, and in pure or mixed populations. Hydrocarbon profiles of B. bisignata from Hong Kong and Laos were consistent with those from Taiwan, based on ANOVA of KI (Kovats. Indices) 3010 and KI 3040 peak areas. These peaks comprise part of a novel homologous series of di, tri- and tetramethyl alkanes. Some geographic variation in specimens of B. lituricollis from Hawaii and Taiwan was noted. Chemotaxonomy has several advantages over traditional taxonomic procedures in separating closely-related species, or in identifying life stages when no morphology-based keys exist.