Morphological diagnosis of six Liriomyza species (Diptera: Agromyzidae) of quarantine importance in Taiwan

Liriomyza leafminers comprise a pest group that causes both considerable economic losses and serious quarantine problems. In this study, morphological studies were performed to assist in the species identification and discrimination of six Liriomyza pest species of quarantine importance: L. brassicae, L. bryoniae, L. chinensis, L. huidobrensis, L. sativae, and L. trifolii. The discriminative ability of some traditional morphological characters, such as abdominal color patterns and mate genitalia, was re-evaluated. In addition, electronmicrographic and geometric morphometric methods were introduced for separating different species. Illustrative plates of the preceding morphology were collated into mappings for further applications in quarantine inspection; some analyses and evaluations in separating similar species are also discussed in further detail. The results show that the abdominal color patterns can only separate two species from others; nevertheless, the ultrastructures of the thoracic microsetae and male genitalia are useful morphological characters to prevent misidentifications. On each species, the thoracic microsetae show their unique arrangement and pattern in both length and density; meanwhile, photography of male genitalia using a larger focal depth was also proven to be taxonomically valuable in practice. Although not all pairs between any two species have significant differences in wing shape, wing morphometric results do reveal that the most variant area of wing shape is located around the cross veins; this suggests that the morphology of this area might be easily and efficiently used for differentiating these species.