Some morphological species are composed of several cytological sibling species. For example, Simulium tani and S. doipuiense are composed of 10 and 2 cytoforms, respectively, (Tangkawanit et al. 2009) and S. siamense
is composed of 7 cytoforms (Kuvangkadilok et al. 2008; Pramual and Wongpakam 2011). Although these studies
indicate the importance of cytogenetics for black fly taxonomy, only 18 of 88 species in Thailand have been cytologically
examined. DNA barcodes have been used to differentiate morphological species of black flies in Thailand. The results indicate that this method could be used successfully to differentiate morphologically distinct species and to reveal cryptic diversity (Pramual et al. 2011b; Pramual and Nanork 2012), but it can fail to delineate cytological sibling species (Pramual et al. 2011a)