Females of B. flaviventris are morphologically closely similar to those of B. sibiricus , but differ in having the orange pubescence dorsally between the wing bases and on gastral terga IV-VI replaced with black. Wang and J. Yao have kindly shown me the male of B. flaviventris , which is again closely similar in its male genitalia to B. sibiricus . B. ochrobasis appears to differ from B. flaviventris only in the lighter hue of the yellow pubescence of B. ochrobasis . At present I know of no good biological reason why these three nominal taxa should not be regarded as conspecific.
More evidence is awaited.
This convention has since changed and recent authors have consistently used s . Oriental, Palaearctic Regions. Several of these nominal taxa have been treated as separate species. B. heicens, B. huangcens, B. flavicollis and B. baichengensis are morphologically closely similar to B. asiaticus and differ only in details of the colour pattern. Until more evidence to the contrary is available from critical studies of patterns of variation, I shall treat them as parts of a single variable species.