, 0 0 0 ▁years . ▁Today , ▁five ▁sub species ▁of ▁the ▁blue ▁w ilde be est ▁are ▁recogn ised , ▁while ▁the ▁black ▁w ilde be est ▁has ▁no ▁named ▁sub species . ▁ ▁Gen et ics ▁and ▁hy br ids ▁The ▁dip lo id ▁number ▁of ▁chrom os om es ▁in ▁the ▁w ilde be est ▁is ▁ 5 8 . ▁Ch rom os om es ▁were ▁studied ▁in ▁a ▁male ▁and ▁a ▁female ▁w ilde be est . ▁In ▁the ▁female , ▁all ▁except ▁a ▁pair ▁of ▁very ▁large ▁sub met acent ric ▁chrom os om es ▁were ▁found ▁to ▁be ▁ac ro cent ric . ▁Met aph ases ▁were ▁studied ▁in ▁the ▁male ' s ▁chrom os om es , ▁and ▁very ▁large ▁sub met acent ric ▁chrom os om es ▁were ▁found ▁there , ▁as ▁well , ▁similar ▁to ▁those ▁in ▁the ▁female ▁both ▁in ▁size ▁and ▁morph ology . ▁Other ▁chrom os om es ▁were ▁ac ro cent ric . ▁The ▁X ▁chrom os ome ▁is ▁a ▁large ▁ac ro cent ric ▁and ▁the ▁Y ▁chrom os ome ▁a ▁minute ▁one . ▁ ▁The ▁two ▁species ▁of ▁the ▁w ilde be est ▁are ▁known ▁to ▁hy brid ise . ▁Male ▁black ▁w ilde be est ▁have ▁been ▁reported ▁to ▁mate ▁with ▁female ▁blue ▁w ilde be est ▁and ▁vice ▁vers a . ▁The ▁differences ▁in ▁social ▁behaviour ▁and ▁habit ats ▁have ▁histor ically ▁prevent ed ▁inter specific ▁hy brid isation ▁between ▁the ▁species , ▁but ▁hy