▁but ter fly , ▁which ▁is ▁a ▁su pers pecies ▁that ▁is ▁further ▁divided ▁into ▁three ▁sub species . ▁ ▁Some ▁authors ▁apply ▁the ▁term ▁to ▁a ▁species ▁with ▁in tras pec ific ▁vari ability , ▁which ▁might ▁be ▁a ▁sign ▁of ▁on going ▁or ▁in cip ient ▁spe ci ation . ▁Ex amples ▁are ▁ring ▁species ▁or ▁species ▁with ▁sub species , ▁in ▁which ▁it ▁is ▁often ▁unclear ▁if ▁they ▁should ▁be ▁considered ▁separate ▁species . ▁ ▁Rel ated ▁concepts ▁ ▁Several ▁terms ▁are ▁used ▁syn onym ously ▁for ▁a ▁species ▁complex , ▁but ▁some ▁of ▁them ▁may ▁also ▁have ▁slightly ▁different ▁or ▁nar ro wer ▁mean ings . ▁In ▁the ▁nom en cl ature ▁codes ▁of ▁zo ology ▁and ▁b acter i ology , ▁no ▁tax onom ic ▁ranks ▁are ▁defined ▁at ▁the ▁level ▁between ▁sub gener a ▁and ▁species , ▁but ▁the ▁botan ical ▁code ▁defines ▁four ▁ranks ▁below ▁gener a ▁( section , ▁sub sections , ▁series ▁and ▁sub series ). ▁D ifferent ▁inform al ▁tax onom ic ▁solutions ▁have ▁been ▁used ▁to ▁indicate ▁a ▁species ▁complex . ▁ ▁Ident ification ▁ ▁Dist ingu ishing ▁close ▁species ▁within ▁a ▁complex ▁requires ▁the ▁study ▁of ▁often ▁very ▁small ▁differences . ▁Mor ph ological ▁differences ▁may ▁be ▁minute ▁and ▁visible ▁only ▁by ▁the ▁use ▁of ▁adapted ▁methods , ▁such ▁as ▁micro sc opy . ▁However , ▁distinct ▁species ▁sometimes ▁have ▁no ▁morph ological ▁differences . ▁In ▁those ▁cases , ▁other ▁characters , ▁such ▁as ▁in ▁the ▁species ' ▁life ▁history ,