For example , some species in the genera Erynnis , Hesperia , and Amblyscirtes can not currently be distinguished in the field by experts , the only reliable method of telling them apart involving dissection and examination of the genitalia . For example , some species in the genera Amblyscirtes , Erynnis ( duskywings ) and Hesperia ( branded skippers ) can not currently be distinguished in the field even by experts . The only reliable method of telling them apart involving dissection and microscopic examination of the genitalia which have characteristic structures that prevent mating except between conspecifics .