The Key fits the Lock

A pair of Chalk Hill Blue butterflies (Polyommatus coridon) mate on a stem of grass at Warham, Norfolk, England. Their genitals are clearly visible locking them together in the act of coitus. This bond is so strong that if disturbed they can take flight still attached to each other. Lepidoptera have some of the most complex genital structures of all insects. The uniqueness of these organs to specific species led to one of the most important keys in taxonomic identification. With the advent of DNA analysis this has now become just one of the techniques used in taxonomy. The genitalia in male and female, of any particular Lepidopteran, species are adapted to fit each other like a lock (female) and key (male). This unique arrangement of genitalia is important in courtship and mating as it prevents cross-specific mating and hybridisation.