Many species are not isolated from other species by shape or territory
, but by mating behaviour
. North American fireflies
are a classic example of a group (the genus Photuris
) in which many of the species
are physically almost indistinguishable. The only major difference between most of these species is in the frequency of the males' flash patterns when attempting to attract mates.
This is not an insignificant detail. It separates the species as surely as any morphological difference. In many places, two or three Photuris species may share the same territory, but are pevented from interbreeding by the courtship behaviours they display. Photuris potomaca flashes very short blips of light every second or so; Photuris lucicrescens flashes only every seven seconds, and its flashes last almost two seconds. Other species display wavering flashes, dot-dash patterns, and different colours in their flashes. Of 18 Photuris species studied by Herbert S. Barber in 1951, only two species displayed the same flash patterns, and these species were quite different morphologically, and inhabited separate territories.