Eastern Forktail

Ischnura verticalis — the eastern forktail — is the most widespread and most ABUNDANT damselfly in eastern North America and one of the most-cited examples of female color polymorphism in damselfly biology. The species is widespread across all of eastern and central North America from southern Canada south through the eastern US to Mexico, and is present at essentially every pond, marsh, and slow stream within its range — often in tens-to-hundreds of individuals per pond margin. Adults are 24-33 mm body length, very slim and delicate damselflies. Males are dark with green-and-black thoracic stripes, dark abdomens, and a distinctive BRIGHT BLUE TAIL TIP on the eighth and ninth abdominal segments (the source of the species name 'verticalis' — referring to the vertical line of blue at the abdomen tip). Females exhibit one of the most-cited examples of FEMALE COLOR POLYMORPHISM in damselflies — three distinct color morphs that change with age and reproductive status: (1) IMMATURE FEMALES are bright ORANGE — the conspicuous coloration is correlated with sexual immaturity (so males do not waste energy attempting to mate with immature individuals); (2) MATURE HETEROCHROMATYPIC FEMALES are dull GRAY — the cryptic coloration provides camouflage during egg-laying; (3) MATURE ANDROCHROMATYPIC FEMALES are BLUE-AND-BLACK like the males — the male-mimicry coloration provides protection from harassment by males during foraging (males that approach androchromatypic females mistake them for other males and are repelled by territorial responses, allowing the female to forage and oviposit without constant disruption). The androchromatypic morph is one of the most-cited examples of female-mimics-male sexual mimicry in arthropod biology and is a flagship case study in evolutionary studies of sexual conflict. Eastern forktails are equally important ecologically as MOSQUITO PREDATORS — adults consume small flying insects (especially mosquitoes, midges, gnats), and naiads consume mosquito larvae and other small aquatic invertebrates over a 1-year aquatic development period. The species is one of the most widespread and most ecologically important damselflies in eastern North American freshwater habitats.