Subimago
Guides
Ephemeroptera
mayflies, Canadian soldiers, shadflies, fishflies, up-winged flies
Mayflies (Ephemeroptera) represent the oldest known winged insects, with fossil evidence dating to approximately 350 million years ago in the lower Carboniferous. The order contains over 3,000 described species across more than 400 genera and 42 families worldwide. Adults are characterized by short lifespans—typically hours to days—and a unique subimaginal stage where the winged but sexually immature subimago undergoes a final molt to become a reproductive imago. Larvae are exclusively aquatic and serve as important indicators of water quality in freshwater ecosystems.
Isonychia intermedia
Isonychia intermedia is a species of mayfly in the family Isonychiidae. Like other members of its genus, it is an aquatic insect with a life cycle consisting of an extended nymphal stage in freshwater habitats followed by a brief adult stage. The species is found in North America and is part of the EPT (Ephemeroptera-Plecoptera-Trichoptera) assemblage used in water quality biomonitoring. Adults are known to anglers as 'slate drakes' due to their dark wing coloration.
Maccaffertium
flatheaded mayflies
Maccaffertium is a genus of mayflies in the family Heptageniidae, commonly known as flatheaded mayflies. The genus was established by Bednarik in 1979 and contains approximately 19–20 described species. Like other members of Heptageniidae, these mayflies are characterized by their flattened, streamlined bodies adapted for life in flowing water. The genus is found in North America, with species distributed across various freshwater habitats.
Maccaffertium luteum
Maccaffertium luteum is a species of flat-headed mayfly in the family Heptageniidae, originally described by Clemens in 1913. The genus Maccaffertium was historically treated as a subgenus of Stenonema but was elevated to full generic status based on morphological and phylogenetic studies. Like other members of its family, this species exhibits the characteristic subimago stage—a sexually immature winged form unique to mayflies that requires one final molt to reach reproductive adulthood.
Maccaffertium mediopunctatum
flat-headed mayfly
Maccaffertium mediopunctatum is a species of flat-headed mayfly in the family Heptageniidae. It occurs in Southeastern Canada and the Eastern United States. The species has two recognized subspecies: M. m. arwini and M. m. mediopunctatum. Like other members of its genus, it exhibits the unique mayfly developmental trait of having a fully winged subadult stage (subimago) that requires one additional molt to reach sexual maturity.
Maccaffertium mediopunctatum arwini
A subspecies of mayfly in the family Heptageniidae. Like other members of its genus, it exhibits the characteristic subimago stage—fully winged but sexually immature—unique among insects. Adults are short-lived, emerging from aquatic habitats to mate. The subspecific epithet honors an individual, following the pattern of other Maccaffertium subspecies.
Maccaffertium mediopunctatum mediopunctatum
Maccaffertium mediopunctatum mediopunctatum is a subspecies of mayfly in the family Heptageniidae. The genus Maccaffertium was established to accommodate species formerly placed in Heptagenia and related genera, distinguished by particular features of the male genitalia and wing venation. This subspecies is part of a group of flatheaded mayflies commonly found in North American streams and rivers. Subimagos (subadults) of this species exhibit the characteristic pale, milky-white coloration and opaque wings typical of the genus, with sexual dimorphism in eye size and abdominal claspers.
Maccaffertium meririvulanum
fresh flat-headed mayfly
Maccaffertium meririvulanum is a species of flatheaded mayfly in the family Heptageniidae, characterized by its distinctive flattened head morphology typical of this group. The species is known from North America, where it inhabits freshwater lotic environments. As with other members of the genus, it undergoes the unique mayfly developmental pattern involving a winged subadult (subimago) stage that molts once more to reach sexual maturity.
Maccaffertium mexicanum
flatheaded mayfly
A flatheaded mayfly species in the family Heptageniidae. Adults are attracted to light sources near aquatic habitats. The species possesses the unique mayfly trait of developing fully functional wings during the subimago (sub-adult) stage, requiring one additional molt to reach sexual maturity. Two subspecies are recognized: M. m. integrum and M. m. mexicanum.
Maccaffertium mexicanum integrum
Maccaffertium mexicanum integrum is a subspecies of mayfly in the family Heptageniidae. Like other members of its order, it undergoes a unique developmental process involving a winged subadult stage (subimago) that molts once more before reaching sexual maturity. The subspecies has been documented in the Nearctic and Neotropical regions, with observations from the Mississippi River lowlands of southeastern Missouri.
Maccaffertium pudicum
flatheaded mayfly
Maccaffertium pudicum is a species of flatheaded mayfly in the family Heptageniidae. It is found in North America. The species exhibits the characteristic subimago stage typical of mayflies, where fully functional wings develop before the final molt to adulthood.
Maccaffertium terminatum
flatheaded mayfly
Maccaffertium terminatum is a species of flatheaded mayfly in the family Heptageniidae. It is widely distributed across Canada and the Nearctic region. The species possesses the characteristic subimago stage typical of mayflies, where sexually immature adults with opaque, milky-white wings emerge from water before undergoing a final molt to the reproductive adult stage. Two subspecies are recognized: M. t. terminatum and M. t. placitum.
Maccaffertium terminatum placitum
Maccaffertium terminatum placitum is a subspecies of mayfly in the family Heptageniidae. Like other members of the genus, it exhibits the unique mayfly developmental trait of having a functional winged sub-adult stage (subimago) prior to the final molt to sexual maturity. The subimago is characterized by milky-white, opaque wings and paler body coloration compared to the transparent-winged adult. This subspecies is part of the Nearctic fauna of North America.
Maccaffertium terminatum terminatum
Maccaffertium terminatum terminatum is a subspecies of mayfly in the family Heptageniidae. Like other members of its genus, it exhibits the unique mayfly developmental trait of having a winged sub-adult stage (subimago) that requires one final molt to reach full adulthood. The subspecies is part of the Nearctic fauna, with records from North America. As an aquatic insect, its life cycle is tied to freshwater habitats, with nymphs developing in water before emerging as winged adults.
Timpanoga hecuba
Great Red Quill
Timpanoga hecuba, commonly known as the Great Red Quill, is a species of mayfly in the family Ephemerellidae. This Nearctic species is significant in fly fishing, where its adult and subimago (dun) forms are imitated by artificial flies. The species was originally described as Ephemerella hecuba by Eaton in 1884 and later transferred to the genus Timpanoga.