Insignificant Small Minnow Mayfly (Procloeon insignificans)
The Insignificant Small Minnow Mayfly was described in 1925; it is known only from its type locality which is somewhere in the vicinity of the city of Ottawa in Ontario, Canada.
“MALE. – Length of body 3mm., of fore wing 4 mm. Thoracic notum and pleura dark brown, sternum lighter brown, legs white, and wings hyaline, with longitudinal veins faintly yellowish. Basal abdominal tergites white, with a faint red, median streak on tergites 2 and 3, sternites 2 and 3 white; apical tergites light brown, sternites tan; genital forceps and caudal filaments white.” 
The species was never found since and is likely extinct now.
 B. D. Burks: The mayflies, or Ephemoptera, Of Illinois. Illinois Natural History Bulletin 26: 1-216. 1953-1955
Staudinger’s Owlet Moth was described in 1862, the species is known only from the coast of the Labrador peninsula, Canada
The species was never recorded since and may indeed be extinct, yet, apparently not many lepidopterologists have ever collected at Labrador’s coasts, so there is some chance that this species might still be extant.
This species was described in 1984 based on specimens from Kettle- and Okanagan Valleys in British Columbia, Canada.
The species appears to be lost or even extinct, on the other hand it might not be valid after all but might turn out to be identical with the Red-shanked Grasshopper (Xanthippus corallipes (Haldeman)) (see photo).
 James W. Miskelly: Updated checklist of the Orthoptera of British Colombia. Journal of the Entomological Society of British Columbia 109: 24-29. 2012
The Rocky Mountain Locust inhabited a large range., including Alberta, Manitoba, and Saskatchewan in Canada and Arizona, Colorado, Iowa, Kansas, Minnesota, Montana, Nebraska, North Dakota, Texas, and Wyoming in the USA.
The full-grown adults reached lengths of about 3 cm.
The species formerly formed seasonally swarms of giant sizes, which then devastated large areas of North America, destroying countless crops, and causing famines.
It is said that the locust plague did not spared cotton clothing or leather when found, and it is furthermore claimed, that they may have even eaten wooden fencing posts.
These last assertions, however, are probably pure fantasy.
The last large swarms were recorded in the years between 1873 and 1877, the last specimens were finally collected in Manitoba, Canada in 1902.
The reasons for the extinction of this once so common species are not well known, but it has been argued that plowing and irrigation by settlers in the Great Plains disrupted their natural life cycle in the areas they lived in, so it is reported that farmers destroyed over 150 egg cases per square inch while plowing, harrowing or flooding. 
 Jeffrey A. Lockwood: Locust: The Devastating Rise and Mysterious Disappearance of the Insect that Shaped the American Frontier. New York: Basic Books 2004
The Dragon Lake is a 2,25 km² resp. 225 ha large lake in British Columbia, it is a popular destination for anglers and well known for its large rainbow trouts (Oncorhynchus mykiss (Walbaum)) – however, that wasn’t always so.
The lake was once the home for two sympatric whitefish species – both species have never been described, and both species fell victim to a so called ‘lake rehabilitation’ in the year 1956.
The term ‘rehabilitaion’ disguises the pervert idea, to reshape a lake appropriate for so called game fishes by using insecticides like rotenone and toxaphene, both of which are simply deadly for fishes, to exterminate all living things, so that, later, when the poisons have vanished from the water of the now dead lake, the desired game fishes can be introduced – in the case of the Dragon Lake rainbow trouts.
The Dragon Lake Whitefish was similar to the Lake Whitefish (Coregonus clupaeformis (Mitchill)), but differed from this species in the number of its gill rakers.
The Dark-banded Flower Gem Moth was described in 1874, a somewhat enigmatic species being the sole member of its genus.
The biology of this species, including the larval host plant/plants, is completely unknown. It appears, however, to have been restricted to a certain type of prairie habitat which today is highly reduced.
The species was last recorded during the 1970s with some records from Canada, others from North Dakota, USA, it is classified as ‘Data Deficient’ but may in fact already be extinct.
The Eelgrass Limpet aka. Bowl Limpet was described in 1831; it lived in the western Atlantic Ocean and was once quite common and widespread, having been found from Labrador in Canada as far south as New York, USA.
The species was adapted to inhabit the leaf blades of Eelgrass (Zostera marina L.); large parts of the eelgrass colonies along the western Atlantic coastlines suddenly died in the early 1930s by a disease caused by a slime mold. The eelgrass survived only because some populations inhabited brackish water into which the mold could not spread; the limpet, however, was not able to adapt to brackish water and thus the whole species died out due to the complete loss of its only habitat and host.
The Eelgrass Limpet was last seen in 1929 but was declared extinct only in 2000; another subspecies, the Pacific Eelgrass Limpet (Lottia alveus ssp. parallella (Dall)) (see photo), still survives in the waters of the northern Pacific Ocean.
The plant is only known from two (or three) historical collections from the 1860s.
The original collection sites, swampy areas east of Belleville, a city near Ottawa, where it was found growing on elm trees, were cleared and the species has not been relocated despite considerable bryological fieldwork in the region, and thus is considered most likely extinct.
 Robert R. Ireland: Neomacounia, a new genus in the Neckeraceae (Musci) from Canada. The Bryologist 77(3): 453-459. 1974