The Rocky Mountain locust (Melanoplus spretus) is an extinct species of grasshopper that ranged through the western half of the United States and some western portions of Canada with large numbers seen until the end of the 19th century. Sightings often placed their swarms in numbers far larger than any other locust species, with one famous sighting in 1875 estimated at in size (greater than the area of California), weighing 27.5 million tons and consisting of some 12.5 trillion insects, the greatest concentration of animals ever recorded, according to Guinness World Records. Walsh does not provide a description of the species, except for female wing length, as well as some aspects of biology, ecology, and control. Some entomologists credit the authority for the binomial Caloptenus spretus to C. Thomas, but fails on the Principle of Priority. The treatment under the genus Melanoplus began in 1878 in publications by S. H. Scudder who pointed out the difference between the genus Caloptenus that he noted as being more correctly spelled Calliptenus and Melanoplus.
The species is reported to have descended from the Rocky Mountains to the prairie in large numbers only in certain years, particularly in dry seasons, following westward wind currents. Outbreaks usually lasted two consecutive years. Although a great number of eggs were laid on the prairie during outbreak years, individuals hatched from these eggs usually did not thrive, a condition that has been attributed to the lack of adaptation of this species to prairie habitats.
Distribution and habitat
thumb|Illustration of egg-laying by females (1877)
The Rocky Mountain locust occurred along both sides of the Rocky Mountains and in most of the prairie areas. Breeding in sandy areas and thriving in hot and dry conditions, it has been hypothesized that they may have depended on the tall grass prairie plants during drier spells. The destruction of the prairie habitat and the incursion of new flora and fauna along with agricultural practices may have led to the extinction of the species. Large numbers of grasshoppers including a large number of Rocky Mountain locusts entombed in the ice in the Rocky Mountains gave their name to the Grasshopper Glacier.
History
Rocky Mountain locusts became more of a problem in the 19th century, as farming expanded westward into the grasshoppers' favored habitat. Outbreaks of varying severity emerged in 1828, 1838, 1846, and 1855, affecting areas throughout the West. Plagues visited Minnesota in 1856–1857 and again in 1865, and Nebraska suffered repeated infestations between 1856 and 1874.
James Fletcher collected a male and female spretus in July 1901 and Norman Criddle did the same in July 1902, both in Manitoba. Morgan Hebard collected three specimens in August 1904, in Colorado, commenting on the difficulty of finding spretus examples in the Rockies.
Melanoplus spretus was formally declared extinct by the IUCN in 2014. The justification did not mention the 2004 DNA investigation.
Theories for extinction
It has been hypothesized that the removal of prairie grasses which were maintained by native herbivores such as bison were important for maintaining the main breeding habitat of the locust. while the permanent breeding grounds of this species seemed to be restricted to an area somewhere between of sandy soils near streams and rivers in the Rockies, which coincided with arable and pastoral lands exploited by settlers.
Related species and taxonomic issues
One theory proposed was that M. spretus was not a distinct species in the first place and that it might have been a migratory phase, differing slightly in morphology, from a species that may still be extant. M. spretus is similar in appearance based on morphology to a migratory form of M. sanguinipes and the two had been suggested to be sister taxa (closest living relatives).
In culture
thumb|Inscription above the door of the Grasshopper Chapel
Assumption Chapel in Cold Spring, Minnesota, was established as a Christian pilgrimage shrine () () in 1877 by German-American Catholic pioneer farmers, supposedly to keep away future locust plagues similar to those they had faced in both the 1850s and the 1870s. The Feast Day of St. Magnus of Füssen, September 6, was locally celebrated as "Grasshopper Day" because St. Magnus of Füssen is traditionally known in Southern Germany as one of the protectors of farmers from thunderstorms and plagues of vermin.
The 1877 pilgrimage chapel dedicated to St. Boniface in nearby St. Augusta, Minnesota dates from the same era and was built for exactly the same reason. There is a similar local tradition of pilgrimages to the shrine on June 5th, the Feast Day of St. Boniface, an English Benedictine missionary, Bishop, and martyr instrumental to the Christianisation of the Germanic peoples; and who is still revered as the "Apostle to the Germans", Patron Saint of the Germanosphere and the German diaspora.
A semi-fictionalized description of the devastation created by Rocky Mountain locusts in the 1870s can be found in the semi-autobiographical novel On the Banks of Plum Creek by Laura Ingalls Wilder. Her description was based on actual incidents in western Minnesota during the summers of 1874 and 1875 as the locusts destroyed her family's wheat crop.
See also
- Locust Plague of 1874
- List of recently extinct insects
- Mormon cricket – another large, swarming orthopteran native to western North America
- Passenger pigeon – another example of rapid anthropogenic extinction of a North American species