Presentation on theme: "A meteorological and entomological investigation."— Presentation transcript:
A meteorological and entomological investigation
Motivation From St. Cloud Visitors Guide: Grasshopper Chapel: The Chapel represents the miracle of an 1877, April 26 snowstorm that halted an impending grasshopper plague. Many print and Web documents assert that a spring snowstorm and cold weather destroyed the grasshoppers Question: was there really such a spring snowstorm, and what effect might it have had?
Actually, two versions of chapels origins exist Version 1: late spring snowstorm killed off grasshoppers; chapel built in thanksgiving Version 2: weather not a factor; local parishioners seeking divine assistance in ending grasshopper plague promised to build chapel and hold services there for 15 years
First, a look at the grasshopper plague of the 1870s Starting in 1873, farmers in Minnesota were severely affected by successive infestations of grasshoppers
Meet the Rocky mountain locust (Melanoplus spretus) No photos from life since its long extinct (1902) This species resembled the common grasshopper but was called a locust because of its migratory behavior. 20-35 mm on average
Migratory locust swarms could cover thousands of square miles
Reports of the insects eating every green thing Even known to eat holes in clothing and chew wooden tool handles Great hardship resulted; many pioneers were already living a life of subsistence Some families abandoned their claims Men went east to find work
In "The Funston Homestead (Kansas), Ella Eckdall writes: All was going well on the farm and Father's hopes were high until one morning in the spring of 1874, when great black, threatening clouds rolled in from the west. The landscape suddenly darkened, and from the dark mass great hordes of grasshoppers descended upon the growing fields. They voraciously devoured every green thing above the ground. Not a spear of grass nor a leaf upon tree or plant was left to mark the once verdant herbage.
Laura Ingalls Wilder gave an description consistent with other pioneer accounts 1874-76 homestead in Redwood County, Minnesota She describes the insects devouring the field and garden crops (with the sound of ''millions of jaws biting and chewing')
Examples of crop damage Oats damaged by lesser migratory locusts Wheat field damaged by Australian plague locusts
Control was difficult if not impossible No pesticides were available Various tactics were tried capture smoke burning ditches hopperdozers
Original chapel probably looked something like this one, a second grasshopper chapel built in the same summer, just south of St Cloud
Evidence for Version 1 (snowstorm) Official Army Signal Corps records are few; observers at widely scattered sites Fort Ripley data (50 miles north of St Cloud) is bad Reports on a widespread late April storm with snow, sleet, and rain found in newspapers
St. Paul observations Apr 24, 1877 55 36 Apr 25, 1877 62 40 Apr 26, 1877 56 45 Apr 27, 1877 46 33 Apr 28, 1877 39 32 0.13/0.25 melted Apr 29, 1877 45 30 Apr 30, 1877 54 26 May 1, 1877 60 37 Mean almost 2 SD below average
But are snow and (possibly) subfreezing temperatures injurious to grasshoppers?
Life cycle of the grasshopper Eggs laid in late summer or fall Overwinter in ground Hatching in early May Nymphs develop wings after 40-60 days Adults can then fly to a new area and lay eggs to repeat the cycle
Effects of cold on grasshopper nymphs Studies of related species such as Melanoplus sanguinipes show that warm early spring with premature hatch followed by cold snap poor development of nymphs cloudy, wet weather favors occurrence of disease inhibits feeding and results in high mortality
What of a short, near freezing period? Many insects exhibit cold hardening (they accumulate sugars to prevent tissue freezing; locusts may have had this capacity. Air temperature of 32°F is not generally lethal to grasshoppers, as they often shelter. Hemolymph and tissues of insects include salts and carbohydrates that would prevent freezing (and lethality) at this temperature. Grasshoppers can certainly survive temperatures in the 20s (Lockwood, personal communication).
Observations at the time? Newspaper accounts record varying opinions, but observations showed the storm had little or no effect on the insects
Point may be moot: had eggs even hatched in central Minnesota? Again we rely on newspaper reports While hatching had commenced in southern Minnesota, only a few eggs had hatched in the St. Cloud area by the time of the storm
Evidence for grasshopper damage in the summer of 1877 Many newspaper reports from area Archived statement of Fr. Leo Winter (pastor of the parishioners building the Cold Spring chapel) Wheat yields for Stearns County 1875187618771878 Acres39600460004870057900 Bushels572600384100143800902000 Bu/ac14.58.352.9515.8
1877 was the last year of the grasshopper plague in Minnesota (and elsewhere) They flew but didnt land to lay eggs Why? Disease, parasites, or cool and wet June may have taken a toll Fate unknown Migration back to Rockies?
Population dynamics Current population models show success in predicting population increases, but cannot predict population crashes Latter are influenced by weather, and long-range weather forecasting is poor (as we know!)
Conclusions Recall the two versions of the Grasshopper Chapels origin: Version 1: late spring snowstorm kills off grasshoppers Version 2: weather not a factor in disappearance Strong evidence indicates Version 2 is the true story